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The Objective Caml system release 2.04 - The Caml language

1. Genlex token Kwd Stream next token_stream Genlex token Ident x The parser itself operates by pattern matching on the stream of tokens As usual with re cursive descent parsers we use several intermediate parsing functions to reflect the precedence and associativity of operators Pattern matching over streams is more powerful than on regular data structures as it allows recursive calls to parsing functions inside the patterns for matching sub components of the input stream See chapter 6 for more details let rec parse_expr parser lt e1 parse_mult e parse_more_adds e1 gt gt e and parse_more_adds e1 parser lt Kwd e2 parse_mult e parse_more_adds Sum e1 e2 gt gt e N N lt Kwd e2 parse_mult e parse_more_adds Diff e1 e2 gt gt e lt gt gt e1 and parse_mult parser lt e1 parse_simple e parse_more_mults e1 gt gt e and parse_more_mults e1 parser lt Kwd e2 parse_simple e parse_more_mults Prod e1 e2 gt gt e lt Kwd e2 parse_simple e parse_more_mults Quot e1 e2 gt gt e lt gt gt e1 and parse_simple parser lt Ident s gt gt Var s lt Int i gt gt Const float i lt Float f gt gt Const f lt Kwd e parse_expr Kwd gt gt e val parse_expr Genlex token Stream t gt expression lt fun gt val parse_m
2. Euro c operation list Deposit lt obj gt Retrieval lt obj gt Closing an account can be done with the following polymorphic function let close c c withdraw c balance val close lt balance a withdraw a gt b gt gt b lt fun gt Of course this applies to all sorts of accounts Finally we gather several versions of the account into a module Account abstracted over some currency let today 01 01 2000 an approximation module Account M MONEY struct type m M c let m new M c let zero m 0 class bank object self HH HOH OH Chapter 4 Advanced examples with classes and modules 61 val mutable balance zero method balance balance val mutable history method private trace x history lt x history method deposit x self trace Deposit x if zero leq x then balance lt balance plus x else raise Invalid_argument deposit method withdraw x if x leq balance then balance lt balance plus neg x self trace Retrieval x x else zero method history List rev history end class type client_view object method deposit m gt unit method history m operation list method withdraw m gt m method balance m end class virtual check_client x let y if m 100 leq x then x else raise Failure Insufficient initial deposit in object self initializer self deposit y end module Client B sig class bank
3. 10 4 Compatibility with the bytecode compiler This section lists the known incompatibilities between the bytecode compiler and the native code compiler Except on those points the two compilers should generate code that behave identically e The following operations abort the program either by printing an error message or just via an hardware trap or fatal Unix signal instead of raising an exception integer division by zero modulus by zero stack overflow on the Alpha processor only floating point operations involving infinite or denormalized numbers all other processors supported by ocamlopt treat these numbers correctly as per the IEEE 754 standard In particular notice that stack overflow caused by excessively deep recursion is reported by most Unix kernels as a segmentation violation signal e Signals are detected only when the program performs an allocation in the heap That is if a signal is delivered while in a piece of code that does not allocate its handler will not be called until the next heap allocation The best way to avoid running into those incompatibilities is to never trap the Division_by_zero and Stack_overflow exceptions thus also treating them as fatal er rors with the bytecode compiler as well as with the native code compiler Test the divisor before performing the operation instead of trapping the exception afterwards 140 Chapter 11 Lexer and parser generators ocamllex oc
4. 301 302 Windows This library is available only under the toplevel application ocamlwin exe Before using it the Caml part of this library must be loaded in core either by typing load graphics cmo in the input windows or by using the Load entry of the File menu The screen coordinates are interpreted as shown in the figure below Notice that the coordinate system used is the same as in mathematics y increases from the bottom of the screen to the top of the screen and angles are measured counterclockwise in degrees Drawing is clipped to the screen y Screen pixel at x y x size_x 22 1 Module Graphics machine independent graphics primitives exception Graphic_failure of string Raised by the functions below when they encounter an error Initializations val open_graph string gt unit Show the graphics window or switch the screen to graphic mode The graphics window is cleared and the current point is set to 0 0 The string argument is used to pass optional information on the desired graphics mode the graphics window size and so on Its interpretation is implementation dependent If the empty string is given a sensible default is selected val close_graph unit gt unit Delete the graphics window or switch the screen back to text mode val clear_graph unit gt unit Erase the graphics window Chapter 22 The graphics library 303 val size_x unit gt int val size
5. ENOENT ENOEXEC ENOLCK ENOMEM ENOSPC ENOSYS ENOTDIR ENOTEMPTY ENOTTY ENXIO EPERM EPIPE ERANGE EROFS ESPIPE ESRCH EXDEV Resource deadlock would occur Domain error for math functions etc File exists Bad address File too large Function interrupted by signal Invalid argument Hardware I O error Is a directory Too many open files by the process Too many links Filename too long Too many open files in the system No such device No such file or directory Not an executable file No locks available Not enough memory No space left on device Function not supported Not a directory Directory not empty Inappropriate I O control operation No such device or address Operation not permitted Broken pipe Result too large Read only file system Invalid seek e g on a pipe No such process Invalid link Additional errors mostly BSD EWOULDBLOCK EINPROGRESS EALREADY ENOTSOCK EDESTADDRREQ EMSGSIZE EPROTOTYPE ENOPROTOOPT EPROTONOSUPPORT ESOCKTNOSUPPORT EOPNOTSUPP EPFNOSUPPORT Operation would block Operation now in progress Operation already in progress Socket operation on non socket Destination address required Message too long Protocol wrong type for socket Protocol not available Protocol not
6. Input modes mutable mutable mutable mutable mutable mutable mutable mutable mutable mutable mutable Output mutable Control modes mutable mutable mutable mutable mutable mutable mutable mutable mutable c_ignbrk bool c_brkint bool c_ignpar bool c_parmrk bool c_inpck bool c_istrip bool c_inlcr bool c_igncr bool c_icrnl bool c_ixon bool c_ixoff bool modes c_opost bool c_obaud int c_ibaud int c_csize int c_cstopb int c_cread bool c_parenb bool c_parodd bool c_hupcl bool c_clocal bool Local modes Ignore the break condition Signal interrupt on break condition Ignore characters with parity errors Mark parity errors Enable parity check on input Strip 8th bit on input characters Map NL to CR on input Ignore CR on input Map CR to NL on input Recognize XON XOFF characters on input Emit XON XOFF chars to control input flow Enable output processing Output baud rate 0 means close connection Input baud rate Number of bits per character 5 8 Number of stop bits 1 2 Reception is enabled Enable parity generation and detection Specify odd parity instead of even Hang up on last close Ignore modem status lines Chapter 18 The unix library Unix system calls 277 mutab
7. To build the whole program just invoke the C compiler as follows cc o prog main c mod a 190 Part IV The Objective Caml library 191 Chapter 16 The core library This chapter describes the functions provided by the Objective Caml core library module module Pervasives This module is special in two ways e It is automatically linked with the user s object code files by the ocamlc command chapter 7 e It is automatically opened when a compilation starts or when the toplevel system is launched Hence it is possible to use unqualified identifiers to refer to the functions pro vided by the Pervasives module without adding a open Pervasives directive Conventions The declarations from the signature of the Pervasives module are printed one by one in typewriter font followed by a short comment All modules and the identifiers they export are indexed at the end of this report 16 1 Module Pervasives the initially opened module This module provides the built in types numbers booleans strings exceptions references lists arrays input output channels and the basic operations over these types This module is automatically opened at the beginning of each compilation All components of this module can therefore be referred by their short name without prefixing them by Pervasives Predefined types type int The type of integer numbers type char The type of characters 193 194 type t
8. an and builds the list f a1 f an with the results returned by f Not tail recursive val rev_map a gt b gt a list gt b list List rev_map f 1 gives the same result as List rev List map f 1 but is tail recursive and more efficient val fold_left Ca gt b gt a gt a gt b list gt a List fold_left f a b1 bn isf f a b1 b2 bn val fold_right a gt b gt b gt a list gt b gt b List fold_right f a1 an bisf a1 f a2 f an b Not tail recursive Iterators on two lists val iter2 a gt b gt unit gt a list gt b list gt unit List iter2 f a1 an b1 bn calls in turn f al b1 f an bn Raise Invalid_argument if the two lists have different lengths val map2 a gt b gt c gt a list gt b list gt c list List map2 f a1 an b1 bn is f a1 b1 f an bn Raise Invalid_argument if the two lists have different lengths Not tail recursive val rev_map2 a gt b gt c gt a list gt b list gt c list List rev_map2 f 1 gives the same result as List rev List map2 f 1 but is tail recursive and more efficient val fold_left2 a gt b gt c gt a gt a gt b list gt c list gt a List fold_left2 f a b1 bn c1 cn is f f a bi c1 b2 c2
9. and false are also constructor names The capitalization rules are summarized in the table below Name space Case of first letter Values lowercase Constructors uppercase Type constructors lowercase Record labels lowercase Classes lowercase Methods lowercase Modules uppercase Module types any 82 Referring to named objects value path value name module path lowercase ident cconstr cconstr name module path capitalized ident neconstr ncconstr name module path capitalized ident typeconstr typeconstr name extended module path lowercase ident label label name module path lowercase ident module path module name module path capitalized ident extended module path module name extended module path capitalized ident extended module path extended module path modtype path modtype name extended module path ident class path class name module path lowercase ident A named object can be referred to either by its name following the usual static scoping rules for names or by an access path prefix name where prefix designates a module and name is the name of an object defined in that module The first component of the path prefix is either a simple module name or an access path name name2g in case the defining module is itself nested inside other modules For referring to type constructors or module types the prefix can als
10. Chapter 22 The graphics library 307 Mouse and keyboard events type status mouse_x int X coordinate of the mouse mouse_y int Y coordinate of the mouse button bool true if a mouse button is pressed keypressed bool true if a key has been pressed key char the character for the key pressed To report events type event Button_down A mouse button is pressed Button_up A mouse button is released Key_pressed A key is pressed Mouse_motion The mouse is moved Poll Don t wait return immediately To specify events to wait for val wait_next_event event list gt status Wait until one of the events specified in the given event list occurs and return the status of the mouse and keyboard at that time If Poll is given in the event list return immediately with the current status If the mouse cursor is outside of the graphics window the mouse_x and mouse_y fields of the event are outside the range 0 size_x 1 0 size_y 1 Keypresses are queued and dequeued one by one when the Key_pressed event is specified Mouse and keyboard polling val mouse_pos unit gt int int Return the position of the mouse cursor relative to the graphics window If the mouse cursor is outside of the graphics window mouse_pos returns a point outside of the range 0 size_xQ 1 0 size_y 1 val button_down unit gt bool Return true if the mouse button i
11. bn cn Raise Invalid_argument if the two lists have different lengths val fold_right2 a gt b gt c gt c gt a list gt b list gt c gt c List fold_right2 f al an b1 bn cis f al b1 f a2 b2 f an bn c Raise Invalid_argument if the two lists have different lengths Not tail recursive Chapter 17 The standard library 237 List scanning val for_all a gt bool gt a list gt bool for_all p at an checks if all elements of the list satisfy the predicate p That is it returns p a1 amp amp p a2 amp amp amp amp p an val exists a gt bool gt a list gt bool exists p a1 an checks if at least one element of the list satisfies the predicate p That is it returns p a1 p a2 II p an val for_all2 a gt b gt bool gt a list gt b list gt bool val exists2 a gt b gt bool gt a list gt b list gt bool Same as for_all and exists but for a two argument predicate Raise Invalid_argument if the two lists have different lengths val mem a gt a list gt bool mem a 1 is true if and only if a is equal to an element of 1 val memg a gt a list gt bool Same as mem but uses physical equality instead of structural equality to compare list elements List searching val find a gt bool gt a list gt a f
12. event List iter fun x gt x notify self e observers end class a b subject object c constraint a lt notify c gt b gt unit gt val mutable observers a list method add_observer a gt unit method notify_observers b gt unit end The difficulty usually relies in defining instances of the pattern above by inheritance This can be done in a natural and obvious manner in Ocaml as shown on the following example manipulating windows type event Raise Resize Move type event Raise Resize Move let string_of_event function Raise gt Raise Resize gt Resize Move gt Move val string_of_event event gt string lt fun gt 70 let count ref 0 val count int ref fcontents 0 class observer window_subject let id count succ count count in object self inherit observer event subject val mutable position 0 method identity id method move x position lt position x self notify_observers Move method draw Printf printf Position 4d n position end class a window_subject object b constraint a lt notify b gt event gt unit gt val mutable observers a list val mutable position int method add_observer a gt unit method draw unit method identity int method move int gt unit method notify_observe
13. gt is the type of an object with methods and their associated types are described by method type method type and possibly some other methods represented by the ellipsis This ellipsis actually is a special kind of type variable also called row variable in the literature that stands for any number of extra method types types The type class path is a special kind of abbreviation This abbreviation unifies with the type of any object belonging to a subclass of class class path It is handled in a special way as it usually hides a type variable an ellipsis representing the methods that may be added in a subclass In particular it vanishes when the ellipsis gets instantiated Each type expression class path defines a new type variable so type class path gt class path is usually not the same as type class path as ident gt ident Variant and record types There are no type expressions describing variant types nor record types since those are always named i e defined before use and referred to by name Type definitions are described in sec tion 5 8 1 Chapter 5 The Objective Caml language 85 5 5 Constants constant integer literal float literal char literal string literal cconstr The syntactic class of constants comprises literals from the four base types integers floating point numbers characters character strings and constant constructors 5 6 Patterns pattern
14. pattern when expr gt expr pattern expr value name pattern typexpr expr infix symbol or amp 88 The table below shows the relative precedences and associativity of operators and non closed constructions The constructions with higher precedence come first For infix and prefix symbols we write x to mean any symbol starting with Construction or operator Associativity prefix symbol a fl function application left constructor application prefix E xx right ae hess mod left Fhe left i right O30 right comparisons lt etc all other infix symbols left not amp amp amp left or left lt right if right let match fun function try 5 7 1 Basic expressions Constants Expressions consisting in a constant evaluate to this constant Value paths Expressions consisting in an access path evaluate to the value bound to this path in the current eval uation environment The path can be either a value name or an access path to a value component of a module Parenthesized expressions The expressions expr and begin expr end have the same value as expr Both constructs are semantically equivalent but it is good style to use begin end inside control structures if then begin end else begin end and for the other grouping situations Parenthesized expressions can contain a type constraint a
15. set loadingmode direct The program is run directly by the debugger This is the default mode set loadingmode runtime The debugger execute the Objective Caml runtime camlrun on the program Rarely useful moreover it prevents the debugging of programs compiled in custom runtime mode set loadingmode manual The user starts manually the program when asked by the debugger Allows remote debugging see section 13 8 6 Chapter 13 The debugger ocamldebug 161 13 8 3 Search path for files The debugger searches for source files and compiled interface files in a list of directories the search path The search path initially contains the current directory and the standard library directory The directory command adds directories to the path Whenever the search path is modified the debugger will clear any information it may have cached about the files directory directorynames Add the given directories to the search path These directories are added at the front and will therefore be searched first directory Reset the search path This requires confirmation 13 8 4 Working directory Each time a program is started in the debugger it inherits its working directory from the current working directory of the debugger This working directory is initially whatever it inherited from its parent process typically the shell but you can specify a new working directory in the debugger with the cd command or the cd command line opti
16. 208 lt operator 196 lt operator 283 lt operator 196 lt operator 283 lt gt operator 196 lt gt operator 283 operator 196 operator 283 operator 196 gt operator 196 gt operator 283 gt operator 196 gt operator 283 operator 202 operator 200 operator 197 operator 197 operator 199 abs 198 abs_float 200 abs_num 283 accept 273 300 315 access 264 acos 199 add 231 245 310 add_available_units 312 add_buffer 215 add_channel 215 add_char 215 add_interfaces 311 add_num 282 add_string 215 add_substring 215 alarm 269 allow_unsafe_modules 312 always 298 append 213 235 approx_num_exp 284 approx_num_fix 284 Arg module 210 argv 253 arith_status 284 Arith_status module 284 array 248 Array module 212 asin 199 asr operator 198 Assert_failure exception 113 195 assoc 238 assq 238 at_exit 208 atan 199 atan2 199 background 303 Bad exception 212 basename 218 big_int_of_num 284 bind 273 bits 246 black 303 blit 213 252 256 blit_image 306 blue 303 316 bool_of_string 201 bounded_full_split 290 bounded_split 290 bounded_split_delim 290 bprintf 227 244 Break exception 255 broadcast 297 Buffer module 214 button_down 307 Callback module 216 capitalize 253 catch 243 catch_break 256 ceil 200 ceiling num 282 cha
17. Ca gt unit gt unit method length int method pop a method push a gt unit end let stack_fold s a stack3 f x let accu ref x in s iter fun e gt accu f accu e laccu val stack_fold a stack3 gt b gt a gt b gt b gt b lt fun gt 4 2 2 Hashtbl A simplified version of object oriented hash tables should have the following class type class type a b hash_table object method find a gt b method add a gt b gt unit end class type a b hash_table object method add a gt b gt unit method find a gt b end A simple implementation which is quite reasonable for small hastables is to use an association list class a b small_hashtbl a b hash_table object val mutable table method find key List assoc key table method add key valeur table lt key valeur table end class a b small_hashtbl a b hash_table H H H A better implementation and one that scales up better is to use a true hash tables whose elements are small hash tables class a b hashtbl size a b hash_table object self val table Array init size fun i gt new small_hashtbl method private hash key Hashtbl hash key mod Array length table method find key table self hash key find key method add key
18. ORDERED_TYPE gt SET module WrongStringSet WrongSet OrderedString module WrongStringSet sig type element WrongSet OrderedString element and set WrongSet OrderedString set val empty set val add element gt set gt set val member element gt set gt bool end WrongStringSet add gee WrongStringSet empty Characters 19 24 This expression has type string but is here used with type WrongStringSet element WrongSet OrderedString element The problem here is that SET specifies the type element abstractly so that the type equality between element in the result of the functor and t in its argument is forgotten Consequently WrongStringSet element is not the same type as string and the operations of WrongStringSet cannot be applied to strings As demonstrated above it is important that the type element in the signature SET be declared equal to Elt t unfortunately this is impossible above since SET is defined in a context where Elt does not exist To overcome this difficulty Objective Caml provides a with type construct over signatures that allows to enrich a signature with extra type equalities module AbstractSet Set functor Elt ORDERED_TYPE gt SET with type element Elt t module AbstractSet functor Elt ORDERED_TYPE gt sig type element Elt t and set val empty set val add element gt set gt set val member element gt set gt bool end Ch
19. SO_KEEPALIVE Keep connection active SO_DONTROUTE Bypass the standard routing algorithms SO_OOBINLINE Leave out of band data in line The socket options settable with setsockopt val getsockopt file_descr gt socket_option gt bool Return the current status of an option in the given socket val setsockopt file_descr gt socket_option gt bool gt unit Set or clear an option in the given socket High level network connection functions val open_connection sockaddr gt in_channel out_channel Connect to a server at the given address Return a pair of buffered channels connected to the server Remember to call flush on the output channel at the right times to ensure correct synchronization Chapter 18 The unix library Unix system calls 275 val shutdown_connection in_channel gt unit Shut down a connection established with open_connection that is transmit an end of file condition to the server reading on the other side of the connection val establish_server in_channel gt out_channel gt a gt sockaddr gt unit Establish a server on the given address The function given as first argument is called for each connection with two buffered channels connected to the client A new process is created for each connection The function establish_server never returns normally Host and protocol databases type host_entry h_name string h_aliases string array h_addr
20. class copy object a method copy a end Only the override can be used to actually override fields and only the 0o copy primitive can be used externally Cloning can also be used to provide facilities for saving and restoring the state of objects class backup object self mytype val mutable copy None method save copy lt Some lt copy None gt method restore match copy with Some x gt x None gt self end class backup object a val mutable copy a option method restore a method save unit end The above definition will only backup one level The backup facility can be added to any class using multiple inheritance class a backup_ref x object inherit a ref x inherit backup end class a backup_ref Chapter 2 Objects in Caml 43 2a gt object b val mutable copy b option val mutable x a method get a method restore b method save unit method set a gt unit end let rec get p n if n 0 then p get else get p restore n 1 val get lt get b restore a gt as a gt int gt b lt fun gt let p new backup_ref O in p save p set 1 p save p set 2 get p 0 get p 1 get p 2 get p 3 get p 4 int list 2 1 1 1 1 A variant of backup could retain all copies We then add a method clear to manually erase all copies class backup
21. client_view end struct class account x client_view object inherit B bank inherit check_client x end let discount x let c new account x in if today lt 1998 10 30 then c deposit m 100 c end HHH HHH HHH HH HH HH HH HHH HH HH HH HH HHH HH HH OH FH OH FF OF end This shows the use of modules to group several class definitions that can in fact be thought of as a single unit This unit would be provided by a bank for both internal and external uses This is implemented as a functor that abstracts over the currency so that the same code can be used to provide accounts in different currencies 62 The class bank is the real implementation of the bank account it could have been inlined This is the one that will be used for further extensions refinements etc Conversely the client will only be given the client view module Euro_account Account Euro module Client Euro_account Client Euro_account new Client account new Euro c 100 Hence the clients do not have direct access to the balance nor the history of their own accounts Their only way to change their balance is to deposit or withdraw money It is important to give the clients a class and not just the ability to create accounts such as the promotional discount account so that they can personalize their account For instance a client may refine the deposit and withdraw methods so as to do his own financial bookkeeping automa
22. expr Coercion The type of an object can be coerced weakened to a supertype The expression expr gt typexpr coerces the expression expr to type typexpr The expression expr typexpr gt typexprs coerces the expression expr from type typexpr to type typexprs The former operator will sometimes fail to coerce an expression expr from a type t to a type tg even if type t is a subtype of type t2 In this case the latter operator should be used In a class definition coercion to the type this class defines is the identity as this type abbrevi ation is not yet completely defined Object duplication An object can be duplicated using the library function Oo copy see section 17 17 Inside a method the expression lt inst var name expr inst var name expr gt returns a copy of self with the given instance variables replaced by the values of the associated expressions other instance variables have the same value in the returned object as in self 5 8 Type and exception definitions 5 8 1 Type definitions Type definitions bind type constructors to data types either variant types record types type abbreviations or abstract data types They also bind the value constructors and record labels associated with the definition type definition type typedef and typedef typedef type params typeconstr name type equation type representation type constra type equation typexpr type representa
23. gt gt point lt fun gt In this case the function colored_point_to_point is an instance of the function to_point This is not always true however The fully explicit coercion is more precise and is sometimes unavoidable Here is an example where the shorter form fails class virtual c object method virtual m c end class virtual c object method virtual m c end class c object self inherit c method m self gt c method m 1 end Characters 59 63 This expression cannot be coerced to type c lt m c gt it has type lt mic gt but is here used with type lt m a gt as a Type c lt m c gt is not compatible with type a Self type cannot be unified with a closed object type The type of the coercion to type c can be seen here function x gt x gt c lt m a gt as a gt c lt fun gt As class c inherits from class c its method m must have type c On the other hand in expression self gt c the type of self and the domain of the coercion above must be unified That is the type of the method m in self i e c is also the type of self So the type of self is c This is a contradiction as the type of self has a method m whereas type c does not The desired coercion of type lt m c gt gt c can be obtained by using a fully explicit coercion function x gt x c gt c c gt c lt fun gt
24. gt or are read as a single token from the infix symbol or prefix symbol class These symbols are parsed as prefix and infix operators inside expressions but otherwise behave much as identifiers 78 Keywords The identifiers below are reserved as keywords and cannot be employed otherwise and as assert asr begin class closed constraint do done downto else end exception external false for fun function functor if in include inherit land lazy let lor 1sl lsr lxor match method mod module mutable new of open or parser private rec sig struct then to true try type val virtual when while with The following character sequences are also keywords amp gt 7 i Ki ay 3 lt I lt lt I gt gt J Ambiguities Lexical ambiguities are resolved according to the longest match rule when a character sequence can be decomposed into two tokens in several different ways the decomposition retained is the one with the longest first token Line number directives linenum directive 4 0 9 0 9 string character Preprocessors that generate Caml source code can insert line number directives in their output so that error messages produced by the compiler contain line numbers and file names referring to the source file before preprocessing instead of after preprocessing A line number directive is composed of a sharp sign followed by a positive integer the sourc
25. object method bump unit method get_x int end fun x restricted_point_type gt x restricted_point_type gt restricted_point_type lt fun gt In addition to documentation these class interfaces can be used to constrain the type of a class Both instance variables and concrete private methods can be hidden by a class type constraint Public and virtual methods however cannot class restricted_point x restricted_point x restricted_point_type class restricted_point int gt restricted_point_type Or equivalently class restricted_point restricted_point int gt restricted_point_type class restricted_point int gt restricted_point_type The interface of a class can also be specified in a module signature and used to restrict the inferred signature of a module module type POINT sig class restricted_point int gt object method get_x int method bump unit end end module type POINT sig class restricted_point int gt object method bump unit method get_x int end end module Point POINT struct class restricted_point restricted_point end module Point POINT 2 7 Inheritance We illustrate inheritance by defining a class of colored points that inherits from the class of points This class has all instance variables and all methods of class point plus a new instance variable c and a new method color Chapter 2
26. val stdin in_channel val stdout out_channel val stderr out_channel The standard input standard output and standard error output for the process Output functions on standard output val print_char char gt unit Print a character on standard output val print_string string gt unit Print a string on standard output val print_int int gt unit Print an integer in decimal on standard output val print_float float gt unit Print a floating point number in decimal on standard output val print_endline string gt unit Print a string followed by a newline character on standard output val print_newline unit gt unit Print a newline character on standard output and flush standard output This can be used to simulate line buffering of standard output Chapter 16 The core library 203 Output functions on standard error val prerr_char char gt unit Print a character on standard error val prerr_string string gt unit Print a string on standard error val prerr_int int gt unit Print an integer in decimal on standard error val prerr_float float gt unit Print a floating point number in decimal on standard error val prerr_endline string gt unit Print a string followed by a newline character on standard error and flush standard error val prerr_newline unit gt unit Print a newline character on standard error and flush standard error Input functions on standard in
27. 203 readdir 266 readlink 267 really_input 206 receive 297 recv 274 300 recvfrom 274 300 red 303 ref 207 regexp 287 regexp_case_fold 288 regexp_string 288 regexp_string_case_fold 288 register 216 register_exception 216 remove 231 253 310 remove_assoc 238 remove_assq 238 rename 254 264 replace 310 replace_first 289 replace_matched 290 reset 215 rev 235 rev_append 235 rev_map 236 rev_map2 236 rewinddir 266 rgb 303 rhs_end 242 rhs_start 242 rindex 252 rindex_from 252 rmdir 265 round_num 282 search_backward 288 search_forward 288 seek_in 207 seek_out 205 322 select 267 295 298 299 self 294 self_init 245 send 274 297 300 sendto 274 300 set 212 229 251 256 Set module 246 set_all_formatter_output_functions 223 set_approx_printing 285 set_binary_mode_in 207 set_binary_mode_out 205 set_close_on_exec 265 set_color 303 set_ellipsis_text 223 set_error_when_null_denominator 284 set_floating_precision 285 set_font 305 set_formatter_out_channel 223 set_formatter_output_functions 223 set_line_width 304 set_margin 221 set_max_boxes 221 set_max_indent 221 set_nonblock 265 set_normalize_ratio 284 set_normalize_ratio_when_printing 285 set_signal 255 set_tab 222 set_text_size 305 setgid 271 setitimer 270 setsid 278 setsockopt 274 setuid 271 shutdown 273 shutdown_connection 275 sigabrt
28. 255 sigalrm 255 sigchld 255 sigcont 255 sigfpe 255 sighup 255 sigill 255 sigint 255 sigkill 255 sign_num 283 signal 255 297 sigpending 268 sigpipe 255 sigprocmask 268 sigprof 255 sigquit 255 sigsegv 255 sigstop 255 sigsuspend 268 sigterm 255 sigtstp 255 sigttin 255 sigttou 255 sigusri 255 sigusr2 255 sigvtalrm 255 sin 199 sinh 200 size_x 303 size_y 303 sleep 270 299 snd 202 socket 273 300 socketpair 273 300 Sort module 248 sound 308 split 238 290 split_delim 290 sprintf 227 244 sqrt 199 square_num 282 Stack module 248 Stack_overflow exception 195 stat 229 264 std_formatter 224 stdbuf 224 stderr 202 261 stdin 202 261 stdout 202 261 Str module 287 str_formatter 224 Stream module 249 string 217 INDEX TO THE LIBRARY String module 251 string_after 291 string_before 290 string_match 288 string_of_bool 201 string_of_float 201 string_of_inet_addr 272 string_of_int 201 string_of_num 284 string_partial_match 288 sub 213 252 sub_num 282 substitute_first 290 substring 217 succ 197 succ_num 283 symbol_end 242 symbol_start 242 symlink 267 sync 298 Sys module 253 Sys_blocked_io exception 195 Sys_error exception 195 system 261 299 take 245 tan 199 tanh 200 tcdrain 277 tcflow 278 tcflush 277 tcgetattr 277 tcsendbreak 277 tcsetattr 277 temp_file 218 text_size 305
29. 282 Mutex module 296 nat_of_num 284 new_channel 297 next 250 nextkey 310 nice 261 not 197 Not_found exception 195 npeek 251 nth 235 Num module 281 num_of_big_int 284 num_of_int 284 320 num_of_nat 284 num_of_ratio 284 num_of_string 284 of_channel 250 of _list 214 250 of_string 250 Oo module 242 open_box 219 open_connection 274 300 open_graph 302 open_hbox 222 open_hovbox 222 open_hvbox 222 open_in 206 open_in_bin 206 open_in_gen 206 open_out 204 open_out_bin 204 open_out_gen 204 open_process 267 299 open_process_full 267 open_process_in 267 open_process_out 267 299 open_tbox 222 open_vbox 222 opendbm 310 opendir 266 openfile 262 or operator 197 OrderedType module type 239 246 os_type 254 out_channel_length 205 out_channel_of_descr 262 Out_of_memory exception 195 output 205 217 output_binary_int 205 output_buffer 215 output_byte 205 output_char 204 output_string 205 output_value 205 over_max_boxes 221 parse 211 Parse_error exception 243 Parsing module 242 partition 237 pause 268 peek 245 251 Pervasives module 193 pipe 266 299 plot 304 point_color 304 poll 298 pop 249 pos_in 207 pos_out 205 power_num 282 pp_close_box 226 pp_close_tbox 226 pp_force_newline 226 pp_get_all_formatter_output_functions 226 pp_get_ellipsis_text 226 pp_get_formatter_output_functions 226 pp_get_mar
30. For the bytecode compiler argv 0 and argv 1 are also consulted to find the file containing the bytecode e The call to caml_main initializes the Caml runtime system loads the bytecode in the case of the bytecode compiler and executes the initialization code of the Caml program Typically this initialization code registers callback functions using Callback register Once the Caml initialization code is complete control returns to the C code that called caml_main e The C code can then invoke Caml functions using the callback mechanism see section 15 6 1 15 6 5 Embedding the Caml code in the C code The bytecode compiler in custom runtime mode ocamlc custom normally appends the bytecode to the executable file containing the custom runtime This has two consequences First the final linking step must be performed by ocamlc Second the Caml runtime library must be able to find the name of the executable file from the command line arguments When using caml_main argv as in section 15 6 4 this means that argv 0 or argv 1 must contain the executable file name An alternative is to embed the bytecode in the C code The output obj option to ocamlc is provided for this purpose It causes the ocamlc compiler to output a C object file o file containing the bytecode for the Caml part of the program as well as a caml_startup function The C object file produced by ocamlc output obj can then be linked with C code using the standard C co
31. Thus one can define class c as follows class c object self inherit c method m self c gt c method m 1 end class c object method m c method m int end Chapter 2 Objects in Caml 39 An alternative is to define class c this way of course this definition is not equivalent to the previous one class virtual c object _ a method virtual m a end class virtual c object a method virtual m a end Then a coercion operator is not even required class c object self inherit c method m self method m 1 end class c object a method m a method m int end Here the simple coercion operator e gt c can be used to coerce an object expression e from type c to type c Semi implicit coercions are actually defined so as to work correctly with classes returning self mew c gt c c lt obj gt Another common problem may occur when one tries to define a coercion to a class c inside the definition of class c The problem is due to the type abbreviation not being completely defined yet and so its subtypes are not clearly known Then a coercion _ c gt c is taken to be the identity function as in function x gt x gt a a gt a lt fun gt As a consequence if the coercion is applied to self as in the following example the type of self is unified with the closed type c a close
32. along with a number of other list and array functionals is predefined because it is often useful but there is nothing magic with it it can easily be defined as follows let rec map f 1 match 1 with gt O hd tl gt f hd map f tl val map a gt b gt a list gt b list lt fun gt 1 4 Records and variants User defined data structures include records and variants Both are defined with the type declara tion Here we declare a record type to represent rational numbers type ratio num int denum int type ratio num int denum int let add_ratio ri r2 num ri num r2 denum r2 num ri denum denum ri denum r2 denum val add_ratio ratio gt ratio gt ratio lt fun gt add_ratio num 1 denum 3 num 2 denum 5 ratio num 11 denum 15 The declaration of a variant type lists all possible shapes for values of that type Each case is identified by a name called a constructor which serves both for constructing values of the variant type and inspecting them by pattern matching Constructor names are capitalized to distinguish them from variable names which must start with a lowercase letter For instance here is a variant type for doing mixed arithmetic integers and floats type number Int of int Float of float Error type number Int of int Float of float Error This declaration expresses that a value of typ
33. amp Field r 1 tail cdr of the result tail return rT It would be incorrect to perform Field r 1 tail directly because the allocation of tail has taken place since r was allocated tail is not registered as a root because there is no allocation between the assignment where it takes its value and the modify statement that uses the value 15 6 Callbacks from C to Caml So far we have described how to call C functions from Caml In this section we show how C functions can call Caml functions either as callbacks Caml calls C which calls Caml or because the main program is written in C Chapter 15 Interfacing C with Objective Caml 183 15 6 1 Applying Caml closures from C C functions can apply Caml functional values closures to Caml values The following functions are provided to perform the applications e callback f a applies the functional value f to the value a and return the value returned by f e callback2 f a b applies the functional value f which is assumed to be a curried Caml function with two arguments to a and b e callback3 f a b c applies the functional value f a curried Caml function with three arguments to a b and c e callbackN f n args applies the functional value fto the n arguments contained in the array of values args If the function f does not return but raises an exception that escapes the scope of the application then this exception is propagated to the next e
34. cells If it displays few Growing heap messages but with a huge increment in the heap size this is probably an attempt to build an excessively large array or string 134 Chapter 10 Native code compilation ocamlopt This chapter describes the Objective Caml high performance native code compiler ocamlopt which compiles Caml source files to native code object files and link these object files to produce standalone executables The native code compiler is only available on certain platforms It produces code that runs faster than the bytecode produced by ocamlc at the cost of increased compilation time and executable code size Compatibility with the bytecode compiler is extremely high the same source code should run identically when compiled with ocamlc and ocamlopt It is not possible to mix native code object files produced by ocamlc with bytecode object files produced by ocamlopt a program must be compiled entirely with ocamlopt or entirely with ocamlc Native code object files produced by ocamlopt cannot be loaded in the toplevel system ocaml 10 1 Overview of the compiler The ocamlopt command has a command line interface very close to that of ocamlc It accepts the same types of arguments e Arguments ending in mli are taken to be source files for compilation unit interfaces In terfaces specify the names exported by compilation units they declare value names with their types define public data types declare abstr
35. end 4 2 Simple modules as classes One may wonder whether it is possible to treat primitive types such as integers and strings as objects Although this is usually uninteresting for integers or strings there may be some situations where this is desirable The class money above is such an example We show here how to do it for strings 4 2 1 Strings A naive definition of strings as objects could be class ostring s object method get n String get n method set n c String set nc method print print_string s method copy new ostring String copy s end class ostring string gt object method copy ostring method get string gt int gt char method print unit 64 method set string gt int gt char gt unit end However the method copy returns an object of the class string and not an objet of the current class Hence if the class is further extended the method copy will only return an object of the parent class class sub_string s object inherit ostring s method sub start len new sub_string String sub s start len end class sub_string string gt object method copy ostring method get string gt int gt char method print unit method set string gt int gt char gt unit method sub int gt int gt sub_string end As seen in section 2 14 the solution is to use functional update instead We need to create an instance variable cont
36. et bsp ere Sieh Pie Bee Se Be i ee Spink es Se SD Patterns 34S tu Be dera ae Be Parga See eae Hee ere Bh ee eA eek ee ards EA EXPLESSIONS si hier Bice See oh Bleek Male ek ee BP eA iy dad Gk els Type and exception definitions oeoo a e ee CASSOSY tig a 2 p he OAR a Shree Rk eC hee ee SO all Module types module specifications 2 a a Module expressions module implementations o ooo Compilation Units se so ecne aa 5 a a a a e Re a a E a a a 6 Language extensions 6 1 6 2 6 3 6 4 6 5 6 6 Streams and stream parsers oouo a Range patterns sos etet cats ee a ee Aa a ee ee a Assertion checking 0 a Deferred computations oaoa ee Record copy with update 2 ee Local mod le rie fy g 8 ect Bac a OE ee ee eae Sees II The Objective Caml tools 7 Batch compilation ocamlc 7 1 Overview of the compiler aooaa ee T2 OPUONS se oot Bee a Ate aoe eas Ae le ele eld aiaa Bache 7 3 Modules and the filesystem 2 2 2 0 2 ee A Common errors 2 02 206 Sate isle ee Re Ae et a et ce 8 The toplevel system ocaml Sale Options eke hak ed gs Dee Bae Bok ee GW aed ee Ree AK Ba es Se 8 2 Fopleveldir ctivesia a liga sok wo eal ee ie ae oe ee ead BG 8 3 The toplevel and the module system 0200000 e eee eee 8 4 CommMonerrors en hn ke Re te BU ee ee bo nt 8 5 Building custom toplevel systems ocamlmktop 2 0 4 S6 Options lt sce ake See we ee ba eee ede Pee
37. have a special unboxed more efficient representation These arrays are represented by pointers to blocks with tag Double_array_tag They should be accessed with the Double_field and Store_double_field macros 15 3 4 Concrete types Constructed terms are represented either by unboxed integers for constant constructors or by blocks whose tag encode the constructor for non constant constructors The constant constructors and the non constant constructors for a given concrete type are numbered separately starting from 0 in the order in which they appear in the concrete type declaration Constant constructors are represented by unboxed integers equal to the constructor number Non constant constructors declared with a n tuple as argument are represented by a block of size n tagged with the constructor number the n fields contain the components of its tuple argument Other non constant constructors are represented by a block of size 1 tagged with the constructor number the field 0 contains the value of the constructor argument Example Constructed term Representation O Val_int 0 false Val_int 0 true Val_int 1 Val_int 0 h t Block with size 2 and tag 0 first field con tains h second field t As a convenience caml mlvalues h defines the macros Val_unit Val_false and Val_true to refer to false and true 15 3 5 Objects Objects are represented as zero tagged blocks The first field of the bl
38. matching is resumed against the patterns following pattern Local definitions The let and let rec constructs bind value names locally The construct let pattern expr and and pattern expr in expr evaluates expr expr in some unspecified order then matches their values against the patterns pattern pattern If the matchings succeed expr is evaluated in the environment enriched by the bindings performed during matching and the value of expr is returned as the value of the whole let expression If one of the matchings fails the exception Match_failure is raised An alternate syntax is provided to bind variables to functional values instead of writing let ident fun pattern pattern gt expr in a let expression one may instead write let ident pattern pattern expr Recursive definitions of names are introduced by let rec let rec pattern expr and and pattern expr in expr The only difference with the let construct described above is that the bindings of names to values performed by the pattern matching are considered already performed when the expressions expr to expr are evaluated That is the expressions expr to expr can reference identifiers that are bound by one of the patterns pattern pattern and expect them to have the same value as in expr the body of the let rec construct The recursive definition is guaranteed to behave as described above if the expressions expr to exp
39. module module name module type module expr instead of module module name module expr module type Another derived form is module module name name module type namen module type module expr which is equivalent to module module name functor name module type gt gt module expr Module type definitions A definition for a module type is written module type modtype name module type It binds the name modtype name to the module type denoted by the expression module type Chapter 5 The Objective Caml language 109 Opening a module path The expression open module path in a structure does not define any components nor perform any bindings It simply affects the parsing of the following items of the structure allowing components of the module denoted by module path to be referred to by their simple names name instead of path accesses module path name The scope of the open stops at the end of the structure expression 5 11 3 Functors Functor definition The expression functor module name module type gt module expr evaluates to a functor that takes as argument modules of the type module type binds module name to these modules evaluates module expr in the extended environment and returns the resulting modules as results No restrictions are placed on the type of the functor argument in particular a functor may take another functor as argument higher order functor Functor a
40. mutable lex_last_action int mutable lex_eof_reached bool 234 The type of lexer buffers A lexer buffer is the argument passed to the scanning functions defined by the generated scanners The lexer buffer holds the current state of the scanner plus a function to refill the buffer from the input val from_channel in_channel gt lexbuf Create a lexer buffer on the given input channel Lexing from_channel inchan returns a lexer buffer which reads from the input channel inchan at the current reading position val from_string string gt lexbuf Create a lexer buffer which reads from the given string Reading starts from the first character in the string An end of input condition is generated when the end of the string is reached val from_function string gt int gt int gt lexbuf Create a lexer buffer with the given function as its reading method When the scanner needs more characters it will call the given function giving it a character string s and a character count n The function should put n characters or less in s starting at character number 0 and return the number of characters provided A return value of 0 means end of input Functions for lexer semantic actions The following functions can be called from the semantic actions of lexer definitions the ML code enclosed in braces that computes the value returned by lexing functions They give access to the character string matched by the regular expr
41. outside of the heap It is incorrect to try and allocate a zero sized block using the functions below For instance Atom 0 represents the empty array alloc n t returns a fresh block of size n with tag t If tis less than No_scan_tag then the fields of the block are initialized with a valid value in order to satisfy the GC constraints alloc_tuple n returns a fresh block of size n words with tag 0 alloc_string n returns a string value of length n characters The string initially contains garbage copy_string s returns a string value containing a copy of the null terminated C string s a char copy_double d returns a floating point value initialized with the double d alloc_array f a allocates an array of values calling function f over each element of the input array a to transform it into a value The array a is an array of pointers terminated by the null pointer The function f receives each pointer as argument and returns a value The zero tagged block returned by alloc_array f a is filled with the values returned by the successive calls to f This function must not be used to build an array of floating point numbers copy_string_array p allocates an array of strings copied from the pointer to a string array p a char Low level interface The following functions are slightly more efficient than alloc but also much more difficult to use From the standpoint of the allocation functions blocks are divided a
42. side effects Value definitions A value definition let rec let binding and let binding bind value names in the same way as a let in expression see section 5 7 1 The value names appearing in the left hand sides of the bindings are bound to the corresponding values in the right hand sides 108 A value definition external value name typexpr external declaration implements value name as the external function specified in external declaration see chapter 15 Type definitions A definition of one or several type components is written type typedef and typedef and consists of a sequence of mutually recursive definitions of type names Exception definitions Exceptions are defined with the syntax exception constr decl Class definitions A definition of one or several classes is written class class binding and class binding and consists of a sequence of mutually recursive definitions of class names Class definitions are described more precisely in section 5 9 3 Class type definitions A definition of one or several classes is written class type classtype def and classtype def and consists of a sequence of mutually recursive definitions of class type names Class type definitions are described more precisely in section 5 9 5 Module definitions The basic form for defining a module component is module module name module expr which evaluates module expr and binds the result to the name module name One can write
43. string gt string Return a copy of the argument with the first letter set to uppercase uncapitalize string gt string Return a copy of the argument with the first letter set to lowercase 17 28 Module Sys system interface val val val argv string array The command line arguments given to the process The first element is the command name used to invoke the program The following elements are the command line arguments given to the program file_exists string gt bool Test if a file with the given name exists remove string gt unit Remove the given file name from the file system 254 val val val val val val val val val val val rename string gt string gt unit Rename a file The first argument is the old name and the second is the new name getenv string gt string Return the value associated to a variable in the process environment Raise Not_found if the variable is unbound command string gt int Execute the given shell command and return its exit code time unit gt float Return the processor time in seconds used by the program since the beginning of execution chdir string gt unit Change the current working directory of the process getcwd unit gt string Return the current working directory of the process interactive bool ref This reference is initially set to false in standalone programs and to true if the code is being executed
44. t gt a gt b Hashtbl find tbl x returns the current binding of x in tbl or raises Not_found if no such binding exists find_all a b t gt a gt b list Hashtbl find_all tbl x returns the list of all data associated with x in tbl The current binding is returned first then the previous bindings in reverse order of introduction in the table mem a b t gt a gt bool Hashtbl mem tbl x checks if x is bound in tbl remove a b t gt a gt unit Hashtbl remove tbl x removes the current binding of x in tbl restoring the previous binding if it exists It does nothing if x is not bound in tbl iter a gt b gt unit gt a b t gt unit Hashtbl iter f tbl applies f to all bindings in table tbl f receives the key as first argument and the associated value as second argument The order in which the bindings are passed to f is unspecified Each binding is presented exactly once to f 232 Functorial interface module type HashedType sig type t val equal t gt t gt bool val hash t gt int end The input signature of the functor Hashtbl Make t is the type of keys equal is the equality predicate used to compare keys hash is a hashing function on keys returning a non negative integer It must be such that if two keys are equal according to equal then they must have identical hash values as computed by hash Examples suitable equal hash pai
45. table self hash key add key end class a b hashtbl int gt a b hash_table H H HH H H 68 4 2 3 Sets Implementing sets leads to another difficulty Indeed the method union needs to be able to access the internal representation of another object of the same class This is another instance of friend functions as seen in section 2 15 Indeed this is the same mechanism used in the module Set in the absence of objects In the object oriented version of sets we only need to add an additional method tag to return the representation of a set Since sets are parametric in the type of elements the method tag has a parametric type a tag concrete within the module definition but abstract in its signature From outside it will then be guaranteed that two objects with a method tag of the same type will share the same representation module type SET sig type a tag class a c object b method is_empty bool method mem a gt bool method add a gt b method union b gt b method iter a gt unit gt unit method tag a tag end end module Set SET struct let rec merge 11 12 match 11 with gt 12 ht t1 gt match 12 with gt 11 h2 t2 gt if hi lt h2 then hi merge t1 12 else if hi gt h2 then h2 merge 11 t2 else merge t1 12 type a tag a list class a c object _ b val repr a
46. v1 Vn such that pattern matches v fori 1 n Record patterns The pattern label pattern label pattern matches records that define at least the labels label through label and such that the value associated to label match the pattern pattern for i 1 n The record value can define more labels than label labeln the values associated to these extra labels are not taken into account for matching Chapter 5 The Objective Caml language 87 5 7 Expressions expr pattern matching multiple matching let binding infix op value path constant expr begin expr end expr typexpr expr expr expr neconstr expr expr expr expr expr I expr expr label expr label expr expr expr prefix symbol expr expr infix op expr expr label expr label lt expr expr expr expr expr lt expr expr expr expr expr lt expr if expr then expr else expr while expr do expr done for ident expr to downto expr do expr done expr expr match expr with pattern matching function pattern matching fun multiple matching try expr with pattern matching let rec let binding and let binding in expr new class path expr method name expr gt typexpr expr typexpr gt typexpr lt inst var name expr inst var name expr gt pattern when expr gt expr pattern when expr gt expr
47. value name constant pattern as value name pattern pattern typexpr pattern pattern neconstr pattern pattern pattern label pattern label pattern pattern pattern pattern pattern The table below shows the relative precedences and associativity of operators and non closed pattern constructions The constructions with higher precedences come first Operator Associativity Constructor application me right left as Patterns are templates that allow selecting data structures of a given shape and binding iden tifiers to components of the data structure This selection operation is called pattern matching its outcome is either this value does not match this pattern or this value matches this pattern resulting in the following bindings of names to values Variable patterns A pattern that consists in a value name matches any value binding the name to the value The pattern _ also matches any value but does not bind any name Patterns are linear a variable cannot appear several times in a given pattern In particular there is no way to test for equality between two parts of a data structure using only a pattern but when guards can be used for this purpose 86 Constant patterns A pattern consisting in a constant matches the values that are equal to this constant Alias patterns The pattern pattern as value name matches the same values as
48. 0 9 A Fla 7 i 00 0 7 Ob 0B 0 1 An integer literal is a sequence of one or more digits optionally preceded by a minus sign By default integer literals are in decimal radix 10 The following prefixes select a different radix Prefix Radix Ox OX hexadecimal radix 16 Oo 00 octal radix 8 Ob OB binary radix 2 The initial O is the digit zero the O for octal is the letter O The interpretation of integer literals that fall outside the range of representable integer values is undefined Floating point literals float literal 0 9 7 0 9 e E 0 9 7 Floating point decimals consist in an integer part a decimal part and an exponent part The integer part is a sequence of one or more digits optionally preceded by a minus sign The decimal part is a decimal point followed by zero one or more digits The exponent part is the character e or E followed by an optional or sign followed by one or more digits The decimal part or the exponent part can be omitted but not both to avoid ambiguity with integer literals The interpretation of floating point literals that fall outside the range of representable floating point values is undefined Character literals regular char NGP alt b r gt 0 9 0 9 0 9 char literal Chapter 5 The Objective Caml language 77 Character literals are delimited by single
49. 11 2 3 Entry points The names of the entry points must be valid identifiers for Caml values starting with a lowercase letter 11 2 4 Regular expressions The regular expressions are in the style of lex with a more Caml like syntax gt char A character constant with the same syntax as Objective Caml character constants Match the denoted character Underscore Match any character eof Match the end of the lexer input Note On some systems with interactive input and end of file may be followed by more characters However ocamllex will not correctly handle regular expressions that contain eof followed by something else Chapter 11 Lexer and parser generators ocamllex ocamlyacc 143 string A string constant with the same syntax as Objective Caml string constants Match the corresponding sequence of characters character set Match any single character belonging to the given character set Valid character sets are single character constants c ranges of characters c1 c2 all characters between c and c2 inclusive and the union of two or more character sets denoted by concatenation character set Match any single character not belonging to the given character set regexp Repetition Match the concatenation of zero or more strings that match regexp regexp Strict repetition Match the concatenation of one or more strings that match regexp regexp Option Match eit
50. Objects in Caml 33 class colored_point x c string object inherit point x val c c method color c end class colored_point int gt string gt object val c string val mutable x int method color string method get_offset int method get_x int method move int gt unit end let p new colored_point 5 red val p colored_point lt obj gt p get_x p color int string 5 red A point and a colored point have incompatible types since a point has no method color However the function get_x below is a generic function applying method get_x to any object p that has this method and possibly some others which are represented by an ellipsis in the type Thus it applies to both points and colored points let get_succ_x p p get_x 1 val get_succ_x lt get_x int gt gt int lt fun gt get_succ_x p get_succ_x p int 8 Methods need not be declared previously as shown by the example let set_x p p set_x val set_x lt set_x a gt gt a lt fun gt let incr p set_x p get_succ_x p val incr lt get_x int set_x int gt a gt gt a lt fun gt 2 8 Multiple inheritance Multiple inheritance is allowed Only the last definition of a method is kept the redefinition in a subclass of a method that was visible in the parent class overrides the definition in the parent class Prev
51. Operations on data structures Products The expression expr expr evaluates to the n tuple of the values of expressions expr to expr The evaluation order for the subexpressions is not specified Variants The expression ncconstr expr evaluates to the variant value whose constructor is ncconstr and whose argument is the value of expr For lists some syntactic sugar is provided The expression expr exprs stands for the con structor applied to the argument expr expr and therefore evaluates to the list whose head is the value of expr and whose tail is the value of expr The expression expr expr is equivalent to expr expr and therefore evaluates to the list whose elements are the values of expr to expr Chapter 5 The Objective Caml language 93 Records The expression label expr label expr evaluates to the record value label v 3 label vn where v is the value of expr for i 1 n The labels label to label must all belong to the same record types all labels belonging to this record type must appear exactly once in the record expression though they can appear in any order The order in which expr to expr are evaluated is not specified The expression expr label evaluates expr to a record value and returns the value associated to label in this record value The expression expr label lt expr evaluates expr to a record value whic
52. Run the program until a breakpoint is hit or the program terminates step 0 Load the program and stop on the first event goto time Load the program and execute it until the given time Useful when you already know ap proximately at what time the problem appears Also useful to set breakpoints on function values that have not been computed at time 0 see section 13 5 The execution of a program is affected by certain information it receives when the debugger starts it such as the command line arguments to the program and its working directory The debugger provides commands to specify this information set arguments and cd These com mands must be used before program execution starts If you try to change the arguments or the working directory after starting your program the debugger will kill the program after asking for confirmation 13 4 3 Running the program The following commands execute the program forward or backward starting at the current time The execution will stop either when specified by the command or when a breakpoint is encountered run Execute the program forward from current time Stops at next breakpoint or when the program terminates reverse Execute the program backward from current time Mostly useful to go to the last breakpoint encountered before the current time Chapter 13 The debugger ocamldebug 157 step count Run the program and stop at the next event With an argument do it count times
53. The argument expr is not evaluated at this point in the program Instead its evaluation will be performed the first time Lazy force is applied to the value v returning the actual value of expr Subsequent applications of Lazy force to v do not evaluate expr again The expression lazy expr is equivalent to ref Lazy Delayed fun gt expr For more information see the description of module Lazy in the standard library section 17 12 6 5 Record copy with update The expression expr with Ibl expr Ibl expr builds a fresh record with fields Ibl 1bl equal to expr expr and all other fields having the same value as in the record expr In other terms it returns a shallow copy of the record expr except for the fields Ib Iblp which are initialized to expr expr For example type point x float y float z float let proj p p with x 0 0 let proj p x 0 0 y p y z p z The two definitions of proj above are equivalent 6 6 Local modules The expression let module module name module expr in expr locally binds the module expres sion module expr to the identifier module name during the evaluation of the expression expr It then returns the value of expr For example let remove_duplicates comparison_fun string_list let module StringSet Set Make struct type t string let compare comparison_fun end in StringSet elements List fold_right StringSet add string_list Stri
54. addition to the compiled object code file z cmo The file x cmi produced corresponds to an interface that exports everything that is defined in the implementation z m1 e Arguments ending in cmo are taken to be compiled object bytecode These files are linked together along with the object files obtained by compiling m1 arguments if any and the Caml Light standard library to produce a standalone executable program The order in which cmo and ml arguments are presented on the command line is relevant compilation units are initialized in that order at run time and it is a link time error to use a component of a unit before having initialized it Hence a given x cmo file must come before all cmo files that refer to the unit z 117 118 e Arguments ending in cma are taken to be libraries of object bytecode A library of object bytecode packs in a single file a set of object bytecode files cmo files Libraries are built with ocamlc a see the description of the a option below The object files contained in the library are linked as regular cmo files see above in the order specified when the cma file was built The only difference is that if an object file contained in a library is not referenced anywhere in the program then it is not linked in e Arguments ending in c are passed to the C compiler which generates a o object file This object file is linked with the program if the custom flag is set see the description of
55. also the set arguments command The following command line options are recognized I directory Add directory to the list of directories searched for source files and compiled files See also the directory command 153 154 s socket Use socket for communicating with the debugged program See the description of the com mand set socket section 13 8 6 for the format of socket c count Set the maximum number of simultaneously live checkpoints to count cd directory Run the debugger program from the working directory directory instead of the current di rectory See also the cd command emacs Tell the debugger it is executed under Emacs See section 13 10 for information on how to run the debugger under Emacs 13 2 2 Exiting the debugger The command quit exits the debugger You can also exit the debugger by typing an end of file character usually ctr1 D Typing an interrupt character usually ctr1 C will not exit the debugger but will terminate the action of any debugger command that is in progress and return to the debugger command level 13 3 Commands A debugger command is a single line of input It starts with a command name which is followed by arguments depending on this name Examples run goto 1000 set arguments arg1 arg2 A command name can be truncated as long as there is no ambiguity For instance go 1000 is understood as goto 1000 since there are no other commands whose name starts with go Fo
56. are used to give names to several classes of language objects and refer to these objects by name later e value names syntactic class value name e value constructors constant class cconstr name or non constant class ncconstr name e type constructors typeconstr name e record labels label name e class names class name e method names method name e instance variable names inst var name e module names module name e module type names modtype name These nine name spaces are distinguished both by the context and by the capitalization of the identifier whether the first letter of the identifier is in lowercase written lowercase ident below or in uppercase written capitalized ident Underscore is considered a lowercase letter for this purpose Chapter 5 The Objective Caml language 81 Naming objects value name operator name cconstr name ncconstr name typeconstr name label name module name modtype name class name inst var name method name lowercase ident operator name prefix symbol infix symbol or amp capitalized ident false true capitalized ident lowercase ident lowercase ident capitalized ident ident lowercase ident lowercase ident lowercase ident As shown above prefix and infix symbols as well as some keywords can be used as value names Dis i provided they are written between parentheses Keywords such as
57. backstep count Run the program backward and stop at the previous event With an argument do it count times next count Run the program and stop at the next event skipping over function calls With an argument do it count times previous count Run the program backward and stop at the previous event skipping over function calls With an argument do it count times finish Run the program until the current function returns start Run the program backward and stop at the first event before the current function invocation 13 4 4 Time travel You can jump directly to a given time without stopping on breakpoints using the goto command As you move through the program the debugger maintains an history of the successive times you stop at The last command can be used to revisit these times each last command moves one step back through the history That is useful mainly to undo commands such as step and next goto time Jump to the given time last count Go back to the latest time recorded in the execution history With an argument do it count times set history size Set the size of the execution history 13 4 5 Killing the program kill Kill the program being executed This command is mainly useful if you wish to recompile the program without leaving the debugger 13 5 Breakpoints A breakpoint causes the program to stop whenever a certain point in the program is reached It can be set in several ways using the br
58. be extended by inheritance For in stance one may enrich the subject with new behaviors and refined the behavior of the observer class observer richer_window_subject object self inherit observer window_subject val mutable size 1 method resize x size lt size x self notify_observers Resize val mutable top false method raise top lt true self notify_observers Raise method draw Printf printf Position d Size 4d n position size end class a richer_window_subject object b constraint a lt notify b gt event gt unit gt val mutable observers a list val mutable position int val mutable size int val mutable top bool method add_observer a gt unit method draw unit method identity int method move int gt unit method notify_observers event gt unit method raise unit method resize int gt unit end class subject richer_window_observer object inherit subject window_observer as super method notify s e if e lt gt Raise then s raise super notify s e end class a richer_window_observer object constraint a lt draw unit raise unit gt method notify a gt event gt unit end We can also create a different kind of observer 72 class subject trace_observer object inherit subject event observer method notify s e Printf
59. byte representation of a marshaled value into a string buffer the program needs to read first Marshal header_size characters into the buffer then determine the length of the remainder of the representation using Marshal data_size make sure the buffer is large enough to hold the remaining data then read it and finally call Marshal from_string to unmarshal the value 17 17 Module Oo object oriented extension val copy lt gt as a gt a Oo copy o returns a copy of object o that is a fresh object with the same methods and instance variables as o 17 18 Module Parsing the run time library for parsers generated by ocamlyacc val symbol_start unit gt int val symbol_end unit gt int symbol_start and symbol_end are to be called in the action part of a grammar rule only They return the position of the string that matches the left hand side of the rule symbol_start returns the position of the first character symbol_end returns the position of the last character plus one The first character in a file is at position 0 val rhs_start int gt int val rhs_end int gt int Same as symbol_start and symbol_end but return the position of the string matching the nth item on the right hand side of the rule where n is the integer parameter to lhs_start and lhs_end n is 1 for the leftmost item Chapter 17 The standard library 243 val clear_parser unit gt unit Empty the parser stack Call it just afte
60. class synchronous communication 21 5 Module ThreadUnix thread compatible system calls 22 The graphics library 22 1 Module Graphics machine independent graphics primitives 23 The dbm library access to NDBM databases 23 1 Module Dbm interface to the NDBM databases 0 00 24 The dynlink library dynamic loading and linking of object files 24 1 Module Dynlink dynamic loading of bytecode object files V Appendix Index to the library Index of keywords 281 281 284 287 287 293 294 296 296 297 298 301 302 309 309 311 311 Foreword This manual documents the release 2 04 of the Objective Caml system It is organized as follows e Part I An introduction to Objective Caml gives an overview of the language e Part II The Objective Caml language is the reference description of the language e Part III The Objective Caml tools documents the compilers toplevel system and pro gramming utilities e Part IV The Objective Caml library describes the modules provided in the standard library e Part V Appendix contains an index of all identifiers defined in the standard library and an index of keywords Conventions Objective Caml runs on several operating systems The parts of this manual that are specific to one operating system are presented as shown below Unix This is material specif
61. colored_point gt point val colored_point_to_point colored_point gt point lt fun gt let p new point 3 and q new colored_point 4 blue val p point lt obj gt val q colored_point lt obj gt let 1 p colored_point_to_point q val 1 point list lt obj gt lt obj gt An object of type t can be seen as an object of type t only if t is a subtype of t For instance a point cannot be seen as a colored point p point gt colored_point Characters 0 28 Type point lt get_offset int get_x int move int gt unit gt is not a subtype of type colored_point lt color string get_offset int get_x int move int gt unit gt Indeed backward coercions are unsafe and should be combined with a type case possibly raising a runtime error However there is no such operation available in the language Be aware that subtyping and inheritance are not related Inheritance is a syntactic relation between classes while subtyping is a semantic relation between types For instance the class of 38 colored points could have been defined directly without inheriting from the class of points the type of colored points would remain unchanged and thus still be a subtype of points The domain of a coercion can usually be omitted For instance one can define let to_point cp cp gt point val to_point lt get_offset int get_x int move int gt unit
62. construct and unqualified names see section 5 3 However before referencing another compilation unit an implementation of that unit must be present in memory At start up the toplevel system contains implementations for all the modules in the the standard library Implementations for user modules can be entered with the load directive described above Referencing a unit for which no implementation has been provided results in the error Reference to undefined global Note that entering open mod merely accesses the compiled interface cmi file for mod but does not load the implementation of mod and does not cause any error if no implementation of mod has been loaded The error reference to undefined global mod will occur only when executing a value or module definition that refers to mod 8 4 Common errors This section describes and explains the most frequently encountered error messages Cannot find file filename The named file could not be found in the current directory nor in the directories of the search path If filename has the format mod cmi this means you have referenced the compilation unit mod but its compiled interface could not be found Fix compile mod mli or mod m1 first to create the compiled interface mod cmi If filename has the format mod cmo this means you are trying to load with load a bytecode object file that does not exist yet Fix compile mod m1 first If your program spans several
63. counters are returned in a stat record The fields of this record are minor_words Number of words allocated in the minor heap since the program was started promoted_words Number of words allocated in the minor heap that survived a minor collection and were moved to the major heap since the program was started major_words Number of words allocated in the major heap including the promoted words since the program was started minor_collections Number of minor collections since the program was started major_collections Number of major collection cycles not counting the current cycle since the program was started 228 heap_words Total number of words in the major heap heap_chunks Number of times the major heap size was increased since the program was started live_words Number of words of live data in the major heap including the header words live_blocks Number of live objects in the major heap free_words Number of words in the free list free_blocks Number of objects in the free list largest_free Size in words of the largest object in the free list fragments Number of wasted words due to fragmentation These are 1 words free blocks placed between two live objects They cannot be inserted in the free list thus they are not available for allocation compactions Number of heap compactions since the program was started The total amount of memory allocated by the program since it was started is in words minor_
64. directory inline n Set aggressiveness of inlining to n where n is a positive integer Specifying inline 0 prevents all functions from being inlined except those whose body is smaller than the call site Thus inlining causes no expansion in code size The default aggressiveness inline 1 allows slightly larger functions to be inlined resulting in a slight expansion in code size Higher values for the inline option cause larger and larger functions to become candidate for inlining but can result in a serious increase in code size linkall Forces all modules contained in libraries to be linked in If this flag is not given unreferenced modules are not linked in When building a library a flag setting the linkall flag forces all subsequent links of programs involving that library to link all the modules contained in the library o exec file Specify the name of the output file produced by the linker The default output name is a out in keeping with the Unix tradition If the a option is given specify the name of the library produced If the output obj option is given specify the name of the output file produced output obj Cause the linker to produce a C object file instead of an executable file This is useful to wrap Caml code as a C library callable from any C program See chapter 15 section 15 6 5 The name of the output object file is camlprog o by default it can be set with the o option p Generate extra code to
65. ellipsis and returns an object of the same type The type of Oo copy is different from type lt gt gt lt gt as each ellipsis represents a different set of methods Ellipsis actually behaves as a type variable let p new point 5 val p point lt obj gt let q Oo copy p val q point lt obj gt g move 7 p get_x q get_x int int 5 12 42 In fact Oo copy p will behave as p copy assuming that a public method copy with body lt gt has been defined in the class of p Objects can be compared using the generic comparison functions and lt gt Two objects are equal if and only if they are physically equal In particular an object and its copy are not equal let q 0o copy p val q point lt obj gt p q p p bool bool false true Other generic comparissons such as lt lt can also be used on objects The relation lt defines an unspecified but strict ordering on objets The ordering relationship between two objects is fixed once for all after the two objects have been created and it is not affected by mutation of fields Cloning and override have a non empty intersection They are interchangeable when used within an object and without overriding any field class copy object method copy lt gt end class copy object a method copy a end class copy object self method copy Oo copy self end
66. expr stream pattern pattern gt expr lt gt lt stream pat comp stream pat comp expr gt pattern when expr pattern expr ident 111 112 Stream expressions are bracketed by lt and gt They represent the concatenation of their components The component expr represents the one element stream whose element is the value of expr The component expr represents a sub stream For instance if both s and t are streams of integers then lt 1 s t 2 gt is a stream of integers containing the element 1 then the elements of s then those of t and finally 2 The empty stream is denoted by lt gt Unlike any other kind of expressions in the language stream expressions are submitted to lazy evaluation the components are not evaluated when the stream is built but only when they are accessed during stream matching The components are evaluated once the first time they are accessed the following accesses reuse the value computed the first time Stream patterns also bracketed by lt and gt describe initial segments of streams In particular the stream pattern lt gt matches all streams Stream pattern components are matched against the corresponding elements of a stream The component pattern matches the corresponding stream element against the pattern if followed by when the match is accepted only if the result of the guard expression is true The component pattern expr applies
67. expr is evaluated and its value becomes the value of the whole match expression The evaluation of expr takes place in an environment enriched by the bindings performed during matching If several patterns match the value of expr the one that occurs first in the match expression is selected If none of the patterns match the value of expr the exception Match_failure is raised Boolean operators The expression expr amp amp expr evaluates to true if both expr and expr evaluate to true oth erwise it evaluates to false The first component expr is evaluated first The second com ponent exprs is not evaluated if the first component evaluates to false Hence the expression expr amp amp expr behaves exactly as if expr then exprs else false The expression expr expr evaluates to true if one of expr and expr evaluates to true otherwise it evaluates to false The first component expr is evaluated first The second component exprs is not evaluated if the first component evaluates to true Hence the expression expr expr behaves exactly as if expr then true else exprs The boolean operator amp is synonymous for amp amp The boolean operator or is synonymous for 92 Loops The expression while expr do expry done repeatedly evaluates expry while expr evaluates to true The loop condition expr is evaluated and tested at the beginning of each iteration The whole while done expression evaluate
68. fib_closure NULL fib_closure caml_named_value fib return Int_val callback fib_closure Val_int n char format_result int n static value format_result_closure NULL if format_result_closure NULL format_result_closure caml_named_value format_result Chapter 15 Interfacing C with Objective Caml 189 return strdup String_val callback format_result_closure Val_int n We copy the C string returned by String_val to the C heap so that it remains valid after garbage collection We now compile the Caml code to a C object file and put it in a C library along with the stub code in modwrap c and the Caml runtime system ocamlc custom output obj o modcaml o mod ml ocamlc c modwrap c cp usr local lib ocaml libcamlrun a mod a ar r mod a modcaml o modwrap o One can also use ocamlopt output obj instead of ocamlc custom output obj In this case replace libcamlrun a the bytecode runtime library by libasmrun a the native code runtime library Now we can use the two fonctions fib and format_result in any C program just like regular C functions Just remember to call caml_startup once before File main c a sample client for the Caml functions include lt stdio h gt int main int argc char argv int result Initialize Caml code caml_startup argv Do some computation result fib 10 printf fib 10 s n format_result result return 0
69. from string buff starting at offset ofs to the output channel chan Raise Invalid_argument output if ofs and len do not designate a valid substring of buff output_byte out_channel gt int gt unit Write one 8 bit integer as the single character with that code on the given output channel The given integer is taken modulo 256 output_binary_int out_channel gt int gt unit Write one integer in binary format on the given output channel The only reliable way to read it back is through the input_binary_int function The format is compatible across all machines for a given version of Objective Caml output_value out_channel gt a gt unit Write the representation of a structured value of any type to a channel Circularities and sharing inside the value are detected and preserved The object can be read back by the function input_value See the description of module Marshal for more information output_value is equivalent to Marshal to_channel with an empty list of flags seek_out out_channel gt int gt unit seek_out chan pos sets the current writing position to pos for channel chan This works only for regular files On files of other kinds such as terminals pipes and sockets the behavior is unspecified pos_out out_channel gt int Return the current writing position for the given channel out_channel_length out_channel gt int Return the total length number of characters of the given cha
70. functions from structures to structures They are used to express parameterized structures a structure A parameterized by a structure B is simply a functor F with a formal parameter B along with the expected signature for B which returns the actual structure A itself The functor F can then be applied to one or several implementations B Bn of B yielding the corresponding structures A Any For instance here is a structure implementing sets as sorted lists parameterized by a structure providing the type of the set elements and an ordering function over this type used to keep the sets sorted type comparison Less Equal Greater type comparison Less Equal Greater module type ORDERED_TYPE sig type t val cmp t gt t gt comparison end module type ORDERED_TYPE sig type t val cmp t gt t gt comparison end module Set functor Elt ORDERED_TYPE gt struct Or N type element Elt t type set element list let empty let rec add x s match s with gt x hd tl gt match Elt cmp x hd with Equal gt s x is already in s Less a gt E x is smaller than all elements of s Greater gt hd add x tl let rec member x s match s with gt false hd tl gt match Elt cmp x hd with Equal gt true x belongs to s Less gt false x is smaller than all elements of s Great
71. functions must therefore be loaded explicitly in the debugger load_printer file name Load in the debugger the indicated cmo or cma object file The file is loaded in an envi ronment consisting only of the Objective Caml standard library plus the definitions provided by object files previously loaded using load_printer If this file depends on other object files not yet loaded the debugger automatically loads them if it is able to find them in the search path The loaded file does not have direct access to the modules of the program being debugged Chapter 13 The debugger ocamldebug 163 install_printer printer name Register the function named printer name a value path as a printer for objects whose types match the argument type of the function That is the debugger will call printer name when it has such an object to print The printing function printer name must use the Format library module to produce its output otherwise its output will not be correctly located in the values printed by the toplevel loop The value path printer name must refer to one of the functions defined by the object files loaded using load_printer It cannot reference the functions of the program being debugged remove_printer printer name Remove the named function from the table of value printers 13 9 Miscellaneous commands list module beginning end List the source of module module from line number beginning to line number end By default 20
72. given symbols as entry points for the grammar For each entry point a parsing function with the same name is defined in the output module Non terminals that are not declared as entry points have no such parsing function Start symbols must be given a type with the type directive below itype lt type gt symbol symbol Specify the type of the semantic attributes for the given symbols This is mandatory for start symbols only Other nonterminal symbols need not be given types by hand these types will be inferred when running the output files through the Objective Caml compiler unless the s option is in effect The type part is an arbitrary Caml type expression except that all type constructor names must be fully qualified as explained above for token left symbol symbol right symbol symbol nonassoc symbol symbol Associate precedences and associativities to the given symbols All symbols on the same line are given the same precedence They have higher precedence than symbols declared before in a Zleft 4right or Znonassoc line They have lower precedence than symbols declared 146 after in a Zleft right or 4nonassoc line The symbols are declared to associate to the left Aleft to the right Aright or to be non associative nonassoc The symbols are usually tokens They can also be dummy nonterminals for use with the prec directive inside the rules 11 4 3 Rules The syntax for rules is as usual nonter
73. gt sig type element Elt t concrete type set abstract val empty set val add element gt set gt set val member element gt set gt bool end module type SETFUNCTOR functor Elt ORDERED_TYPE gt sig type element Elt t and set val empty set val add element gt set gt set val member element gt set gt bool end module AbstractSet Set SETFUNCTOR module AbstractSet SETFUNCTOR module AbstractStringSet AbstractSet OrderedString module AbstractStringSet sig type element OrderedString t and set AbstractSet OrderedString set val empty set val add element gt set gt set val member element gt set gt bool end AbstractStringSet add gee AbstractStringSet empty AbstractStringSet set lt abstr gt In an attempt to write the type constraint above more elegantly one may wish to name the signature of the structure returned by the functor then use that signature in the constraint module type SET sig type element type set val empty set val add element gt set gt set val member element gt set gt bool end module type SET sig type element and set val empty set val add element gt set gt set val member element gt set gt bool end HH H H H module WrongSet Set functor Elt ORDERED_TYPE gt SET module WrongSet functor Elt
74. gt int gt unit pp_get_max_boxes formatter gt unit gt int pp_over_max_boxes formatter gt unit gt bool pp_set_ellipsis_text formatter gt string gt unit pp_get_ellipsis_text formatter gt unit gt string pp_set_formatter_out_channel formatter gt out_channel gt unit pp_set_formatter_output_functions formatter gt 226 string gt int gt int gt unit gt unit gt unit gt unit val pp_get_formatter_output_functions formatter gt unit gt string gt int gt int gt unit unit gt unit val pp_set_all_formatter_output_functions formatter gt string gt int gt int gt unit gt unit gt unit gt unit gt unit gt int gt unit gt unit val pp_get_all_formatter_output_functions formatter gt unit gt string gt int gt int gt unit unit gt unit unit gt unit int gt unit The basic functions to use with formatters These functions are the basic ones usual functions operating on the standard formatter are defined via partial evaluation of these primitives For instance print_string is equal to pp_print_string std_formatter val fprintf formatter gt a formatter unit format gt a fprintf ff format argi argN formats the arguments arg1 to argN according to the format string format and outputs the resulting string on the formatter ff The format is a character string whic
75. implement critical sections and protect shared mutable data structures against concurrent accesses The typical use is if m is the mutex associated with the data structure D Mutex lock m Critical section that operates over D Mutex unlock m type t The type of mutexes val create unit gt t Return a new mutex val lock t gt unit Lock the given mutex Only one thread can have the mutex locked at any time A thread that attempts to lock a mutex already locked by another thread will suspend until the other thread unlocks the mutex val try_lock t gt bool Same as try_lock but does not suspend the calling thread if the mutex is already locked just return false immediately in that case If the mutex is unlocked lock it and return true val unlock t gt unit Unlock the given mutex Other threads suspended trying to lock the mutex will restart 21 3 Module Condition condition variables to synchronize between threads Condition variables are used when one thread wants to wait until another thread has finished doing something the former thread waits on the condition variable the latter thread signals the condition when it is done Condition variables should always be protected by a mutex The typical use is if D is a shared data structure m its mutex and c is a condition variable Mutex lock m while some predicate P over D is not satisfied do Condition wait c m done Modify D i
76. in the definitions that follow its own A class binding binds the class name class name to the value of expression class expr It also binds the class type class name to the type of the class and defines two type abbreviations class name and class name The first one is the type of objects of this class while the second is more general as it unifies with the type of any object belonging to a subclass see section 5 4 Virtual class A class must be flagged virtual if one of its methods is virtual that is appears in the class type but is not actually defined Objects cannot be created from a virtual class Type parameters The class type parameters correspond to the ones of the class type and of the two type abbreviations defined by the class binding They must be bound to actual types in the class definition using type constraints So that the abbreviations are well formed type variables of the inferred type of the class must either be type parameters or be bound in the constraint clause 5 9 4 Class specification class specification class class spec and class spec class spec virtual type parameters class name class type This is the counterpart in signatures of class definitions A class specification matches a class definition if they have the same type parameters and their types match 5 9 5 Class type definitions classtype definition class type classtype def and classtype def classtype def vi
77. initializer Therefore is can access self and the instance variables class printable_point x_init let origin x_init 10 10 in object self Chapter 2 Objects in Caml 29 val mutable x origin method get_x x method move d x lt x d method print print_int self get_x initializer print_string new point at self print print_newline end class printable_point int gt object val mutable x int method get_x int method move int gt unit method print unit end H H HF H H let p new printable_point 17 new point at 10 val p printable_point lt obj gt Initializers cannot be overridden On the contrary all initializers are evaluated sequentially Ini tializers are particularly useful to enforce invariants Another example can be seen in section 4 1 2 4 Virtual methods It is possible to declare a method without actually defining it using the keyword virtual This method will be provided latter in subclasses A class containing virtual methods must be flagged virtual and cannot be instantiated that is no object of this class can be created It still defines abbreviations treating virtual methods as other methods class virtual abstract_point x_init object self val mutable x x_init method virtual get_x int method get_offset self get_x x_init method virtual move int gt unit end class virtual abstract_point int gt object val mutable x in
78. lines of the current module are displayed starting 10 lines before the current position source filename Read debugger commands from the script filename 13 10 Running the debugger under Emacs The most user friendly way to use the debugger is to run it under Emacs See the file emacs README in the distribution for information on how to load the Emacs Lisp files for Caml support The Caml debugger is started under Emacs by the command M x camldebug with argument the name of the executable file progname to debug Communication with the debugger takes place in an Emacs buffer named camldebug progname The editing and history facilities of Shell mode are available for interacting with the debugger In addition Emacs displays the source files containing the current event the current posi tion in the program execution and highlights the location of the event This display is updated synchronously with the debugger action The following bindings for the most common debugger commands are available in the camldebug progname buffer C c C s command step execute the program one step forward C c C k command backstep execute the program one step backward C c C n command next execute the program one step forward skipping over function calls Middle mouse button command display display named value n under mouse cursor support incremental browsing of large data structures 164 C c C p command print print value of ident
79. link multithreaded programs in combination with the threads library described in chapter 21 What this option actually does is select a special thread safe version of the standard library unsafe Turn bound checking off on array and string accesses the v i and s i constructs Programs compiled with unsafe are therefore faster but unsafe anything can happen if the program accesses an array or string outside of its bounds v Print the version number of the compiler w warning list Enable or disable warnings according to the argument warning list The argument is a string of one or several characters with the following meaning for each character A a enable disable all warnings F f enable disable warnings for partially applied functions ie f x expr where the appli cation f x has a function type M m enable disable warnings for overriden methods Chapter 10 Native code compilation ocamlopt 139 P p enable disable warnings for partial matches missing cases in pattern matchings S s enable disable warnings for statements that do not have type unit e g exprl expr2 when ezpr1 does not have type unit U u enable disable warnings for unused redundant match cases V v enable disable warnings for hidden instance variables X x enable disable all other warnings The default setting is w A all warnings enabled 10 3 Common errors The error messages are almost identical to those of ocamlc See section 7 4
80. list method is_empty repr method mem x List exists x repr method add x lt repr merge x repr gt method union s b lt repr merge repr s tag gt method iter f a gt unit List iter f repr HH HHH HH HH HHH HHH HHH HH HAF HH HH OH OF OH OF OF Chapter 4 Advanced examples with classes and modules 69 method tag repr end end 4 3 The subject observer pattern The following example known as the subject observer pattern is often presented in the literature as a difficult inheritance problem with inter connected classes The general pattern amounts to the definition a pair of two classes that recursively interact with one another The class observer has a distinguished method notify that requires two arguments a subject and an event to execute an action class virtual subject event observer object method virtual notify subject gt event gt unit end class virtual a b observer object method virtual notify a gt b gt unit end The class subject remembers a list of observers in an instance variable and has a distinguished method notify_observers to broadcast the message notify to all observers with a particular event e class observer event subject object self val mutable observers observer list method add_observer obs observers lt obs observers method notify_observers e
81. method get_x int method move int gt functional_point end let p new functional_point 7 val p functional_point lt obj gt p get_x int 7 p move 3 get_x int 10 pH get_x int 7 While objects of either class will behave the same objects of their subclasses will be different In a subclass of the latter the method move will keep returning an object of the parent class On the contrary in a subclass of the former the method move will return an object of the subclass Functional update is often used in conjunction with binary methods as illustrated in section 4 2 1 2 12 Cloning objects Objects can also be cloned whether they are functional or imperative The library function 0o copy makes a shallow copy of an object That is it returns an object that is equal to the previous one The instance variables have been copied but their contents are shared Assigning a new value to an instance variable of the copy using a method call will not affect instance variables of the original and conversely A deeper assignment for example if the instance variable if a reference cell will of course affect both the original and the copy The type of 0o copy is the following Oo copy gt as a gt a lt fun gt The keyword as in that type binds the type variable a to the object type lt gt Therefore Oo copy takes an object with any methods represented by the
82. name instead of path accesses module path name The scope of the open stops at the end of the signature expression 106 Including a signature The expression include modtype path in a signature performs textual inclusion of the components of the signature denoted by modtype path It behaves as if the components of the included signature were copied at the location of the include The modtype path argument must refer to a module type that is a signature 5 10 3 Functor types The module type expression functor module name module type gt module type is the type of functors functions from modules to modules that take as argument a module of type module type and return as result a module of type module type The module type module type can use the name module name to refer to type components of the actual argument of the functor No restrictions are placed on the type of the functor argument in particular a functor may take another functor as argument higher order functor 5 10 4 The with operator Assuming module type denotes a signature the expression module type with mod constraint and mod constr denotes the same signature where type equations have been added to some of the type spec ifications as described by the constraints following the with keyword The constraint type type parameters typeconstr typexp adds the type equation typexp to the specification of the type component named typeconstr of the con
83. nothing else Str regexp_string_case_fold is similar but the regexp matches in a case insensitive way String matching and searching val val val val string_match regexp gt string gt int gt bool string_match r s start tests whether the characters in s starting at position start match the regular expression r The first character of a string has position 0 as usual search_forward regexp gt string gt int gt int search_forward r s start searchs the string s for a substring matching the regular expression r The search starts at position start and proceeds towards the end of the string Return the position of the first character of the matched substring or raise Not_found if no substring matches search_backward regexp gt string gt int gt int Same as search_forward but the search proceeds towards the beginning of the string string_partial_match regexp gt string gt int gt bool Similar to string_match but succeeds whenever the argument string is a prefix of a string that matches This includes the case of a true complete match Chapter 20 The str library regular expressions and string processing 289 val matched_string string gt string matched_string s returns the substring of s that was matched by the latest string_match search_forward or search_backward The user must make sure that the parameter s is the same string that was passed to the matching or searching function va
84. of bytecode object files val init unit gt unit Initialize the library Must be called before loadfile val loadfile string gt unit Load the given bytecode object file and link it All toplevel expressions in the loaded compilation unit are evaluated No facilities are provided to access value names defined by the unit Therefore the unit must register itself its entry points with the main program e g by modifying tables of functions val loadfile_private string gt unit Same as loadfile except that the module loaded is not made available to other modules dynamically loaded afterwards val add_interfaces string list gt string list gt unit 311 312 add_interfaces units path grants dynamically linked object files access to the compilation units named in list units The interfaces cmi files for these units are searched in path a list of directory names Initially dynamically linked object files do not have access to any of the compilation units composing the running program not even the standard library add_interfaces or add_available_units see below must be called to grant access to some of the units val add_available_units string Digest t list gt unit Same as add_interfaces but instead of searching cmi files to find the unit interfaces uses the interface digests given for each unit This way the cmi interface files need not be available at run time The digests can be extracted from cm
85. of the functor Map Make t is the type of the map keys compare is a total ordering function over the keys This is a two argument function f such that f e1 e2 is zero if the keys e1 and e2 are equal f e1 e2 is strictly negative if e1 is smaller than e2 and f e1 e2 is strictly positive if e1 is greater than e2 Example a suitable ordering function is the generic structural comparison function compare module type S sig type key The type of the map keys type a t The type of maps from type key to type a val empty at The empty map val add key gt a gt at gt at add x y m returns a map containing the same bindings as m plus a binding of x to y If x was already bound in m its previous binding disappears val find key gt at gt a find x mreturns the current binding of x in m or raises Not_found if no such binding exists val remove key gt at gt at remove x mreturns a map containing the same bindings as m except for x which is unbound in the returned map val mem key gt a t gt bool mem x m returns true if m contains a binding for m and false otherwise 240 val iter key gt a gt unit gt a t gt unit iter f m applies f to all bindings in map m f receives the key as first argument and the associated value as second argument The order in which the bindings are passed to f is unspecified Only current bindings are presented to f bindings hidden by
86. of the side effecting function f It is equivalent to f x except that no warning is generated String conversion functions val string_of_bool bool gt string Return the string representation of a boolean val bool_of_string string gt bool Convert the given string to a boolean Raise Invalid_argument bool_of_string if the string is not true or false val string_of_int int gt string Return the string representation of an integer in decimal val int_of_string string gt int Convert the given string to an integer The string is read in decimal by default or in hexadecimal octal or binary if the string begins with Ox Oo or Ob respectively Raise Failure int_of_string if the given string is not a valid representation of an integer val string_of_float float gt string Return the string representation of a floating point number val float_of_string string gt float Convert the given string to a float The result is unspecified if the given string is not a valid representation of a float 202 Pair operations val fst a b gt a Return the first component of a pair val snd a b gt b Return the second component of a pair List operations More list operations are provided in module List val a list gt a list gt a list List concatenation Input output type in_channel type out_channel The types of input channels and output channels
87. options are required on the final linking phase that links to gether the object file produced by the output obj option and the remainder of the program Those options are shown in the configuration file config Makefile generated during compilation of Ob jective Caml as the variables BYTECCLINKOPTS for object files produced by ocamlc output obj and NATIVECCLINKOPTS for object files produced by ocamlopt output obj Currently the only ports that require special attention are e Digital Unix on the Alpha object files produced by ocamlc output obj must be linked with the taso option This is not necessary for object files produced by ocamlopt output obj e Windows NT the object file produced by Objective Caml have been compiled with the MT flag and therefore all other object files linked with it should also be compiled with MT 15 7 A complete example This section outlines how the functions from the Unix curses library can be made available to Objective Caml programs First of all here is the interface curses mli that declares the curses primitives and data types type window The type window remains abstract external initscr unit gt window curses_initscr external endwin unit gt unit curses_endwin external refresh unit gt unit curses_refresh external wrefresh window gt unit curses_wrefresh external newwin int gt int gt int gt int gt window curses_newwin external mvwin w
88. printf lt Window d lt s gt n s identity string_of_event e end class a trace_observer object constraint a lt identity int gt method notify a gt event gt unit end and attached several observers to the same object let window new richer_window_subject val window lt notify a gt event gt unit gt richer_window_subject as a lt obj gt window tadd_observer new richer_window_observer Characters 21 47 This expression has type lt draw unit raise unit gt as a richer_window_observer lt notify a gt event gt unit gt but is here used with type lt notify b richer_window_subject as c gt event gt unit gt as b Type a is not compatible with type lt notify d gt event gt unit gt as e richer_window_subject as d lt add_observer lt notify Cf richer_window_subject as g gt event gt unit gt as f gt unit draw unit identity int move int gt unit notify_observers event gt unit raise unit resize int gt unit gt window tadd_observer new trace_observer Characters 21 39 This expression has type lt identity int gt as a trace_observer lt notify a gt event gt unit gt but is here used with type lt notify b richer_window_subject as c gt event gt unit gt as b Type a is not com
89. prints str in the current box val print_as int gt string gt unit print_as len str prints str in the current box The pretty printer formats str as if it were of length len val print_int int gt unit Print an integer in the current box val print_float float gt unit Print a floating point number in the current box val print_char char gt unit Print a character in the current box val print_bool bool gt unit Print an boolean in the current box Break hints val print_space unit gt unit print_space is used to separate items typically to print a space between two words It indicates that the line may be split at this point It either prints one space or splits the line It is equivalent to print_break 1 0 val print_cut unit gt unit print_cut is used to mark a good break position It indicates that the line may be split at this point It either prints nothing or splits the line This allows line splitting at the current point without printing spaces or adding indentation It is equivalent to print_break 0 0 val print_break int gt int gt unit Insert a break hint in a pretty printing box print_break nspaces offset indicates that the line may be split a newline character is printed at this point if the contents of the current box does not fit on one line If the line is split at that point offset is added to the current indentation If the line is not split n
90. prints the inferred type and result value if any The system prints a sharp prompt before reading each phrase Input to the toplevel can span several lines It is terminated by a double semicolon The toplevel input consists in one or several toplevel phrases with the following syntax toplevel input toplevel phrase toplevel phrase definition expr ident directive argument definition let rec let binding and let binding external value name typexpr external declaration type definition exception definition module module name module type module expr module type modtype name module type open module path directive argument nothing string literal integer literal value path A phrase can consist of a definition similar to those found in implementations of compilation units or in struct end module expressions The definition can bind value names type names an exception a module name or a module type name The toplevel system performs the bindings then prints the types and values if any for the names thus defined A phrase may also consist in a open directive see section 5 11 or a value expression sec tion 5 7 Expressions are simply evaluated without performing any bindings and the value of the expression is printed 125 126 Finally a phrase can also consist in a toplevel directive starting with the sharp sign These directives control the behavior of the to
91. quote characters The two single quotes enclose either one character different from and or one of the escape sequences below Sequence Character denoted backslash single quote n linefeed LF r return CR t horizontal tabulation TAB b backspace BS ddd the character with ASCII code ddd in decimal String literals string literal string character regular char VA n t x 0 9 0 9 0 9 string character String literals are delimited by double quote characters The two double quotes enclose a sequence of either characters different from and or escape sequences from the table below Sequence Character denoted backslash double quote n linefeed LF r return CR t horizontal tabulation TAB b backspace BS ddd the character with ASCII code ddd in decimal To allow splitting long string literals across lines the sequence newline blanks a at end of line followed by any number of blanks at the beginning of the next line is ignored inside string literals The current implementation places no restrictions on the length of string literals Prefix and infix symbols infix symbol lt gt 7 1 amp 4 operator char prefix symbol 7 operator char operator char amp lt l gt 7 7 117 Sequences of operator characters such as lt
92. read file_descr gt string gt int gt int gt int read fd buff ofs len reads len characters from descriptor fd storing them in string buff starting at position ofs in string buff Return the number of characters actually read val write file_descr gt string gt int gt int gt int write fd buff ofs len writes len characters to descriptor fd taking them from string buff starting at position ofs in string buff Return the number of characters actually written Interfacing with the standard input output library val in_channel_of_descr file_descr gt in_channel Create an input channel reading from the given descriptor The channel is initially in binary mode use set_binary_mode_in ic false if text mode is desired val out_channel_of_descr file_descr gt out_channel Create an output channel writing on the given descriptor The channel is initially in binary mode use set_binary_mode_out oc false if text mode is desired val descr_of_in_channel in_channel gt file_descr Return the descriptor corresponding to an input channel val descr_of_out_channel out_channel gt file_descr Return the descriptor corresponding to an output channel Chapter 18 The unix library Unix system calls 263 Seeking and truncating type seek_command SEEK_SET SEEK_CUR SEEK_END Positioning modes for lseek SEEK_SET indicates positions relative to the beginning of the file SEEK_CUR relative to the current po
93. representing the defined type by giving the list of associated constructors if it is a variant type or associated labels if it is a record type If no type representation is given nothing is assumed on the structure of the type besides what is stated in the optional type equation The type representation constr decl constr decl describes a variant type The constructor declarations constr decl constr decl describe the constructors associated to this variant type The constructor declaration ncconstr name of typexpr declares the name ncconstr name as a non constant constructor whose argument has type typexpr The constructor declaration cconstr name declares the name cconstr name as a constant constructor Constructor names must be capitalized The type representation label decl label decl describes a record type The label declarations label decl label decl describe the labels associated to this record type The label declaration label name typexpr declares label name as a label whose argument has type typexpr The label declaration mutable label name typexpr behaves similarly in addition it allows physical modification over the argument to this label The two components of a type definition the optional equation and the optional representation can be combined independently giving rise to four typical situations Abstract type no equation no representation When appearing in a module signature this defin
94. signature is written module module name module type where module name is the name of the module component and module type its expected type Modules can be nested arbitrarily in particular functors can appear as components of structures and functor types as components of signatures For specifying a module component that is a functor one may write module module name name module type name module type module type instead of module module name functor name module type gt gt module type Module type specifications A module type component of a signature can be specified either as a manifest module type or as an abstract module type An abstract module type specification module type modtype name allows the name modtype name to be implemented by any module type in a matching signature but hides the implementation of the module type to all users of the signature A manifest module type specification module type modtype name module type requires the name modtype name to be implemented by the module type module type in a matching signature but makes the equality between modtype name and module type apparent to all users of the signature Opening a module path The expression open module path in a signature does not specify any components It simply affects the parsing of the following items of the signature allowing components of the module denoted by module path to be referred to by their simple names
95. string method concat a gt a method copy a method get string gt int gt char method print unit method repr string method set string gt int gt char gt unit method sub int gt int gt a end Another constructor of the class string can be defined to return an uninitialized string of a given length class cstring n ostring String create n class cstring int gt ostring Here exposing the representation of strings is probably harmless We do could also hide the representation of strings as we hid the currency in the class money of section 2 15 Stacks There is sometimes an alternative between using modules or classes for parametric data types Indeed there are situations when the two approaches are quite similar For instance a stack can be straightforwardly implemented as a class exception Empty exception Empty class a stack object val mutable 1 a list method push x 1 lt x 1 method pop match 1 with gt raise Empty a 1 gt 1 lt 1 a method clear 1 lt method length List length 1 end HHHH FF 66 class a stack object val mutable 1 a list method clear unit method length int method pop a method push a gt unit end However writing a method for iterating over a stack is more problematic A method fold would have type b gt a gt b gt b gt b He
96. that can run on this custom runtime This is achieved by the make_runtime and use_runtime flags to ocamlc For example to build a custom runtime system integrating the C parts of the unix and threads libraries do ocamlc make runtime o home me ocamlunixrun unix cma threads cma cclib lunix cclib lthreads To generate a bytecode executable that runs on this runtime system do ocamlc use runtime home me ocamlunixrun o myprog unix cma threads cma your cmo and cma files The bytecode executable myprog can then be launched as usual myprog args or home me ocamlunixrun myprog args Notice that the bytecode libraries unix cma and threads cma must be given twice when building the runtime system so that ocamlc knows which C primitives from lunix and 1threads are required and also when building the bytecode executable so that the bytecode from unix cma and threads cma is actually linked in 15 2 The value type All Caml objects are represented by the C type value defined in the include file cam1 mlvalues h along with macros to manipulate values of that type An object of type value is either e an unboxed integer e a pointer to a block inside the heap such as the blocks allocated through one of the alloc_ functions below e a pointer to an object outside the heap e g a pointer to a block allocated by malloc or to a C variable 15 2 1 Integer values Integer values encode 31 bit signed integers 63
97. that is the frame that called the selected frame An argument says how many frames to go up down count Select and display the stack frame just below the selected frame that is the frame that was called by the selected frame An argument says how many frames to go down 13 7 Examining variable values The debugger can print the current value of simple expressions The expressions can involve program variables all the identifiers that are in scope at the selected program point can be accessed Expressions that can be printed are a subset of Objective Caml expressions as described by the following grammar expr lowercase ident capitalized ident lowercase ident integer expr lowercase ident expr integer expr integer expr expr The first two cases refer to a value identifier either unqualified or qualified by the path to the structure that define it refers to the result just computed typically the value of a function application and is valid only if the selected event is an after event typically a function appli cation integer refer to a previously printed value The remaining four forms select part of an expression respectively a record field an array element a string element and the current contents of a reference print variables Print the values of the given variables print can be abbreviated as p 160 display variables Same as print but limit the dept
98. the bytecode compiler ocamlc receives two arguments a pointer to an array of Caml values the values for the arguments and an integer which is the number of arguments provided The other function to be used in conjunction with the native code compiler ocamlopt takes its arguments directly For instance here are the two C functions for the 7 argument primitive Nat add_nat value add_nat_native value nati value ofsi value leni value nat2 value ofs2 value len2 value carry_in value add_nat_bytecode value argv int argn return add_nat_native argv 0 argv 1 argv 2 argv 3 argv 4 argv 5 argv 6 Chapter 15 Interfacing C with Objective Caml 171 The names of the two C functions must be given in the primitive declaration as follows external name type bytecode C function name_ native code C function name For instance in the case of add_nat the declaration is external add_nat nat gt int gt int gt nat gt int gt int gt int gt int add_nat_bytecode add_nat_native Implementing a user primitive is actually two separate tasks on the one hand decoding the arguments to extract C values from the given Caml values and encoding the return value as a Caml value on the other hand actually computing the result from the arguments Except for very simple primitives it is often preferable to have two distinct C functions to implement these two tasks The first function actually implements
99. the sequence of bytes produced In particular this guarantees that marshaling always terminates Sharing between values marshaled by successive calls to Marshal to_channel is not detected though If flags contains Marshal No_sharing sharing is ignored This results in faster marshaling if v contains no shared substructures but may cause slower marshaling and larger byte representations if v actually contains sharing or even non termination if v contains cycles If flags does not contain Marshal Closures marshaling fails when it encounters a functional value inside v only pure data structures containing neither functions nor objects can safely be transmitted between different programs If flags contains Marshal Closures functional values will be marshaled as a position in the code of the program In this case the output of marshaling can only be read back in processes that run exactly the same program with exactly the same compiled code This is checked at un marshaling time using an MD5 digest of the code transmitted along with the code position val to_string a gt extern_flags list gt string Marshal to_string v flags returns a string containing the representation of v as a sequence of bytes The flags argument has the same meaning as for Marshal to_channel val to_buffer string gt int gt int gt a gt extern_flags list gt int Marshal to_buffer buff ofs len v flags marshals the value v storing its
100. token parse keywordi KWD1 keyword2 KWD2 keyword100 KWD100 A Z 1a Zz PA Z 2a 2 z 20 3a IDENT Lexing lexeme lexbuf Chapter 11 Lexer and parser generators ocamllex ocamlyacc 149 To keep the generated automata small rewrite those definitions with only one general iden tifier rule followed by a hashtable lookup to separate keywords from identifiers let keyword_table Hashtbl create 53 let _ List iter fun kwd tok gt Hashtbl add keyword_table kwd tok keywordi KWD1 keyword2 KWD2 keyword100 KWD100 rule token parse ASZ aer PA aA gg ra T oe let id Lexing lexeme lexbuf in try Hashtbl find keyword_table s with Not_found gt IDENT s 150 Chapter 12 Dependency generator ocamldep The ocamldep command scans a set of Objective Caml source files m1 and m1i files for references to external compilation units and outputs dependency lines in a format suitable for the make utility This ensures that make will compile the source files in the correct order and recompile those files that need to when a source file is modified The typical usage is ocamldep options mli ml gt depend where mli ml expands to all source files in the current directory and depend is the file that should contain the dependencies See below for a typical Makefile Dependencies are generated both for compiling with the bytecode compiler ocamlc and w
101. two types of objects plain characters which are simply copied to the output channel and conversion specifications each of which causes conversion and printing of one argument Conversion specifications consist in the character followed by optional flags and field widths followed by one conversion character The conversion characters and their meanings are d or i convert an integer argument to signed decimal u convert an integer argument to unsigned decimal x convert an integer argument to unsigned hexadecimal using lowercase letters 244 X convert an integer argument to unsigned hexadecimal using uppercase letters s insert a string argument c insert a character argument f convert a floating point argument to decimal notation in the style dddd ddd e or E convert a floating point argument to decimal notation in the style d ddd e dd mantissa and exponent g or G convert a floating point argument to decimal notation in style f or e E whichever is more compact b convert a boolean argument to the string true or false a user defined printer Takes two arguments and apply the first one to outchan the current output channel and to the second argument The first argument must therefore have type out_channel gt b gt unit and the second b The output produced by the function is therefore inserted in the output of fprintf at the current point t same as a but takes only one argument with type ou
102. unit method withdraw Euro c gt Euro c end However the bug might be fixed more safely by the following definition class safe_account object inherit account as unsafe method deposit x if zero leq x then unsafe deposit x else raise Invalid_argument deposit Chapter 4 Advanced examples with classes and modules 59 end class safe_account object val mutable balance Euro c method balance Euro c method deposit Euro c gt unit method withdraw Euro c gt Euro c end In particular this does not require the knowledge of the implementation of the method deposit To keep trace of operations we extend the class with a mutable field history and a private method trace to add an operation in the log Then each method to be traced is redefined type a operation Deposit of a Retrieval of a type a operation Deposit of a Retrieval of a class account_with_history object self inherit safe_account as super val mutable history method private trace x history lt x history method deposit x self trace Deposit x super deposit x method withdraw x self trace Retrieval x super withdraw x method history List rev history end class account_with_history object val mutable balance Euro c val mutable history Euro c operation list method balance Euro c method deposit Euro c gt unit method history Euro c operati
103. waits for a non ignored non blocked signal to be delivered On return the blocked signals are reset to their initial value val pause unit gt unit Wait until a non ignored non blocked signal is delivered Chapter 18 The unix library Unix system calls 269 Time functions type process_times tms_utime float User time for the process tms_stime float System time for the process tms_cutime float User time for the children processes tms_cstime float System time for the children processes The execution times CPU times of a process type tm tm_sec int Seconds 0 59 tm_min int Minutes 0 59 tm_hour int Hours 0 23 tm_mday int Day of month 1 31 tm_mon int Month of year 0 11 tm_year int Year 1900 tm_wday int Day of week Sunday is 0 tm_yday int Day of year 0 365 tm_isdst bool Daylight time savings in effect val val val val val val The type representing wallclock time and calendar date time unit gt float Return the current time since 00 00 00 GMT Jan 1 1970 in seconds gettimeofday unit gt float Same as time but with resolution better than 1 second gmtime float gt tm Convert a time in seconds as returned by time into a date and a time Assumes Greenwich meridian time zone also known as UTC localtime float gt tm Convert a time in secon
104. window can be edited at all times with the standard Windows interface An history of previously entered phrases is maintained and displayed in a separate window To quit the Camlwin application either select Quit from the File menu or use the quit function described below At any point the parsing compilation or evaluation of the current phrase can be interrupted by selecting the Interrupt Caml Light menu item This goes back to the prompt 8 1 Options The following command line options are recognized by the ocaml command I directory Add the given directory to the list of directories searched for source and compiled files By default the current directory is searched first then the standard library directory Directories added with I are searched after the current directory in the order in which they were given on the command line but before the standard library directory Directories can also be added to the search path once the toplevel is running with the directory directive section 8 2 rectypes Allow arbitrary recursive types during type checking By default only recursive types where the recursion goes through an object type are supported unsafe See the corresponding option for ocamlc chapter 7 Turn bound checking off on array and string accesses the v i and s i constructs Programs compiled with unsafe are therefore slightly faster but unsafe anything can happen if the program access
105. with callbacks 0 0 02000020000 2 eee IV The Objective Caml library 16 The core library 16 1 Module Pervasives the initially opened module 17 The standard library 17 1 17 2 17 3 17 4 17 5 17 6 17 7 17 8 17 9 17 10 17 11 17 12 17 13 17 14 17 15 17 16 17 17 17 18 17 19 17 20 17 21 17 22 17 23 17 24 17 25 17 26 17 27 17 28 17 29 Module Arg parsing of command line arguments ooo a a Module Array array operations ooo ee Module Buffer extensible string buffers o aoaaa a Module Callback registering Caml values with the C runtime Module Char character operations ooa a Module Digest MD5 message digest 2 a a ee Module Filename operations on filenames saoao a Module Format pretty printing oaoa a Module Gc memory management control and statistics so oaoa a a Module Genlex a generic lexical analyzer ooa a Module Hashtb1 hash tables and hash functions Module Lazy deferred computations s soo o e a Module Lexing the run time library for lexers generated by ocamllex Module List list operations ooa a Module Map association tables over ordered types ooo e 02004 Module Marshal marshaling of data structures 2 0200 Module Oo object oriented extension o o sooo e a a Module Parsing the run time library for parsers generated by ocamlyacc Module Printexc a catch a
106. x_init a object val mutable x x_init 1 method get x method set y x lt y end class a ref_succ 2a gt object constraint a int val mutable x int method get int method set int gt unit H H H H end 36 Let us consider a more realistic example We put an additional type constraint in method move since no free variables must remain uncaptured by a type parameter class a circle c a object val mutable center c method center center method set_center c center lt c method move center move int gt unit end class a circle 2a gt object constraint a lt move int gt unit gt val mutable center a method center a method move int gt unit method set_center a gt unit end An alternate definition of circle using a constraint clause in the class definition is shown below The type point used below in the constraint clause is an abbreviation produced by the definition of class point This abbreviation unifies with the type of any object belonging to a subclass of class point It actually expands to lt get_x int move int gt unit gt This leads to the following alternate definition of circle which has slightly stronger constraints on its argument as we now expect center to have a method get_x class a circle c a object constraint a point val mutable cente
107. 0000 elements length a list gt int Return the length number of elements of the given list hd a list gt a Return the first element of the given list Raise Failure hd if the list is empty tl a list gt a list Return the given list without its first element Raise Failure t1 if the list is empty nth a list gt int gt a Return the n th element of the given list The first element head of the list is at position 0 Raise Failure nth if the list is too short rev a list gt a list List reversal append a list gt a list gt a list Catenate two lists Same function as the infix operator Not tail recursive The operator is not tail recursive either rev_append a list gt a list gt a list List rev_append 11 12 reverses 11 and catenates it to 12 This is equivalent to List rev 11 12 but rev_append is tail recursive and more efficient concat a list list gt a list flatten a list list gt a list Catenate flatten a list of lists Not tail recursive length of the argument length of the longest sub list 236 Iterators val iter a gt unit gt a list gt unit List iter f a1 an applies function f in turn to al an It is equivalent to begin f al f a2 f an end val map a gt b gt a list gt b list List map f a1 an applies function f to a1
108. 17 type t string val val val val val val The type of digests 16 character strings string string gt t Return the digest of the given string substring string gt int gt int gt t Digest substring s ofs len returns the digest of the substring of s starting at character number ofs and containing len characters channel in_channel gt int gt t Digest channel ic len reads len characters from channel ic and returns their digest file string gt t Return the digest of the file whose name is given output out_channel gt t gt unit Write a digest on the given output channel input in_channel gt t Read a digest from the given input channel 17 7 Module Filename operations on file names val val val val current_dir_name string The conventional name for the current directory e g in Unix concat string gt string gt string concat dir file returns a file name that designates file file in directory dir is_relative string gt bool Return true if the file name is relative to the current directory false if it is absolute i e in Unix starts with is_implicit string gt bool Return true if the file name is relative and does not start with an explicit reference to the current directory or in Unix false if it starts with an explicit reference to the root directory or the current directory 218 val val val val val val c
109. 2 are the same array and the source and destination chunks overlap Raise Invalid_argument Array blit if o1 and len do not designate a valid subarray of v1 or if o2 and len do not designate a valid subarray of v2 214 val val val val val val val val to_list a array gt a list Array to_list a returns the list of all the elements of a of_list a list gt a array Array of_list 1 returns a fresh array containing the elements of 1 iter a gt unit gt a array gt unit Array iter f a applies function f in turn to all the elements of a It is equivalent to f a 0 f a 1 f a Array length a 1 map a gt b gt a array gt b array Array map f a applies function f to all the elements of a and builds an array with the results returned by f f a 0 f a 1 f a Array length a 1 iteri int gt a gt unit gt a array gt unit mapi int gt a gt b gt a array gt b array Same as Array iter and Array map respectively but the function is applied to the index of the element as first argument and the element itself as second argument fold_left a gt b gt a gt a gt b array gt a Array fold_left f x a computes f x a 0 a 1 a m 1 where n is the length of the array a fold_right b gt a gt a gt b array gt a gt a A
110. 2_OBJS Common rules OUFFIXES ml mli cmo cmi cmx ml cmo OCAMLC OCAMLFLAGS c lt mli cmi OCAMLC OCAMLFLAGS c lt ml cmx OCAMLOPT OCAMLOPTFLAGS c lt Clean up clean rm f progi prog2 rm f cm iox Dependencies depend OCAMLDEP INCLUDES mli ml gt depend include depend Chapter 13 The debugger ocamldebug This chapter describes the Objective Caml source level replay debugger ocamldebug Unix The debugger is available on Unix systems that provides BSD sockets Windows The debugger is not available 13 1 Compiling for debugging Before the debugger can be used the program must be compiled and linked with the g option all cmo and cma files that are part of the program should have been created with ocamlc g and they must be linked together with ocamlc g Compiling with g entails no penalty on the running time of programs object files and bytecode executable files are bigger and take longer to produce but the executable files run at exactly the same speed as if they had been compiled without g 13 2 Invocation 13 2 1 Starting the debugger The Objective Caml debugger is invoked by running the program ocamldebug with the name of the bytecode executable file as first argument ocamldebug options program arguments The arguments following program are optional and are passed as command line arguments to the program being debugged See
111. 3 13 1 Compiling for debugging 2 20 20 20 2 ee ee 153 1322 Invocation 2 4 Bowser Be eras Se eae a aE a SS re E ee a aA 153 13 3 Commands oe a siate Sea Pig Bes RE Bh owe ak Ek Sea Se Bt 154 13 4 Executing a Programi se a a D irea a Agee GB eae fe Bode Geet eos Saas ee 155 13 58 Breakpoints arnas oft ie ge A ee ee ee amp Ee eR eee ead ek ed 157 13 6 sPhevcallstack s Sesin foe ale p eee aoa ha kel eal a tle An eee ee kd 158 13 7 Examining variable values oaao ee 159 13 8 Controlling the debugger 2 aaa ee 160 13 9 Miscellaneous commands 2 2 0 ee ee 163 13 10 Running the debugger under Emacs 2 2 ee 163 14 Profiling ocamlprof 165 14 1 Compiling for profiling 2 pariga tioa a ene Yia anla aa a aa iih 165 14 2 Profiling an execution ooa aaa ee 166 14 3 Printing profiling information 0 a 166 14 4 Time profiling air eia siea wie Gib ase eo Be e Bae ee Sane eda ed 166 15 Interfacing C with Objective Caml 169 15 1 Overview and compilation information 0 00 0000 2 54s 169 15 2 Whervaliie type fife wick ene the ye oa dh pria Gi ee le on ean Gh ak 173 15 3 Representation of Caml datatypes 2 2 2 0 0000 eee ee ee 174 15 4 15 5 15 6 15 7 15 8 Operations on values 2 oaaae Living in harmony with the garbage collector 2 2200 Callbacks from Cto Caml Peg pe ke hag Ee eS A Po eS Bae Se ee A complete example ooa ee Advanced example
112. 8 End_of_file exception 195 environment 259 eprintf 227 244 eq_num 283 err_formatter 224 Error exception 249 312 error_message 259 312 escaped 216 252 establish_server 275 300 Event module 297 execv 260 299 execve 260 299 execvp 260 299 execvpe 260 exists 237 exists2 237 exit 208 294 Exit exception 195 exp 199 Failure exception 195 249 failwith 195 fchmod 264 fchown 264 file 217 file_exists 253 Filename module 217 fill 213 252 256 fill_arc 305 fill_circle 305 fill_ellipse 305 fill_poly 305 fill_rect 305 filter 237 find 231 237 310 find_all 231 237 first_chars 291 firstkey 310 317 flatten 235 float 200 246 float_of_int 200 float_of_num 284 float_of_string 201 floor 200 floor_num 282 flush 204 flush_str_formatter 225 fold_left 214 236 fold_left2 236 fold_right 214 236 fold_right2 236 for_all 237 for_all2 237 force 113 233 force_newline 221 foreground 303 fork 260 Format module 218 formatter_of_buffer 224 formatter_of_out_channel 224 fprintf 226 243 frexp 200 from 250 from_channel 234 241 from_function 234 from_string 234 242 fst 202 fstat 264 ftruncate 263 full_init 245 full_major 229 full_split 290 Gc module 227 ge_num 283 Genlex module 230 get 212 229 251 256 get_all_formatter_output_functions 224 get_approx_printing 285 get_ellipsis_text 223 get
113. By default parse recognizes a unit option help which will display usage_msg and the list of options and exit the program You can override this behaviour by specifying your own help option in speclist 212 exception Bad of string Functions in spec or anonfun can raise Arg Bad with an error message to reject invalid arguments val usage string spec string list gt string gt unit Arg usage speclist usage_msg prints an error message including the list of valid options This is the same message that Arg parse prints in case of error speclist and usage_msg are the same as for Arg parse val current int ref Position in Sys argv of the argument being processed You can change this value e g to force Arg parse to skip some arguments 17 2 Module Array array operations val length a array gt int Return the length number of elements of the given array val get a array gt int gt a Array get a n returns the element number n of array a The first element has number 0 The last element has number Array length a 1 Raise Invalid_argument Array get if n is outside the range 0 to Array length a 1 You can also write a n instead of Array get a n val set a array gt int gt a gt unit Array set a n x modifies array a in place replacing element number n with x Raise Invalid_argument Array set if n is outside the range 0 to Array length a 1 You can also write a n l
114. CAMLreturn result 182 Here the registering of result is not strictly needed because no allocation takes place after it gets its value but it s easier and safer to simply register all the local variables that have type value Here is the same function written using the low level allocation functions We notice that the cons cells are small blocks and can be allocated with alloc_smal11 and filled by direct assignments on their fields value alloc_list_int int i1 int i2 CAMLparam0 CAMLlocal2 result r r alloc_small 2 0 Allocate a cons cell Field r 0 Val_int i2 car the integer i2 Field r 1 Val_int 0 cdr the empty list result alloc_small 2 0 Allocate the other cons cell Field result 0 Val_int ii car the integer il Field result 1 r cdr the first cons cell CAMLreturn result In the two examples above the list is built bottom up Here is an alternate way that proceeds top down It is less efficient but illustrates the use of modify value alloc_list_int int i1 int i2 CAMLparam0 CAMLlocal2 tail r r alloc_small 2 0 Allocate a cons cell Field r 0 Val_int il car the integer il Field r 1 Val_int 0 A dummy value tail alloc_small 2 0 Allocate the other cons cell Field tail 0 Val_int i2 car the integer i2 Field tail 1 Val_int 0 cdr the empty list modify
115. Caml values Type abbreviations are not expanded when determining the arity of a primitive For instance type int_endo int gt int external f int_endo gt int_endo f external g int gt int gt int gt int f f has arity 1 but g has arity 2 This allows a primitive to return a functional value as in the f example above just remember to name the functional return type in a type abbreviation 15 1 2 Implementing primitives User primitives with arity n lt 5 are implemented by C functions that take n arguments of type value and return a result of type value The type value is the type of the representations for Caml values It encodes objects of several base types integers floating point numbers strings as well as Caml data structures The type value and the associated conversion functions and macros are described in details below For instance here is the declaration for the C function implementing the input primitive value input value channel value buffer value offset value length When the primitive function is applied in a Caml program the C function is called with the values of the expressions to which the primitive is applied as arguments The value returned by the function is passed back to the Caml program as the result of the function application User primitives with arity greater than 5 should be implemented by two C functions The first function to be used in conjunction with
116. Empty if the queue is empty peek a t gt a peek q returns the first element in queue q without removing it from the queue or raises Empty if the queue is empty clear a t gt unit Discard all elements from a queue length a t gt int Return the number of elements in a queue iter a gt unit gt a t gt unit iter f q applies f in turn to all elements of q from the least recently entered to the most recently entered The queue itself is unchanged 17 22 Module Random pseudo random number generator val val val init int gt unit Initialize the generator using the argument as a seed The same seed will always yield the same sequence of numbers full_init int array gt unit Same as init but takes more data as seed self_init unit gt unit Initialize the generator with a more or less random seed chosen in a system dependent way 246 val bits unit gt int Return 30 random bits in a nonnegative integer val int int gt int Random int bound returns a random integer between 0 inclusive and bound exclusive bound must be more than 0 and less than 2 val float float gt float Random float bound returns a random floating point number between 0 inclusive and bound exclusive If bound is negative the result is negative If bound is 0 the result is 0 17 23 Module Set sets over ordered types This module implements the set data structure give
117. The Objective Caml system release 2 04 Documentation and user s manual Xavier Leroy with Didier R my J r me Vouillon and Damien Doligez November 26 1999 Copyright 1999 Institut National de Recherche en Informatique et en Automatique Contents I An introduction to Objective Caml 1 The 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 core language BASICS ey amie or EE E a e a he Bes ees eee eee ee e G Datatypes e son eft eno aaa a nea St daa ana ih Bn ela a wera Bo RA Functions as values s onasan ae e n e a p ee Records and variants ooa a a Imperative features ooa ee Exc ptions ses misoa a Rete oe BLE Aad a e T elo ie bel ele A Symbolic processing of expressions ooo a Pretty printing and parsing ooa a a Standalone Caml programs oaoa a a 2 Objects in Caml 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 2 10 2 11 2 12 2 13 2 14 2 15 3 The 3 1 3 2 3 3 3 4 3 5 Classes andiiob jects asi 2 68 4 40 e Roto bo ete ee AO OS Se tc aed Referenc to self e g ele ee a he 2 Ae ae ee eR ates Mmnitializers 04 ae uke ede gels ye ek Gon Bene Se ee es ag Be es Be ed Virtual methods 2 eE a a aA a A a a a E a a a a a T A Private methods aoa 2 4 a Yoh tne Apso led a a a A a a hae E Class intertaces a irao hae a eh BON ee he I i ga AO NA Mier ane es e066 sees gg Phe ee BE eee Ane ee BO oe ek BS ee Multiple inheritance s oss 2 a ees ae ee ee he ee ed Parameterized classes e 22 0 2 44 oan hop
118. Thread module 294 ThreadUnix module 298 time 254 269 timed_read 299 timed_write 299 times 270 tl 235 to_buffer 241 to_channel 241 323 to_list 214 to_string 241 243 total_size 242 transp 306 truncate 200 263 try_lock 296 umask 264 uncapitalize 253 Unix module 257 Unix_error exception 259 unlink 264 unlock 296 uppercase 216 253 usage 212 utimes 270 wait 260 297 299 wait_next_event 307 wait_pid 295 wait_read 295 wait_signal 295 wait_timed_read 295 wait_timed_write 295 wait_write 295 waitpid 261 299 Weak module 256 white 303 word_size 254 wrap 298 wrap_abort 298 write 262 299 yellow 303 324 Index of keywords and see let type class 99 101 102 as 83 86 99 100 assert 113 begin 87 88 class 101 102 constraint 96 97 99 101 do see while for done see while for downto see for else see if end 87 88 97 99 103 106 107 exception 97 103 104 106 108 external 103 106 107 false 80 for 87 92 fun 87 89 99 function 87 89 functor 103 106 109 if 87 88 91 in see let 99 include 106 inherit 97 100 initializer 99 101 lazy 113 let 87 88 90 99 106 107 113 match 87 88 91 111 when 111 method 97 99 101 module 103 105 106 108 113 mutable 96 100 new 87 94 not 88 object 97 99 of see type exception open 103 105 106 109 or 87 88 91 pars
119. _dir string pw_shell string Structure of entries in the passwd database type group_entry val gr_name string gr_passwd string gr_gid int gr_mem string array Structure of entries in the groups database getlogin unit gt string Return the login name of the user executing the process 272 val getpwnam string gt passwd_entry Find an entry in passwd with the given name or raise Not_found val getgrnam string gt group_entry Find an entry in group with the given name or raise Not_found val getpwuid int gt passwd_entry Find an entry in passwd with the given user id or raise Not_found val getgrgid int gt group_entry Find an entry in group with the given group id or raise Not_found Internet addresses type inet_addr The abstract type of Internet addresses val inet_addr_of_string string gt inet_addr val string_of_inet_addr inet_addr gt string Conversions between string with the format XXX YYY ZZZ TTT and Internet addresses inet_addr_of_string raises Failure when given a string that does not match this format val inet_addr_any inet_addr A special Internet address for use only with bind representing all the Internet addresses that the host machine possesses Sockets type socket_domain PF_UNIX Unix domain PF_INET Internet domain The type of socket domains type socket_type SOCK_STREAM Stream socket SOCK_DGRAM D
120. _error_when_null_denominator 284 get_floating_ precision 285 318 get_formatter_output_functions 223 get_image 306 get_margin 221 get_max_boxes 221 get_max_indent 221 get_normalize_ratio 284 get_normalize_ratio_when_printing 285 getcwd 254 265 getegid 271 getenv 254 259 geteuid 271 getgid 271 getgrgid 272 getgrnam 272 getgroups 271 gethostbyaddr 275 gethostbyname 275 gethostname 275 getitimer 270 getlogin 271 getpeername 274 getpid 261 getppid 261 getprotobyname 275 getprotobynumber 276 getpwnam 272 getpwuid 272 getservbyname 276 getservbyport 276 getsockname 273 getsockopt 274 gettimeofday 269 getuid 271 global_replace 289 global_substitute 289 gmtime 269 Graphic_failure exception 302 Graphics module 302 green 303 group_beginning 289 group_end 289 gt_num 283 guard 298 handle_unix_error 259 hash 232 hash_param 233 HashedType module type 232 Hashtbl module 230 hd 235 header_size 242 id 294 ignore 201 in_channel_length 207 in_channel_of_descr 262 incr 208 incr_num 283 index 252 index_from 252 inet_addr_any 272 inet_addr_of_string 272 init 213 245 311 input 206 217 input_binary_int 207 input_byte 206 input_char 206 input_line 206 input_value 207 int 246 int_of_char 201 int_of_float 200 int_of_num 284 int_of_string 201 integer_num 282 interactive 254 invalid_arg 195 Invalid_argument excepti
121. _max_boxes max sets the maximum number of boxes simultaneously opened Material inside boxes nested deeper is printed as an ellipsis more precisely as the text returned by get_ellipsis_text Nothing happens if max is not greater than 1 val get_max_boxes unit gt int Return the maximum number of boxes allowed before ellipsis val over_max_boxes unit gt bool Test the maximum number of boxes allowed have already been opened 222 Advanced formatting val open_hbox unit gt unit open_hbox opens a new pretty printing box This box is horizontal the line is not split in this box new lines may still occur inside boxes nested deeper val open_vbox int gt unit open_vbox d opens a new pretty printing box with offset d This box is vertical every break hint inside this box leads to a new line When a new line is printed in the box d is added to the current indentation val open_hvbox int gt unit open_hvbox d opens a new pretty printing box with offset d This box is horizontal vertical it behaves as an horizontal box if it fits on a single line otherwise it behaves as a vertical box When a new line is printed in the box d is added to the current indentation val open_hovbox int gt unit open_hovbox d opens a new pretty printing box with offset d This box is horizontal or vertical break hints inside this box may lead to a new line if there is no more
122. _y unit gt int Return the size of the graphics window Coordinates of the screen pixels range over O size_x 1 and0 size_y 1 Drawings outside of this rectangle are clipped without causing an error The origin 0 0 is at the lower left corner Colors type color int A color is specified by its R G B components Each component is in the range 0 255 The three components are packed in an int OxRRGGBB where RR are the two hexadecimal digits for the red component GG for the green component BB for the blue component val rgb int gt int gt int gt color rgb r g b returns the integer encoding the color with red component r green component g and blue component b r g and b are in the range 0 255 val set_color color gt unit Set the current drawing color val black color val white color val red color val green color val blue color val yellow color val cyan color val magenta color Some predefined colors val background color val foreground color Default background and foreground colors usually either black foreground on a white background or white foreground on a black background clear_graph fills the screen with the background color The initial drawing color is foreground 304 Point and line drawing val val val val val val val val val plot int gt int gt unit Plot the given point with the current drawing color point_color in
123. a trailing plus sign denote one or several repetitions of the enclosed components Parentheses denote grouping 5 1 Lexical conventions Blanks The following characters are considered as blanks space newline horizontal tabulation carriage return line feed and form feed Blanks are ignored but they separate adjacent identifiers literals and keywords that would otherwise be confused as one single identifier literal or keyword Comments Comments are introduced by the two characters with no intervening blanks and terminated by the characters with no intervening blanks Comments are treated as blank characters Comments do not occur inside string or character literals Nested comments are handled correctly 75 76 Identifiers ident letter _ letter 0 9 _ letter A Z a z Identifiers are sequences of letters digits _ the underscore character and the single quote starting with a letter or an underscore Letters contain at least the 52 lowercase and uppercase letters from the ASCII set The current implementation also recognizes as letters all accented characters from the ISO 8859 1 ISO Latin 1 set and also allows an underscore _ as the first character of an identifier All characters in an identifier are meaningful The current implementation places no limits on the number of characters of an identifier Integer literals integer literal 0 9 H Ox 0x
124. act data types and so on From the file xz mli the ocamlopt compiler produces a compiled interface in the file x cmi The interface produced is identical to that produced by the bytecode compiler ocamlc e Arguments ending in ml are taken to be source files for compilation unit implementations Implementations provide definitions for the names exported by the unit and also contain expressions to be evaluated for their side effects From the file x m1 the ocamlopt compiler produces two files z o containing native object code and x cmx containing extra informa tion for linking and optimization of the clients of the unit The compiled implementation should always be referred to under the name z cmx when given a o file ocamlopt assumes that it contains code compiled from C not from Caml The implementation is checked against the interface file x mli if it exists as described in the manual for ocamlc chapter 7 135 136 Arguments ending in cmx are taken to be compiled object code These files are linked together along with the object files obtained by compiling m1 arguments if any and the Caml Light standard library to produce a native code executable program The order in which cmx and ml arguments are presented on the command line is relevant compilation units are initialized in that order at run time and it is a link time error to use a component of a unit before having initialized it Hence a given x cmx file must com
125. aining the representation s of the string class better_string s object val repr s method get n String get n method set n c String set nc method print print_string repr method copy lt repr String copy repr gt method sub start len lt repr String sub s start len gt end class better_string string gt object a val repr string method copy a method get string gt int gt char method print unit method set string gt int gt char gt unit method sub int gt int gt a end As shown in the inferred type the methods copy and sub now return objects of the same type as the one of the class Another difficulty is the implementation of the method concat In order to concatenate a string with another string of the same class one must be able to access the instance variable externally Thus a method repr returning s must be defined Here is the correct definition of strings Chapter 4 Advanced examples with classes and modules 65 class ostring s object self mytype val repr s method repr repr method get n String get n method set n c String set nc method print print_string repr method copy lt repr String copy repr gt method sub start len lt repr String sub s start len gt method concat t mytype lt repr repr t repr gt end class ostring string gt object a val repr
126. al and on integers lor Bitwise logical or on integers lxor Bitwise logical exclusive or on integers 1sl Bitwise logical shift left on integers lsr Bitwise logical shift right on integers asr Bitwise arithmetic shift right on integers Floating point addition infix Floating point subtraction prefix Floating point negation Floating point multiplication fs Floating point division xk Floating point exponentiation List concatenation String concatenation Dereferencing return the current contents of a reference Reference assignment update the reference given as first argument with the value of the second argument Structural equality test lt gt Structural inequality test Physical equality test l Physical inequality test lt Test less than lt Test less than or equal gt Test greater than gt Test greater than or equal 5 7 5 Objects Object creation When class path evaluates to a class body new class path evaluates to an object containing the instance variables and methods of this class When class path evaluates to a class function new class path evaluates to a function expecting the same number of arguments and returning a new object of this class Chapter 5 The Objective Caml language 95 Message sending The expression expr method name invokes the method method name of the object denoted by
127. aml exceptions val register string gt a gt unit Callback register n v registers the value v under the name n C code can later retrieve a handle to v by calling caml_named_value n val register_exception string gt exn gt unit Callback register_exception n exn registers the exception contained in the exception value exn under the name n C code can later retrieve a handle to the exception by calling caml_named_value n The exception value thus obtained is suitable for passign as first argument to raise_constant or raise_with_arg 17 5 Module Char character operations val code char gt int Return the ASCII code of the argument val chr int gt char Return the character with the given ASCII code Raise Invalid_argument Char chr if the argument is outside the range 0 255 val escaped char gt string Return a string representing the given character with special characters escaped following the lexical conventions of Objective Caml val lowercase char gt char val uppercase char gt char Convert the given character to its equivalent lowercase or uppercase character respectively 17 6 Module Digest MD5 message digest This module provides functions to compute 128 bit digests of arbitrary length strings or files The digests are of cryptographic quality it is very hard given a digest to forge a string having that digest The algorithm used is MD5 Chapter 17 The standard library 2
128. amlyacc This chapter describes two program generators ocamllex that produces a lexical analyzer from a set of regular expressions with associated semantic actions and ocamlyacc that produces a parser from a grammar with associated semantic actions These program generators are very close to the well known lex and yacc commands that can be found in most C programming environments This chapter assumes a working knowledge of lex and yacc while it describes the input syntax for ocamllex and ocamlyacc and the main differences with lex and yacc it does not explain the basics of writing a lexer or parser description in lex and yacc Readers unfamiliar with lex and yacc are referred to Compilers principles techniques and tools by Aho Sethi and Ullman Addison Wesley 1986 or Lex amp Yacc by Levine Mason and Brown O Reilly 1992 11 1 Overview of ocamllex The ocamllex command produces a lexical analyzer from a set of regular expressions with attached semantic actions in the style of lex Assuming the input file is lerer m11 executing ocamllex lexer m11 produces Caml code for a lexical analyzer in file Jerer m1 This file defines one lexing function per entry point in the lexer definition These functions have the same names as the entry points Lexing functions take as argument a lexer buffer and return the semantic attribute of the corresponding entry point Lexer buffers are an abstract data type implemented in the
129. and you should normally not have to change them set processcount count Set the maximum number of checkpoints to count More checkpoints facilitate going far back in time but use more memory and create more Unix processes As checkpointing is quite expensive it must not be done too often On the other hand backward execution is faster when checkpoints are taken more often In particular backward single stepping is more responsive when many checkpoints have been taken just before the current time To fine tune the checkpointing strategy the debugger does not take checkpoints at the same frequency for long displacements e g run and small ones e g step The two variables bigstep and smallstep contain the number of events between two checkpoints in each case set bigstep count Set the number of events between two checkpoints for long displacements set smallstep count Set the number of events between two checkpoints for small displacements The following commands display information on checkpoints and events info checkpoints Print a list of checkpoints info events module Print the list of events in the given module the current module by default 13 8 8 User defined printers Just as in the toplevel system section 8 2 the user can register functions for printing values of certain types For technical reasons the debugger cannot call printing functions that reside in the program being debugged The code for the printing
130. apter 3 The module system 55 As in the case of simple structures an alternate syntax is provided for defining functors and restricting their result module AbstractSet Elt ORDERED_TYPE SET with type element Elt t struct end Abstracting a type component in a functor result is a powerful technique that provides a high degree of type safety as we now illustrate Consider an ordering over character strings that is different from the standard ordering implemented in the OrderedString structure For instance we compare strings without distinguishing upper and lower case module NoCaseString struct type t string let cmp si s2 OrderedString cmp String lowercase s1 String lowercase s2 end module NoCaseString sig type t string val cmp string gt string gt comparison end module NoCaseStringSet AbstractSet NoCaseString module NoCaseStringSet sig type element NoCaseString t and set AbstractSet NoCaseString set val empty set val add element gt set gt set val member element gt set gt bool end NoCaseStringSet add FOO AbstractStringSet empty Characters 26 49 This expression has type AbstractStringSet set AbstractSet OrderedString set but is here used with type NoCaseStringSet set AbstractSet NoCaseString set Notice that the two types AbstractStringSet set and NoCaseStringSet set are not compatible and values of these two typ
131. arguments arg to arg As mentioned in chapter 7 in most cases the bytecode executable files produced by the ocamlc command are self executable and manage to launch the ocamlrun command on themselves auto matically That is assuming caml out is a bytecode executable file caml out arg arg works exactly as ocamlrun caml out arg argy Notice that it is not possible to pass options to ocamlrun when invoking caml out directly 9 2 Options The following command line option is recognized by ocamlrun v When set the memory manager prints some verbose messages on standard error 131 132 The following environment variables are also consulted OCAMLRUNPARAM Set the garbage collection parameters If OCAMLRUNPARAM is not set CAMLRUNPARAM will be used instead This variable must be a sequence of parameter specifications A parameter specification is an option letter followed by an sign a decimal number and an optional multiplier There are seven options the first six correspond to the fields of the control record documented in section 17 9 s minor_heap_size Size of the minor heap i major_heap_increment Minimum size increment for the major heap o space_overhead The major GC speed setting O max_overhead The heap compaction trigger setting v verbose What GC messages to print to stderr This is a sum of values selected from the following 1 Start of major GC cycle 2 Minor collection and major GC sl
132. ason is that sharp abbreviations carry an implicit anonymous variable that cannot be explicitly named Thus the abbreviation c0 should be expanded class c object self method m self lt m c1 gt as a gt cl end class c object method m ci end 2 11 Functional objects It is possible to write a version of class point without assignments on the instance variables The construct lt gt returns a copy of self that is the current object possibly changing the value of some instance variables class functional_point y object val x y method get_x x method move d lt x x d gt end class functional_point int gt object a val x int method get_x int method move int gt a end let p new functional_point 7 val p functional_point lt obj gt p get_x int 7 p move 3 get_x int 10 p get_x int 7 Note that the type abbreviation functional_point is recursive which can be seen in the class type of functional_point the type of self is a and a appears inside the type of the method move The above definition of functional_point is not equivalent to the following class bad_functional_point y object val x y method get_x x Chapter 2 Objects in Caml 41 method move d new functional_point x d end class bad_functional_point int gt object val x int
133. at Unary negation You can also write e instead of e val float gt float gt float Floating point addition val float gt float gt float Floating point subtraction val float gt float gt float Floating point multiplication val float gt float gt float Floating point division val float gt float gt float Exponentiation val sqrt float gt float Square root val exp float gt float val log float gt float val log10 float gt float Exponential natural logarithm base 10 logarithm val cos float gt float val sin float gt float val tan float gt float val acos float gt float val asin float gt float val atan float gt float val atan2 float gt float gt float The usual trignonmetric functions 200 val val val val val val val val val val val val val val cosh float gt float sinh float gt float tanh float gt float The usual hyperbolic trigonometric functions ceil float gt float floor float gt float Round the given float to an integer value floor f returns the greatest integer value less than or equal to f ceil f returns the least integer value greater than or equal to f abs_float float gt float Return the absolute value of the argument mod_float float gt float gt float mod_float a b returns the remainder of a with respect to b Th
134. ata structures are immutable but a few most notably arrays are mutable meaning that they can be modified in place at any time 1 3 Functions as values Caml is a functional language functions in the full mathematical sense are supported and can be passed around freely just as any other piece of data For instance here is a deriv function that takes any float function as argument and returns an approximation of its derivative function let deriv f dx function x gt f x dx f x dx val deriv float gt float gt float gt float gt float lt fun gt let sin deriv sin 1e 6 val sin float gt float lt fun gt sin pi float 1 00000000014 Even function composition is definable let compose f g function x gt f g x val compose a gt b gt c gt a gt c gt b lt fun gt let cos2 compose square cos val cos2 float gt float lt fun gt Functions that take other functions as arguments are called functionals or higher order functions Functionals are especially useful to provide iterators or similar generic operations over a data structure For instance the standard Caml library provides a List map functional that applies a given function to each element of a list and returns the list of the results 14 List map function n gt n 2 1 0 1 2 3 4 int list 1 3 5 7 9 This functional
135. atagram socket SOCK_RAW Raw socket SOCK_SEQPACKET Sequenced packets socket The type of socket kinds specifying the semantics of communications Chapter 18 The unix library Unix system calls 273 type sockaddr ADDR_UNIX of string ADDR_INET of inet_addr int The type of socket addresses ADDR_UNIX name is a socket address in the Unix domain name is a file name in the file system ADDR_INET addr port is a socket address in the Internet domain addr is the Internet address of the machine and port is the port number val socket socket_domain gt socket_type gt int gt file_descr Create a new socket in the given domain and with the given kind The third argument is the protocol type 0 selects the default protocol for that kind of sockets val socketpair socket_domain gt socket_type gt int gt file_descr file_descr Create a pair of unnamed sockets connected together val accept file_descr gt file_descr sockaddr Accept connections on the given socket The returned descriptor is a socket connected to the client the returned address is the address of the connecting client val bind file_descr gt sockaddr gt unit Bind a socket to an address val connect file_descr gt sockaddr gt unit Connect a socket to an address val listen file_descr gt int gt unit Set up a socket for receiving connection requests The integer argument is the maximal number of pendin
136. atio of ratio The type of numbers Arithmetic operations 281 282 val num gt num gt num val add_num num gt num gt num Addition val minus_num num gt num Unary negation val num gt num gt num val sub_num num gt num gt num Subtraction val num gt num gt num val mult_num num gt num gt num Multiplication val square_num num gt num Squaring val num gt num gt num val div_num num gt num gt num Division val quo_num num gt num gt num val mod_num num gt num gt num Euclidean division quotient and remainder val num gt num gt num val power_num num gt num gt num Exponentiation val is_integer_num num gt bool Test if a number is an integer val integer_num num gt num val floor_num num gt num val round_num num gt num val ceiling num num gt num Approximate a number by an integer floor_num n returns the largest integer smaller or equal to n ceiling_num n returns the smallest integer bigger or equal to n integer_num n returns the integer closest to n In case of ties rounds towards zero round_num n returns the integer closest to n In case of ties rounds off zero Chapter 19 The num library arbitrary precision rational arithmetic val val val val val val val val val val val val val val val val val val val val sign_num num
137. before len characters have been read Raise Invalid_argument really_input if ofs and len do not designate a valid substring of buff val input_byte in_channel gt int Same as input_char but return the 8 bit integer representing the character Raise End_of_file if an end of file was reached Chapter 16 The core library 207 val input_binary_int in_channel gt int Read an integer encoded in binary format from the given input channel See output_binary_int Raise End_of_file if an end of file was reached while reading the integer val input_value in_channel gt a Read the representation of a structured value as produced by output_value and return the corresponding value This function is identical to Marshal from_channel see the description of module Marshal for more information in particular concerning the lack of type safety val seek_in in_channel gt int gt unit seek_in chan pos sets the current reading position to pos for channel chan This works only for regular files On files of other kinds the behavior is unspecified val pos_in in_channel gt int Return the current reading position for the given channel val in_channel_length in_channel gt int Return the total length number of characters of the given channel This works only for regular files On files of other kinds the result is meaningless val close_in in_channel gt unit Close the given channel Anything can happen if any of the fu
138. bit on 64 bit architectures They are unboxed unallocated 15 2 2 Blocks Blocks in the heap are garbage collected and therefore have strict structure constraints Each block includes a header containing the size of the block in words and the tag of the block The tag governs how the contents of the blocks are structured A tag lower than No_scan_tag indicates a structured block containing well formed values which is recursively traversed by the garbage 174 collector A tag greater than or equal to No_scan_tag indicates a raw block whose contents are not scanned by the garbage collector For the benefits of ad hoc polymorphic primitives such as equality and structured input output structured and raw blocks are further classified according to their tags as follows Tag Contents of the block 0 to No_scan_tag 1 A structured block an array of Caml objects Each field is a value Closure_tag A closure representing a functional value The first word is a pointer to a piece of code the remaining words are value containing the environment String_tag A character string Double_tag A double precision floating point number Double_array_tag An array or record of double precision floating point num bers Abstract_tag A block representing an abstract datatype Final_tag A block representing an abstract datatype with a finaliza tion function to be called when the block is deallocated 15 2 3 Point
139. byte representation in the string buff starting at character number ofs and writing at most len characters It returns the number of characters actually written to the string If the byte representation of v does not fit in len characters the exception Failure is raised val from_channel in_channel gt a Marshal from_channel chan reads from channel chan the byte representation of a structured value as produced by one of the Marshal to_ functions and reconstructs and returns the corresponding value 242 val from_string string gt int gt a Marshal from_string buff ofs unmarshals a structured value like Marshal from_channel does except that the byte representation is not read from a channel but taken from the string buff starting at position ofs val header_size int val data_size string gt int gt int val total_size string gt int gt int The bytes representing a marshaled value are composed of a fixed size header and a variable sized data part whose size can be determined from the header Marshal header_size is the size in characters of the header Marshal data_size buff ofs is the size in characters of the data part assuming a valid header is stored in buff starting at position ofs Finally Marshal total_size buff ofs is the total size in characters of the marshaled value Both Marshal data_size and Marshal total_size raise Failure if buff ofs does not contain a valid header To read the
140. c Unit of unit gt unit Call the function with unit argument Set of bool ref Set the reference to true Clear of bool ref Set the reference to false String of string gt unit Call the function with a string argument Int of int gt unit Call the function with an int argument val Rest of string gt unit Stop interpreting keywords and call the function with each remaining argument The concrete type describing the behavior associated with a keyword parse string spec string list gt string gt unit gt string gt unit Arg parse speclist anonfun usage_msg parses the command line speclist is a list of triples key spec doc key is the option keyword it must start with a character spec gives the option type and the function to call when this option is found on the command line doc is a one line description of this option anonfun is called on anonymous arguments The functions in spec and anonfun are called in the same order as their arguments appear on the command line If an error occurs Arg parse exits the program after printing an error message as follows The reason for the error unknown option invalid or missing argument etc usage_msg The list of options each followed by the corresponding doc string For the user to be able to specify anonymous arguments starting with a include for example String anonfun doc in speclist
141. ccording to their size as zero sized blocks small blocks with size less than or equal to Max_young_wosize and large blocks with size greater than Max_young_wosize The constant Max_young_wosize is declared in the include file mlvalues h It is guaranteed to be at least 64 words so that any block with constant size less than or equal to 64 can be assumed to be small For blocks whose size is computed at run time the size must be compared against Max_young_wosize to determine the correct allocation procedure alloc_small n t returns a fresh small block of size n lt Max_young_wosize words with tag t If this block is a structured block i e if t lt No_scan_tag then the fields of the block initially containing garbage must be initialized with legal values using direct assignment to the fields of the block before the next allocation alloc_shr n t returns a fresh block of size n with tag t The size of the block can be greater than Max_young_wosize It can also be smaller but in this case it is more 178 efficient to call alloc_small instead of alloc_shr If this block is a structured block i e if t lt No_scan_tag then the fields of the block initially containing garbage must be initialized with legal values using the initialize function described below before the next allocation 15 4 5 Finalized blocks Blocks with tag Final_tag have an attached C finalization function that is called when the block becomes unr
142. ccur Hence in the example above Aux appears first and Main can refer to it but Aux cannot refer to Main Notice that only top level structures can be mapped to separately compiled files but not func tors nor module types However all module class objects can appear as components of a structure so the solution is to put the functor or module type inside a structure which can then be mapped to a file Chapter 4 Advanced examples with classes and modules Chapter written by Didier R my In this chapter we show some larger examples using objects classes and modules We review many of the object features simultaneously on the example of a bank account We show how modules taken from the standard library can be expressed as classes Lastly we describe a programming pattern know of as virtual types through the example of window managers 4 1 Extended example bank accounts In this section we illustrate most aspects of Object and inheritance by refining debugging and specializing the following initial naive definition of a simple bank account We reuse the module Euro defined at the end of chapter 2 let euro new Euro c val euro float gt Euro c lt fun gt let zero euro 0 val zero Euro c lt obj gt let neg x x times 1 val neg lt times float gt a gt gt a lt fun gt class account object val mutable balance zero method balance balance method
143. color represent a transparent point when drawing the corresponding image all pixels on the screen corresponding to a transparent pixel in the image will not be modified while other points will be set to the color of the corresponding point in the image This allows superimposing an image over an existing background make_image color array array gt image Convert the given color matrix to an image Each sub array represents one horizontal line All sub arrays must have the same length otherwise exception Graphic_failure is raised dump_image image gt color array array Convert an image to a color matrix draw_image image gt int gt int gt unit Draw the given image with lower left corner at the given point get_image int gt int gt int gt int gt image Capture the contents of a rectangle on the screen as an image The parameters are the same as for fill_rect create_image int gt int gt image create_image w h returns a new image w pixels wide and h pixels tall to be used in conjunction with blit_image The initial image contents are random except that no point is transparent blit_image image gt int gt int gt unit blit_image img x y copies screen pixels into the image img modifying img in place The pixels copied are those inside the rectangle with lower left corner at x y and width and height equal to those of the image Pixels that were transparent in img are left unchanged
144. cter c in string s Raise Not_found if c does not occur in s index_from string gt int gt char gt int rindex_from string gt int gt char gt int Same as String index and String rindex but start searching at the character position given as second argument String index s c is equivalent to String index_from s 0 c and String rindex s c to String rindex_from s String length s 1 c Chapter 17 The standard library 253 val val val val val val val contains string gt char gt bool String contains s c tests if character c appears in the string s contains_from string gt int gt char gt bool String contains_from s start c tests if character c appears in the substring of s starting from start to the end of s Raise Invalid_argument if start is not a valid index of s rcontains_from string gt int gt char gt bool String rcontains_from s stop c tests if character c appears in the substring of s starting from the beginning of s to index stop Raise Invalid_argument if stop is not a valid index of s uppercase string gt string Return a copy of the argument with all lowercase letters translated to uppercase including accented letters of the ISO Latin 1 8859 1 character set lowercase string gt string Return a copy of the argument with all uppercase letters translated to lowercase including accented letters of the ISO Latin 1 8859 1 character set capitalize
145. custom below e Arguments ending in o or a are assumed to be C object files and libraries They are passed to the C linker when linking in custom mode see the description of custom below The output of the linking phase is a file containing compiled bytecode that can be executed by the Objective Caml bytecode interpreter the command named ocamlrun If caml out is the name of the file produced by the linking phase the command ocamlrun caml out arg argg 9p executes the compiled code contained in caml out passing it as arguments the character strings arg to arg See chapter 9 for more details On most Unix systems the file produced by the linking phase can be run directly as in caml out arg argo arg The produced file has the executable bit set and it manages to launch the bytecode interpreter by itself 7 2 Options The following command line options are recognized by ocamlc a Build a library cma file with the object files cmo files given on the command line instead of linking them into an executable file The name of the library can be set with the o option The default name is library cma c Compile only Suppress the linking phase of the compilation Source code files are turned into compiled files but no executable file is produced This option is useful to compile modules separately cc ccomp Use ccomp as the C linker called by ocamlc custom and as the C compiler for compiling c source
146. d flush respective default values for outspace and outnewline are out String make n O nand out n O 1 224 val get_all_formatter_output_functions unit gt string gt int gt int gt unit unit gt unit unit gt unit int gt unit Return the current output functions of the pretty printer including line breaking and indentation functions Multiple formatted output type formatter val val val val val val Abstract data type corresponding to a pretty printer and all its machinery Defining new pretty printers permits the output of material in parallel on several channels Parameters of the pretty printer are local to the pretty printer margin maximum indentation limit maximum number of boxes simultaneously opened ellipsis and so on are specific to each pretty printer and may be fixed independently Given an output channel oc a new formatter writing to that channel is obtained by calling formatter_of_out_channel oc Alternatively the make_formatter function allocates a new formatter with explicit output and flushing functions convenient to output material to strings for instance formatter_of_out_channel out_channel gt formatter formatter_of_out_channel oc returns a new formatter that writes to the corresponding channel oc std_formatter formatter The standard formatter used by the formatting functions above It is defined as formatter_of_out_channel
147. d object type is an object type without ellipsis This would constrains the type of self be closed and is thus rejected Indeed the type of self cannot be closed this would prevent any further extension of the class Therefore a type error is generated when the unification of this type with another type would result in a closed object type class c object self method m self c gt c end Characters 36 40 This expression has type lt m a gt but is here used with type c lt gt Self type cannot escape its class This problem can sometimes be avoided by first defining the abbreviation using a class type class type cO object method m cO end class type c0 object method m c0 end class c c0 object self method m self cO gt c0 end class c cO It is also possible to use a virtual class Inheriting from this class simultaneously allows to enforce all methods of c to have the same type as the methods of cO class virtual c0 object method virtual m cO end class virtual c0 object method virtual m cO end class c object self inherit cO method m self c0 gt c0 end class c object method m c0 end 40 One could think of defining the type abbreviation directly type c1 lt m c1 gt type cl lt m cl gt However the abbreviation cO cannot be defined directly in a similar It can only be defined by a class or a classtyped definition One re
148. d precision The second argument is the number to approximate approx_fix uses decimal notation the first argument is the number of digits after the decimal point approx_exp uses scientific exponential notation the first argument is the number of digits in the mantissa num_of_string string gt num Convert a string to a number Coercions between numerical types int_of_num num gt int num_of_int int gt num nat_of_num num gt nat num_of_nat nat gt num num_of_big_int big_int gt num big_int_of_num num gt big_int ratio_of_num num gt ratio num_of_ratio ratio gt num float_of_num num gt float 19 2 Module Arith_status flags that control rational arithmetic val val val val val arith_status unit gt unit Print the current status of the arithmetic flags get_error_when_null_denominator unit gt bool set_error_when_null_denominator bool gt unit Get or set the flag null_denominator When on attempting to create a rational with a null denominator raises an exception When off rationals with null denominators are accepted Initially on get_normalize_ratio unit gt bool set_normalize_ratio bool gt unit Get or set the flag normalize_ratio When on rational numbers are normalized after each operation When off rational numbers are not normalized until printed Initially off Chapter 19 The num library arbitrary precision rational arithmetic 285 val
149. d which takes an argument of the same type as self The class comparable below is a template for classes with a binary method leq of type a gt bool where the type variable a is bound to the type of self Therefore comparable expands to lt leq a gt bool gt as a We see here that the binder as also allows to write recursive types class virtual comparable object _ a method virtual leq a gt bool end class virtual comparable object a method virtual leq a gt bool end We then define a subclass money of comparable The class money simply wraps floats as comparable objects We will extend it below with more operations There is a type constraint on the class parameter x as the primitive lt is a polymorphic comparison function in Objective Caml The inherit clause ensures that the type of objects of this class is an instance of comparable class money x float object inherit comparable val repr x method value repr Chapter 2 Objects in Caml 45 method leq p repr lt p value end class money float gt object a val repr float method leq a gt bool method value float end Note that the type money1 is not a subtype of type comparable as the self type appears in contravariant position in the type of method leq Indeed an object m of class money has a method leq that expects an argument of type money since it accesses its
150. default Under MacOS the name of the temporary directory is given by the environment variable TempFolder if not set temporary files are created in the current directory 17 8 Module Format pretty printing This module implements a pretty printing facility to format text within pretty printing boxes The pretty printer breaks lines at specified break hints and indents lines according to the box structure You may consider this module as providing an extension to the printf facility to provide automatic line breaking The addition of pretty printing annotations to your regular printf formats gives you fancy indentation and line breaks Pretty printing annotations are described below in the documentation of the function fprintf You may also use the explicit box management and printing functions provided by this module This style is more basic but more verbose than the fprintf concise formats Chapter 17 The standard library 219 For instance the sequence open_box print_string x print_space print_int 1 close_box that prints x 1 within a pretty printing box can be abbreviated as printf s i x 1 Rule of thumb for casual users of this library use simple boxes as obtained by open_box 0 use simple break hints as obtained by print_cut that outputs a simple break hint or by print_space that outputs a space indicating a break hint once a box is opened display its material with basic prin
151. deposit x balance lt balance plus x method withdraw x if x leq balance then balance lt balance plus neg x x else zero end class account object val mutable balance Euro c method balance Euro c 57 58 method deposit Euro c gt unit method withdraw Euro c gt Euro c end let c new account in c deposit euro 100 c withdraw euro 50 Euro c lt obj gt We now refine this definition with a method to compute interest class account_with_interests object self inherit account method private interest self deposit self balance times 0 03 end class account_with_interests object val mutable balance Euro c method balance Euro c method deposit Euro c gt unit method private interest unit method withdraw Euro c gt Euro c end We make the method interest private since clearly it should not be called freely from the outside Here it is only made accessible to subclasses that will manage monthly or yearly updates of the account We should soon fix a bug in the current definition the deposit method can be used for with drawing money by depositing negative amounts We can fix this directly class safe_account object inherit account method deposit x if zero leq x then balance lt balance plus x end class safe_account object val mutable balance Euro c method balance Euro c method deposit Euro c gt
152. directories this error can also appear because you haven t specified the directories to look into Fix use the directory directive to add the correct directories to the search path This expression has type t but is used with type fy See section 7 4 Reference to undefined global mod You have neglected to load in memory an implementation for a module with load See section 8 3 above 8 5 Building custom toplevel systems ocamlmktop The ocamlmktop command builds Objective Caml toplevels that contain user code preloaded at start up The ocamlmktop command takes as argument a set of cmo and cma files and links them with the object files that implement the Objective Caml toplevel The typical use is 130 ocamlmktop o mytoplevel foo cmo bar cmo gee cmo This creates the bytecode file mytoplevel containing the Objective Caml toplevel system plus the code from the three cmo files This toplevel is directly executable and is started by mytoplevel This enters a regular toplevel loop except that the code from foo cmo bar cmo and gee cmo is already loaded in memory just as if you had typed load foo cmo load bar cmo load gee cmo on entrance to the toplevel The modules Foo Bar and Gee are not opened though you still have to do open Foo yourself if this is what you wish 8 6 Options The following command line options are recognized by ocamlmktop cclib libname Pass the lLlibname opti
153. ds as returned by time into a date and a time Assumes the local time zone mktime tm gt float tm Convert a date and time specified by the tm argument into a time in seconds as returned by time Also return a normalized copy of the given tm record with the tm_wday tm_yday and tm_isdst fields recomputed from the other fields The tm argument is interpreted in the local time zone alarm int gt int Schedule a SIGALRM signals after the given number of seconds 270 val sleep int gt unit Stop execution for the given number of seconds val times unit gt process_times Return the execution times of the process val utimes string gt float gt float gt unit Set the last access time second arg and last modification time third arg for a file Times are expressed in seconds from 00 00 00 GMT Jan 1 1970 type interval_timer ITIMER_REAL ITIMER_VIRTUAL ITIMER_PROF The three kinds of interval timers ITIMER_REAL decrements in real time and sends the signal SIGALRM when expired ITIMER_VIRTUAL decrements in process virtual time and sends SIGVTALRM when expired ITIMER_PROF for profiling decrements both when the process is running and when the system is running on behalf of the process it sends SIGPROF when expired type interval_timer_status it_interval float Period it_value float Current value of the timer The type describing the status of an interval timer val g
154. e the ocamlc command simply calls the C compiler on that file with the right I option Now here is a sample Caml program test ml that uses the curses module open Curses let main_window initscr in let small_window newwin 10 5 20 10 in mvwaddstr main_window 10 2 Hello mvwaddstr small_window 4 3 world refresh for i 1 to 100000 do done endwin 188 To compile this program run ocamlc c test ml Finally to link everything together ocamlc custom o test test cmo curses o cclib lcurses 15 8 Advanced example with callbacks This section illustrates the callback facilities described in section 15 6 We are going to package some Caml functions in such a way that they can be linked with C code and called from C just like any C functions The Caml functions are defined in the following mod m1 Caml source useful Caml functions File mod ml some let rec fib n if n lt 2 then 1 else fib n 1 fib n 2 let format_result n Printf sprintf Result is d n n Export those two functions to C let _ let _ Callback register fib fib Callback register format_result format_result Here is the C stub code for calling these functions from C File modwrap c wrappers around the Caml functions include lt stdio h gt include lt string h gt include lt caml mlvalues h gt include lt caml callback h gt int fib int n static value fib_closure NULL if
155. e before all cmx files that refer to the unit z Arguments ending in cmxa are taken to be libraries of object code Such a library packs in two files lib cmxa and lib a a set of object files cmx o files Libraries are build with ocamlopt a see the description of the a option below The object files contained in the library are linked as regular cmx files see above in the order specified when the library was built The only difference is that if an object file contained in a library is not referenced anywhere in the program then it is not linked in Arguments ending in c are passed to the C compiler which generates a o object file This object file is linked with the program Arguments ending in o or a are assumed to be C object files and libraries They are linked with the program The output of the linking phase is a regular Unix executable file It does not need ocamlrun to run 10 2 Options The following command line options are recognized by ocamlopt a Build a library cmxa a file with the object files cmx o files given on the command line instead of linking them into an executable file The name of the library can be set with the o option The default name is library cmxa c Compile only Suppress the linking phase of the compilation Source code files are turned into compiled files but no executable file is produced This option is useful to compile modules separately cc ccomp Use ccomp as t
156. e line number optionally followed by a character string the source file name Line number directives are treated as blank characters during lexical analysis 5 2 Values This section describes the kinds of values that are manipulated by Caml Light programs Chapter 5 The Objective Caml language 79 5 2 1 Base values Integer numbers Integer values are integer numbers from 2 to 230 1 that is 1073741824 to 1073741823 The implementation may support a wider range of integer values on 64 bit platforms the current implementation supports integers ranging from 2 to 262 1 Floating point numbers Floating point values are numbers in floating point representation The current implementation uses double precision floating point numbers conforming to the IEEE 754 standard with 53 bits of mantissa and an exponent ranging from 1022 to 1023 Characters Character values are represented as 8 bit integers between 0 and 255 Character codes between 0 and 127 are interpreted following the ASCII standard The current implementation interprets character codes between 128 and 255 following the ISO 8859 1 standard Character strings String values are finite sequences of characters The current implementation supports strings con taining up to 224 6 characters 16777210 characters 5 2 2 Tuples Tuples of values are written v1 Un standing for the n tuple of values v to vn The current implementation sup
157. e module system This chapter introduces the module system of Objective Caml 3 1 Structures A primary motivation for modules is to package together related definitions such as the definitions of a data type and associated operations over that type and enforce a consistent naming scheme for these definitions This avoids running out of names or accidentally confusing names Such a package is called a structure and is introduced by the struct end construct which contains an arbitrary sequence of definitions The structure is usually given a name with the module binding Here is for instance a structure packaging together a type of priority queues and their operations module PrioQueue if lprio lt rprio then Node lprio lelt remove_top left right struct type priority int type a queue Empty Node of priority a a queue a queue let empty Empty let rec insert queue prio elt match queue with Empty gt Node prio elt Empty Empty Node p e left right gt if prio lt p then Node prio elt insert right p e left else Node p e insert right prio elt left exception Queue_is_empty let rec remove_top function Empty gt raise Queue_is_empty Node prio elt left Empty gt left Node prio elt Empty right gt right Node prio elt Node lprio lelt _ _ as left Node rprio relt _ _ as right gt 49 el
158. e number is either an integer a floating point number or the constant Error representing the result of an invalid operation e g a division by zero Enumerated types are a special case of variant types where all alternatives are constants type sign Positive Negative type sign Positive Negative let sign_int n if n gt 0 then Positive else Negative val sign_int int gt sign lt fun gt To define arithmetic operations for the number type we use pattern matching on the two num bers involved Chapter 1 The core language 15 let add_num ni n2 match ni n2 with Int i1 Int i2 gt Check for overflow of integer addition if sign_int i1 sign_int i2 amp amp sign_int il i2 lt gt sign_int il then Float float i1 float i2 else Int i1 i2 Int i1 Float f2 gt Float float i1 f2 Float f1 Int i2 gt Float f1 float i2 Float f1 Float f2 gt Float f1 f2 Error _ gt Error _ Error gt Error val add_num number gt number gt number lt fun gt add_num Int 123 Float 3 14159 number Float 126 14159 The most common usage of variant types is to describe recursive data structures Consider for example the type of binary trees type a btree Empty Node of a a btree a btree type a btree Empty Node of a a btree a btree This definition reads as f
159. e returned value is a n b where n is the quotient a b rounded towards zero to an integer frexp float gt float int frexp f returns the pair of the significant and the exponent of f When f is zero the significant x and the exponent n of f are equal to zero When f is non zero they are defined by f x 2 nandO 5 lt x lt 1 0 ldexp float gt int gt float ldexp x n returns x 2 n modf float gt float float modf f returns the pair of the fractional and integral part of f float int gt float float_of_int int gt float Convert an integer to floating point truncate float gt int int_of_float float gt int Truncate the given floating point number to an integer The result is unspecified if it falls outside the range of representable integers String operations val More string operations are provided in module String string gt string gt string String concatenation Chapter 16 The core library 201 Character operations More character operations are provided in module Char val int_of_char char gt int Return the ASCII code of the argument val char_of_int int gt char Return the character with the given ASCII code Raise Invalid_argument char_of_int if the argument is outside the range 0 255 Unit operations val ignore a gt unit Discard the value of its argument and return For instance ignore f x discards the result
160. e terminal referred to by the given file descriptor The second argument indicates when the status change takes place immediately TCSANOW when all pending output has been transmitted TCSADRAIN or after flushing all input that has been received but not read TCSAFLUSH TCSADRAIN is recommended when changing the output parameters TCSAFLUSH when changing the input parameters val tcsendbreak file_descr gt int gt unit Send a break condition on the given file descriptor The second argument is the duration of the break in 0 1s units 0 means standard duration 0 25s val tcdrain file_descr gt unit Waits until all output written on the given file descriptor has been transmitted type flush_queue TCIFLUSH TCOFLUSH TCIOFLUSH val tcflush file_descr gt flush_queue gt unit Discard data written on the given file descriptor but not yet transmitted or data received but not yet read depending on the second argument TCIFLUSH flushes data received but not read TCOFLUSH flushes data written but not transmitted and TCIOFLUSH flushes both 278 type flow_action TCOOFF TCOON TCIOFF TCION val tcflow file_descr gt flow_action gt unit Suspend or restart reception or transmission of data on the given file descriptor depending on the second argument TCOOFF suspends output TCOON restarts output TCIOFF transmits a STOP character to suspend input and TCION transmits a START character to restart input val
161. e the exact same shape as list expressions with identifier representing unspecified parts of the list As an example here is insertion sort on a list let rec sort lst match lst with 0 gt O head tail gt insert head sort tail and insert elt lst match lst with gt elt head tail gt if elt lt head then elt lst else head insert elt tail HH H HH H H HF OF Chapter 1 The core language 13 5 val sort a list gt a list lt fun gt val insert a gt a list gt a list lt fun gt sort 1 string list a etc is tale told The type inferred for sort a list gt a list means that sort can actually apply to lists of any type and returns a list of the same type The type a is a type variable and stands for any given type The reason why sort can apply to lists of any type is that the comparisons lt etc are polymorphic in Caml they operate between any two values of the same type This makes sort itself polymorphic over all list types sort 6 2 5 3 int list 2 3 5 6 sort 3 14 2 718 float list 2 718 3 14 The sort function above does not modify its input list it builds and returns a new list con taining the same elements as the input list in ascending order There is actually no way in Caml to modify in place a list once it is built we say that lists are immutable data structures Most Caml d
162. eachable and is about to be reclaimed A pointer to the finalization function occupies the first word of the allocated block the remaining words can contain arbitrary raw data but not Caml pointers since Final_tag is greater than No_scan_tag Finalized blocks must be allocated via the alloc_final function alloc_final n f used maz returns a fresh finalized block of size n words with finalization function f The pointer to the finalization function uses the first word the other n 1 are available for your data The two parameters used and maz are used to control the speed of garbage collection when the finalized object contains pointers to out of heap resources Generally speaking the Caml incre mental major collector adjusts its speed relative to the allocation rate of the program The faster the program allocates the harder the GC works in order to reclaim quickly unreachable blocks and avoid having large amount of floating garbage unreferenced objects that the GC has not yet collected Normally the allocation rate is measured by counting the in heap size of allocated blocks However it often happens that finalized objects contain pointers to out of heap memory blocks and other resources such as file descriptors X Windows bitmaps etc For those blocks the in heap size of blocks is not a good measure of the quantity of resources allocated by the program The two arguments used and maz give the GC an idea of how much out of heap
163. ead as a sequence of Objective Caml phrases and executed as per the use directive section 8 2 The outcome of the evaluation is not printed On reaching the end of file the ocaml command exits immediately No commands are read from standard input In script mode the first line of the script is ignored if it starts with Thus it is theoretically possible to make the script itself executable and put as first line usr local bin ocaml thus calling the toplevel system automatically when the script is run However ocam1 itself is a script on most installations of Objective Caml and Unix kernels usually do not handle nested scripts Windows In addition to the text only command ocaml exe which works exactly as under Unix see above a graphical user interface for the toplevel is available under the name ocamlwin exe It should be launched from the Windows file manager or program manager The Terminal windows is split in two panes Phrases are entered and edited in the bottom pane The top pane displays a copy of the input phrases as they are processed by the Caml Light toplevel interspersed with the toplevel responses The Return key sends the contents of the bottom pane to the Caml Light toplevel The Enter key inserts a newline without Chapter 8 The toplevel system ocaml 127 sending the contents of the Input window This can be configured with the Preferences menu item The contents of the input
164. eak command Breakpoints are assigned numbers when set 158 for further reference The most comfortable way to set breakpoints is through the Emacs interface see section 13 10 break Set a breakpoint at the current position in the program execution The current position must be on an event i e neither at the beginning nor at the end of the program break function Set a breakpoint at the beginning of function This works only when the functional value of the identifier function has been computed and assigned to the identifier Hence this command cannot be used at the very beginning of the program execution when all identifiers are still undefined use goto time to advance execution until the functional value is available break module line Set a breakpoint in module module or in the current module if module is not given at the first event of line line break module line column Set a breakpoint in module module or in the current module if module is not given at the event closest to line line column column break module character Set a breakpoint in module module at the event closest to character number character break address Set a breakpoint at the code address address delete breakpoint numbers Delete the specified breakpoints Without argument all breakpoints are deleted after asking for confirmation info breakpoints Print the list of all breakpoints 13 6 The call stack Each time the pro
165. ects compact unit gt unit gc_compaction Perform a full major collection and compact the heap Note that heap compaction is a lengthy operation 230 17 10 Module Genlex a generic lexical analyzer This module implements a simple standard lexical analyzer presented as a function from character streams to token streams It implements roughly the lexical conventions of Caml but is parameterized by the set of keywords of your language type token Kwd of string Ident of string Int of int Float of float String of string Char of char The type of tokens The lexical classes are Int and Float for integer and floating point numbers String for string literals enclosed in double quotes Char for character literals enclosed in single quotes Ident for identifiers either sequences of letters digits underscores and quotes or sequences of operator characters such as etc and Kwd for keywords either identifiers or single special characters such as etc val make_lexer string list gt char Stream t gt token Stream t Construct the lexer function The first argument is the list of keywords An identifier s is returned as Kwd s if s belongs to this list and as Ident s otherwise A special character s is returned as Kwd s if s belongs to this list and cause a lexical error exception Parse_error otherwise Blanks and newlines are skipped Comments delimited by and are skip
166. ed only in case of error See Functional programming using Caml Light for a more gentle introductions to streams and for some examples of their use in writing parsers A more formal presentation of streams and a discussion of alternate semantics can be found in Parsers in ML by Michel Mauny and Daniel de Rauglaudre in the proceedings of the 1992 ACM conference on Lisp and Functional Programming 6 2 Range patterns In patterns Objective Caml recognizes the form c gt d two character literals separated by as shorthand for the pattern 262 Peg Got la ey id where c1 C2 Cn are the characters that occur between c and din the ASCII character set For instance the pattern 0 9 matches all characters that are digits Chapter 6 Language extensions 113 6 3 Assertion checking Objective Caml supports the assert construct to check debugging assertions The expression assert expr evaluates the expression expr and returns if expr evaluates to true Otherwise the exception Assert_failure is raised with the source file name and the location of expr as arguments Assertion checking can be turned off with the noassert compiler option As a special case assert false is reduced to raise Assert_failure which is poly morphic and is not turned off by the noassert option 6 4 Deferred computations The expression lazy expr returns a value v of type Lazy t that encapsulates the computation of expr
167. ed to inst var name by the value of expr Of course this instance variable must have been declared mutable The expression lt inst var name expr inst var name expr gt evaluates to a copy of the current object in which the values of instance variables inst var name inst var name have been replaced by the values of the corresponding expressions expr XPIy Virtual method definition Method specification is written method private virtual method name typexpr It specifies whether the method is public or private and gives its type Constraints on type parameters The construct constraint typexpr typexpr forces the two type expressions to be equals This is typically used to specify type parameters they can be that way be bound to a specified type expression Initializers A class initializer initializer expr specifies an expression that will be evaluated when an object will be created from the class once all the instance variables have been initialized 5 9 3 Class definitions class definition class class binding and class binding class binding virtual type parameters class name pattern class type class expr type parameters ident ident 102 A class definition class class binding and class binding is recursive Each class binding defines a class name that can be used in the whole expression except for inheritance It can also be used for inheritance but only
168. either Some lt value gt for a value or None to specify the end of the stream val of_list a list gt at Return the stream holding the elements of the list in the same order val of_string string gt char t Return the stream of the characters of the string parameter val of_channel in_channel gt char t Return the stream of the characters read from the input channel Stream iterator val iter a gt unit gt a t gt unit Stream iter f s scans the whole stream s applying function f in turn to each stream element encountered Predefined parsers val next at gt a Return the first element of the stream and remove it from the stream Raise Stream Failure if the stream is empty val empty a t gt unit Return if the stream is empty else raise Stream Failure Chapter 17 The standard library 251 Useful functions val peek a t gt a option Return Some of the first element of the stream or None if the stream is empty val junk a t gt unit Remove the first element of the stream possibly unfreezing it before val count a t gt int Return the current count of the stream elements i e the number of the stream elements discarded val npeek int gt at gt a list npeek n returns the list of the n first elements of the stream or all its remaining elements if less than n elements are available 17 27 Module String strin
169. eive ch returns the event consisting in receiving a value from the channel ch The result value of this event is the value received 298 val val val val val val val val always a gt a event always v returns an event that is always ready for synchronization The result value of this event is v choose a event list gt a event choose evl returns the event that is the alternative of all the events in the list evl wrap a event gt a gt b gt b event wrap ev fn returns the event that performs the same communications as ev then applies the post processing function fn on the return value wrap_abort a event gt unit gt unit gt a event wrap_abort ev fn returns the event that performs the same communications as ev but if it is not selected the function fn is called after the synchronization guard unit gt a event gt a event guard fn returns the event that when synchronized computes fn and behaves as the resulting event This allows to compute events with side effects at the time of the synchronization operation sync a event gt a Synchronize on an event offer all the communication possibilities specified in the event to the outside world and block until one of the communications succeed The result value of that communication is returned select a event list gt a Synchronize on an alternative of events
170. el gt out_channel gt a gt Unix sockaddr gt unit Chapter 22 The graphics library The graphics library provides a set of portable drawing primitives Drawing takes place in a separate window that is created when open_graph is called Unix This library is implemented under the X11 windows system Programs that use the graphics library must be linked as follows ocamlc custom other options graphics cma other files cclib lgraphics cclib 1X11 For interactive use of the graphics library do ocamlmktop custom o mytop graphics cma cclib lgraphics cclib 1X11 mytop Here are the graphics mode specifications supported by open_graph on the X11 implementa tion of this library the argument to open_graph has the format display name geometry where display name is the name of the X windows display to connect to and geometry is a standard X windows geometry specification The two components are separated by a space Either can be omitted or both Examples open_graph foo 0 connects to the display foo 0 and creates a window with the default geometry open_graph foo 0 300x100 50 0 connects to the display foo 0 and creates a window 300 pixels wide by 100 pixels tall at location 50 0 open_graph 300x100 50 0 connects to the default display and creates a window 300 pixels wide by 100 pixels tall at location 50 0 open_graph connects to the default display and creates a window with the default geometry
171. ele ds Ba Be ee 57 57 63 69 73 75 75 78 80 83 85 85 87 95 97 103 106 109 111 111 112 113 113 113 113 115 117 117 118 121 121 9 The runtime system ocamlrun 131 OW ONGENICW sc seu aa ake cde ee E e OR Moe Sheen et EG he SO oe Foe eS ee 131 O20 gt OPtONS peip Ret Ake BE Rares A eh hear Ee ee BR Be es Sie ee 131 O 3 Common errors hm aor oe oe Rh go Ed ae ek we ate Be a Ea ee Bd ae 132 10 Native code compilation ocamlopt 135 10 1 Overview of the compiler aooaa aa ee 135 10 2 gt Options x y gts Soe 8 yk Gl EE ke Soar ee ey Ble Oe R RR 136 10 3 Common Errors orrei kes igs Be ae Lea SAE oe Bae ee ee a Se 139 10 4 Compatibility with the bytecode compiler 2 0200 5 139 11 Lexer and parser generators ocamllex ocamlyacc 141 11 1 Overview of ocamllex 0 2 141 11 2 Syntax of lexer definitions 2 2 a 142 TES Ovetview of ocamlyacens wa siea piana a eo Bee poe Ge Ba Aes ES 144 11 4 Syntax of grammar definitions 0 0 00 ee ee 144 TLS A Options au alae ah he alee a p adoa ft Prita wwe ale oh eee aoe 146 11 6 A complete example 0 00 00 ce ee 147 TLT Common errors iis p68 eh ee ke ee ee ee a Pe eee on hve a 148 12 Dependency generator ocamldep 151 TXT e ODO DS aee hx Pe So Se aes Seat eh Svar ae ae a ee Woe ee BR adore eh S 151 122 Ac typical Makefile ccs sar Gate Sgr ee p ata oe ee Sha EE ee Se 151 13 The debugger ocamldebug 15
172. en_process_out open_process and open_process_full respectively wait for the associated command to terminate and return its termination status Symbolic links val symlink string gt string gt unit symlink source dest creates the file dest as a symbolic link to the file source val readlink string gt string Read the contents of a link Polling val select file_descr list gt file_descr list gt file_descr list gt float gt file_descr list file_descr list file_descr list Wait until some input output operations become possible on some channels The three list arguments are respectively a set of descriptors to check for reading first argument for writing second argument or for exceptional conditions third argument The fourth argument is the maximal timeout in seconds a negative fourth argument means no timeout unbounded wait The result is composed of three sets of descriptors those ready for reading first component ready for writing second component and over which an exceptional condition is pending third component 268 Locking type lock_command F_ULOCK Unlock a region F_LOCK Lock a region for writing and block if already locked F_TLOCK Lock a region for writing or fail if already locked F_TEST Test a region for other process locks F_RLOCK Lock a region for reading and block if already locked F_TRLOCK Lock a region for reading or fail if al
173. er gt member x tl end module Set functor Elt ORDERED_TYPE gt sig type element Elt t and set element list val empty a list val add Elt t gt Elt t list gt Elt t list val member Elt t gt Elt t list gt bool end By applying the Set functor to a structure implementing an ordered type we obtain set operations for this type module OrderedString struct type t string let cmp x y if x y then Equal else if x lt y then Less else Greater end module OrderedString sig type t string val cmp a gt a gt comparison end module StringSet Set OrderedString module StringSet sig type element OrderedString t and set element list val empty a list val add OrderedString t gt OrderedString t list gt OrderedString t list val member OrderedString t gt OrderedString t list gt bool end StringSet member bar StringSet add foo StringSet empty Chapter 3 The module system 53 bool false 3 4 Functors and type abstraction As in the PrioQueue example it would be good style to hide the actual implementation of the type set so that users of the structure will not rely on sets being lists and we can switch later to another more efficient representation of sets without breaking their code This can be achieved by restricting Set by a suitable functor signature module type SETFUNCTOR functor Elt ORDERED_TYPE
174. er 111 private 97 99 101 rec see let 99 sig 103 struct 106 107 then see if to see for true 80 try 87 88 92 type 95 102 106 108 val 97 100 103 virtual 97 99 101 102 when 87 89 while 92 with see match try 103 106 113
175. er 1 The core language 23 Sys argv is an array of strings containing the command line parameters Sys argv 1 is thus the first command line parameter The program above is compiled and executed with the following shell commands ocamlc o fib fib ml fib 10 89 fib 20 10946 24 Chapter 2 Objects in Caml Chapter written by J r me Vouillon and Didier R my This chapter gives an overview of the object oriented features of Objective Caml 2 1 Classes and objects The class point has one instance variable x and two methods get_x and move The initial value of the instance variable is 0 The variable x is declared mutable so the method move can change its value class point object val mutable x 0 method get_x x method move d x lt x d end class point object val mutable x int method get_x int method move int gt unit end HH H H We now create a new point p let p new point val p point lt obj gt Note that the type of p is point This is an abbreviation automatically defined by the class definition above It stands for the object type lt get_x int move int gt unit gt listing the methods of class point along with their types Let us apply some methods to p p get_x int 0 p move 3 unit pH get_x int 3 25 26 The evaluation of the body of a class only takes place at object creation time Therefore in the
176. er case the exception is printed on standard error but not propagated back to the parent thread Similarly the result of the application funct arg is discarded and not directly accessible to the parent thread val self unit gt t Return the thread currently executing val id t gt int Return the identifier of the given thread A thread identifier is an integer that identifies uniquely the thread It can be used to build data structures indexed by threads val exit unit gt unit Terminate prematurely the currently executing thread val kill t gt unit Terminate prematurely the thread whose handle is given This functionality is available only with bytecode level threads Chapter 21 The threads library 295 Suspending threads val delay float gt unit delay d suspends the execution of the calling thread for d seconds The other program threads continue to run during this time val join t gt unit join th suspends the execution of the calling thread until the thread th has terminated val wait_read Unix file_descr gt unit val wait_write Unix file_descr gt unit Suspend the execution of the calling thread until at least one character is available for reading wait_read or one character can be written without blocking wait_write on the given Unix file descriptor val wait_timed_read Unix file_descr gt float gt bool val wait_timed_write Unix file_descr gt float gt bool Same as
177. er definition Recursively call the lexer on the given entry point Useful for lexing nested comments for example 11 2 6 Reserved identifiers All identifiers starting with __ocaml_lex are reserved for use by ocamllex do not use any such identifier in your programs 11 3 Overview of ocamlyacc The ocamlyacc command produces a parser from a context free grammar specification with at tached semantic actions in the style of yacc Assuming the input file is grammar mly executing ocamlyacc options grammar mly produces Caml code for a parser in the file grammar m1 and its interface in file grammar mli The generated module defines one parsing function per entry point in the grammar These functions have the same names as the entry points Parsing functions take as arguments a lexical analyzer a function from lexer buffers to tokens and a lexer buffer and return the semantic attribute of the corresponding entry point Lexical analyzer functions are usually generated from a lexer specification by the ocamllex program Lexer buffers are an abstract data type implemented in the standard library module Lexing Tokens are values from the concrete type token defined in the interface file grammar mli produced by ocamlyacc 11 4 Syntax of grammar definitions Grammar definitions have the following format i header ht declarations Ah rules Ah trailer Comments are enclosed between and as in C in the declarations and
178. er directory if their base name is preserved and the correct I options are given to the compiler The compiler will flag an error if it loads a cmi file that has been renamed Compiled bytecode files cmo files on the other hand can be freely renamed once created That s because the linker never attempts to find by itself the cmo file that implements a module with a given name it relies instead on the user providing the list of cmo files by hand 7 4 Common errors This section describes and explains the most frequently encountered error messages Cannot find file filename The named file could not be found in the current directory nor in the directories of the search path The filename is either a compiled interface file cmi file or a compiled bytecode file cmo file If filename has the format mod cmi this means you are trying to compile a file that references identifiers from module mod but you have not yet compiled an interface 122 for module mod Fix compile mod mli or mod ml first to create the compiled interface mod cmi If filename has the format mod cmo this means you are trying to link a bytecode object file that does not exist yet Fix compile mod m1 first If your program spans several directories this error can also appear because you haven t specified the directories to look into Fix add the correct I options to the command line Corrupted compiled interface filename The compiler produces this err
179. er number expr by the value of expr The exception Invalid_argument is raised if the access is out of bounds The value of the whole expression is 5 7 4 Operators Symbols from the class infix symbol1s as well as the keywords or and amp can appear in infix position between two expressions Symbols from the class prefix symbols can appear in prefix position in front of an expression Infix and prefix symbols do not have a fixed meaning they are simply interpreted as applications of functions bound to the names corresponding to the symbols The expression prefix symbol expr is interpreted as the application prefix symbol expr Similarly the expression expr infix symbol exprs is interpreted as the application infix symbol expr expr The table below lists the symbols defined in the initial environment and their initial meaning See the description of the standard library module Pervasive in chapter 16 for more details Their meaning may be changed at any time using let infix op name names 94 Operator Initial meaning Integer addition infix Integer subtraction prefix Integer negation Integer multiplication Integer division Raise Division_by_zero if second argument is zero The result is unspecified if either argument is negative mod Integer modulus Raise Division_by_zero if second argument is zero The result is unspecified if either argument is negative land Bitwise logic
180. eritance in a subclass money3 of money2 the times method would return an object of class money2 but not of class money3 as would be expected The class money could naturally carry another binary method Here is a direct definition class money x object self a val repr x method value repr method print print_float repr method times k lt repr k x gt method leq p a repr lt p value method plus p a lt repr x p value gt end class money float gt object a val repr float method leq a gt bool method plus a gt a method print unit method times float gt a method value float end 2 15 Friends The above class money reveals a problem that often occurs with binary methods In order to interact with other objects of the same class the representation of money objects must be revealed using a method such as value If we remove all binary methods here plus and leq the representation can easily be hidden inside objects by removing the method value as well However this is not possible as long as some binary requires access to the representation on object of the same class but different from self class safe_money x object self a val repr x method print print_float repr method times k lt repr k x gt end class safe_money float gt object a val repr float method print
181. ers it is the same as structural equality On mutable structures e1 e2 is true if and only if physical modification of e1 also affects e2 On non mutable structures the behavior of is implementation dependent except that e1 e2 implies e1 e2 a gt a gt bool Negation of Chapter 16 The core library 197 Boolean operations val not bool gt bool The boolean negation val amp amp bool gt bool gt bool val amp bool gt bool gt bool The boolean and Evaluation is sequential left to right in e1 amp amp e2 e1 is evaluated first and if it returns false e2 is not evaluated at all val I bool gt bool gt bool val or bool gt bool gt bool The boolean or Evaluation is sequential left to right in e1 e2 e1 is evaluated first and if it returns true e2 is not evaluated at all Integer arithmetic Integers are 31 bits wide or 63 bits on 64 bit processors All operations are taken modulo 231 or 263 They do not fail on overflow val int gt int Unary negation You can also write e instead of e val succ int gt int succ x is x 1 val pred int gt int pred x is x 1 val int gt int gt int Integer addition val int gt int gt int Integer subtraction val int gt int gt int Integer multiplication val int gt int gt int Integer division Raise Division_by_zer
182. ers outside the heap Any word aligned pointer to an address outside the heap can be safely cast to and from the type value This includes pointers returned by malloc and pointers to C variables of size at least one word obtained with the amp operator 15 3 Representation of Caml data types This section describes how Caml data types are encoded in the value type 15 3 1 Atomic types Caml type Encoding int Unboxed integer values char Unboxed integer values ASCII code float Blocks with tag Double_tag string Blocks with tag String_tag 15 3 2 Tuples and records Tuples are represented by pointers to blocks with tag 0 Records are also represented by zero tagged blocks The ordering of labels in the record type declaration determines the layout of the record fields the value associated to the label declared first is stored in field 0 of the block the value associated to the label declared next goes in field 1 and so on As an optimization records whose fields all have static type float are represented as arrays of floating point numbers with tag Double_array_tag See the section below on arrays Chapter 15 Interfacing C with Objective Caml 175 15 3 3 Arrays Arrays of integers and pointers are represented like tuples that is as pointers to blocks tagged 0 They are accessed with the Field macro for reading and the modify function for writing Arrays of floating point numbers type float array
183. es Boe bake As oP oe he ie eae So USINGCOCTCIONS fc aTe eek Es te a be Oot ecards poe Gand Bod oA Sore Functional objects s u ene s ae aa a aa ee Cloning objects 20 2 sos a a e ae e Eo aA a a a a a E a ee a Recursive Classes nse k 3 aT aA Boe hd Sate teehee o RT E ot sie eee es Binary methods sase sri digs Bee os He ee BM ie eke BS Gee Se wd ee BY PEETS jib whet SMG lay el G28 Sod os aa epee aoe Made a ah th wath te Deve be edict aly to ate ens Sas th amp module system Structures so wed a eee we See BA ES a ee ee ed eee DISMAGUTES hee pe aata es SG es Ee Ee ee Re ee SP oe Pe ES PINCO 44 5 fea 4e oh see eho Paes Rte Bo heen Ges Be ee a Be OO ces Ey Be Functors and type abstraction o oo ee Modules and separate compilation 2 2 ee 11 11 12 13 14 15 17 18 20 22 25 25 28 28 29 30 31 32 33 34 37 40 41 44 44 46 4 Advanced examples with classes and modules 4 1 4 2 4 3 Extended example bank accounts o o o a a Simple modules as classes 2 we The subject observer pattern oaoa a II The Objective Caml language 5 The Objective Caml language 5 1 5 2 5 3 5 4 5 9 5 6 5 7 5 8 5 9 5 10 5 11 5 12 Lexical conventions oi aana acs Boe ae a a Be es Pee NAICS pa SoBe deh ete te ee a te Rees oth Boi Me tae Brg di a oat Ae Fy ys eo Tag ee Oe Beat Nameg u fe Bk oe 8s Re et hs SC ce ae Hepa ee Bow oe a a A Type expressions ss 40 enie sae wh PE ee a he a ee ES Constants
184. es an array or string outside of its bounds Unix The following environment variables are also consulted LC_CTYPE If set to iso_8859_1 accented characters from the ISO Latin 1 character set in string and character literals are printed as is otherwise they are printed as decimal escape sequences ddd TERM When printing error messages the toplevel system attempts to underline visually the location of the error It consults the TERM variable to determines the type of output terminal and look up its capabilities in the terminal database 128 8 2 Toplevel directives The following directives control the toplevel behavior load files in memory and trace program execution quit Exit the toplevel loop and terminate the ocaml command directory dir name Add the given directory to the list of directories searched for source and compiled files cd dir name Change the current working directory load file name Load in memory a bytecode object file cmo file produced by the batch compiler ocamlc use file name Read compile and execute source phrases from the given file This is textual inclusion phrases are processed just as if they were typed on standard input The reading of the file stops at the first error encountered install_printer printer name This directive registers the function named printer name a value path as a printer for objects whose types match the argument type of the fu
185. es do not match This is the correct behavior even though both set types contain elements of the same type strings both are built upon different orderings of that type and different invariants need to be maintained by the operations being strictly increasing for the standard ordering and for the case insensitive ordering Applying operations from AbstractStringSet to values of type NoCaseStringSet set could give incorrect results or build lists that violate the invariants of NoCaseStringSet 3 5 Modules and separate compilation All examples of modules so far have been given in the context of the interactive system However modules are most useful for large batch compiled programs For these programs it is a practi cal necessity to split the source into several files called compilation units that can be compiled separately thus minimizing recompilation after changes 56 In Objective Caml compilation units are special cases of structures and signatures and the relationship between the units can be explained easily in terms of the module system A compilation unit a comprises two files e the implementation file a m1 which contains a sequence of definitions analogous to the inside of a struct end construct e the interface file a mli which contains a sequence of specifications analogous to the inside of a sig end construct Both files define a structure named A same name as the base name a of the two files with the fir
186. ession associated with the semantic action These functions must be applied to the argument lexbuf which in the code generated by ocamllex is bound to the lexer buffer passed to the parsing function val lexeme lexbuf gt string Lexing lexeme lexbuf returns the string matched by the regular expression val lexeme_char lexbuf gt int gt char Lexing lexeme_char lexbuf i returns character number i in the matched string val lexeme_start lexbuf gt int Lexing lexeme_start lexbuf returns the position in the input stream of the first character of the matched string The first character of the stream has position 0 val lexeme_end lexbuf gt int Lexing lexeme_end lexbuf returns the position in the input stream of the character following the last character of the matched string The first character of the stream has position 0 Chapter 17 The standard library 235 17 14 Module List list operations val val val val val val val val val Some functions are flagged as not tail recursive A tail recursive function uses constant stack space while a non tail recursive function uses stack space proportional to the length of its list argument which can be a problem with very long lists When the function takes several list arguments an approximate formula giving stack usage in unknown units is shown in parentheses The above considerations can usually be ignored if your lists are not longer than about 1
187. ethod bump unit method get_x int method move int gt unit end The annotation virtual here is only used to mentioned a method without providing its definition An alternative definition is class point_again x object self lt move _ gt inherit restricted_point x end class point_again int gt object val mutable x int method bump unit method get_x int method move int gt unit end One could think that a private method should remain private in a subclass However since the method is visible in a subclass it is always possible pick it s code and define a method of the same name that run that code so yet another heavier solution would be class point_again x object self lt move _ gt inherit restricted_point x as super method move super move end class point_again int gt object val mutable x int method bump unit method get_x int method move int gt unit end Of course private methods can also be virtual Then the keywords must appear in this order method private virtual 2 6 Class interfaces Class interfaces are inferred from class definitions They may also be defined directly and used to restrict the type of a class As class declarations they also define a new type constructor 32 class type restricted_point_type object method get_x int method bump unit end class type restricted_point_type
188. ethod may be called from a subclass but only indirectly Instance variable definition The definition val mutable inst var name expr adds an instance variable inst var name whose initial value is the value of expression expr Several variables of the same name can be defined in the same class The flag mutable allows physical modification of this variable by methods An instance variables can only be used in the following methods and initializers of the class Chapter 5 The Objective Caml language 101 Method definition Method definition is written method method name expr The definition of a method overrides any previous definition of this method The method will be public that is not private if any of the definition states so A private method method private method name expr is a method that can only be invoked on self from other methods of the current class as well as of subclasses of the current class This invocation is performed using the expression value name method name where value name is directly bound to self at the beginning of the class definition Private methods do not appear in object types Some special expressions are available in method bodies for manipulating instance variables and duplicating self expr inst var name lt expr lt inst var name expr inst var name expr gt The expression inst var name lt expr modifies in place the current object by replacing the value associat
189. etitimer interval_timer gt interval_timer_status Return the current status of the given interval timer val setitimer interval_timer gt interval_timer_status gt interval_timer_status setitimer t s sets the interval timer t and returns its previous status The s argument is interpreted as follows s it_value if nonzero is the time to the next timer expiration s it_interval if nonzero specifies a value to be used in reloading it_value when the timer expires Setting s it_value to zero disable the timer Setting s it_interval to zero causes the timer to be disabled after its next expiration Chapter 18 The unix library Unix system calls 271 User id group id val val val val val val val getuid unit gt int Return the user id of the user executing the process geteuid unit gt int Return the effective user id under which the process runs setuid int gt unit Set the real user id and effective user id for the process getgid unit gt int Return the group id of the user executing the process getegid unit gt int Return the effective group id under which the process runs setgid int gt unit Set the real group id and effective group id for the process getgroups unit gt int array Return the list of groups to which the user executing the process belongs type passwd_entry pw_name string pw_passwd string pw_uid int pw_gid int pw_gecos string pw
190. eturns the position of the object to the origin class point x_init object val mutable x x_init method get_x x method get_offset x x_init method move d x lt x d end class point int gt object val mutable x int method get_offset int method get_x int method move int gt unit end Expressions can be evaluated and bound before defining the object body of the class This is useful to enforce invariants For instance points can be automatically adjusted to grid as follows class adjusted_point x_init let origin x_init 10 10 in object val mutable x origin method get_x x method get_offset x origin method move d x lt x d end class adjusted_point int gt object val mutable x int method get_offset int method get_x int method move int gt unit end One could also raise an exception if the x_init coordinate is not on the grid In fact the same effect could here be obtained by calling the definition of class point with the value of the origin class adjusted_point x_init point x_init 10 10 class adjusted_point int gt point An alternative solution would have been to define the adjustment in a special allocation function let new_adjusted_point x_init new point x_init 10 10 val new_adjusted_point int gt point lt fun gt 28 However the former pattern is generally more appropriate since
191. exception Error of string let _ Callback register_exception test exception Error any string The C code can then recover the exception identifier using caml_named_value and pass it as first argument to the functions raise_constant raise_with_arg and raise_with_string described in section 15 4 6 to actually raise the exception For example here is a C function that raises the Error exception with the given argument void raise_error char msg raise_with_string caml_named_value test exception msg 15 6 4 Main program in C In normal operation a mixed Caml C program starts by executing the Caml initialization code which then may proceed to call C functions We say that the main program is the Caml code In some applications it is desirable that the C code plays the role of the main program calling Caml functions when needed This can be achieved as follows e The C part of the program must provide a main function which will override the default main function provided by the Caml runtime system Execution will start in the user defined main function just like for a regular C program e At some point the C code must call caml_main argv to initialize the Caml code The argv argument is a C array of strings type char which represents the command line arguments Chapter 15 Interfacing C with Objective Caml 185 as passed as second argument to main The Caml array Sys argv will be initialized from this parameter
192. f the predicate P over D is now satified then Condition signal c Mutex unlock m Chapter 21 The threads library 297 type t The type of condition variables val create unit gt t Return a new condition variable val wait t gt Mutex t gt unit wait c m atomically unlocks the mutex m and suspends the calling process on the condition variable c The process will restart after the condition variable c has been signalled The mutex m is locked again before wait returns val signal t gt unit signal c restarts one of the processes waiting on the condition variable c val broadcast t gt unit broadcast c restarts all processes waiting on the condition variable c 21 4 Module Event first class synchronous communication This module implements synchronous inter thread communications over channels As in John Reppy s Concurrent ML system the communication events are first class values they can be built and combined independently before being offered for communication type a channel The type of communication channels carrying values of type a val new_channel unit gt a channel Return a new channel type a event The type of communication events returning a result of type a val send a channel gt a gt unit event send ch v returns the event consisting in sending the value v over the channel ch The result value of this event is val receive a channel gt a event rec
193. f dump in the current directory The ocamlprof dump file is written only if the program terminates normally by calling exit or by falling through It is not written if the program terminates with an uncaught exception If a compatible dump file already exists in the current directory then the profiling information is accumulated in this dump file This allows for instance the profiling of several executions of a program on different inputs 14 3 Printing profiling information The ocamlprof command produces a source listing of the program modules where execution counts have been inserted as comments For instance ocamlprof foo ml prints the source code for the foo module with comments indicating how many times the functions in this module have been called Naturally this information is accurate only if the source file has not been modified since the profiling execution took place The following options are recognized by ocamlprof f dumpfile Specifies an alternate dump file of profiling information F string Specifies an additional string to be output with profiling information By default ocamlprof will annotate programs with comments of the form n where n is the counter value for a profiling point With option F s the annotation will be sn 14 4 Time profiling Profiling with ocamlprof only records execution counts not the actual time spent into each func tion There is currently no way to perform time profi
194. files cclib lhibname Pass the 1libname option to the C linker when linking in custom runtime mode see the custom option This causes the given C library to be linked with the program Chapter 7 Batch compilation ocamlc 119 ccopt option Pass the given option to the C compiler and linker when linking in custom runtime mode see the custom option For instance ccopt Ldir causes the C linker to search for C libraries in directory dir custom Link in custom runtime mode In the default linking mode the linker produces bytecode that is intended to be executed with the shared runtime system ocamlrun In the custom runtime mode the linker produces an output file that contains both the runtime system and the bytecode for the program The resulting file is larger but it can be executed directly even if the ocamlrun command is not installed Moreover the custom runtime mode enables linking Caml code with user defined C functions as described in chapter 15 g Add debugging information while compiling and linking This option is required in order to be able to debug the program with ocamldebug see chapter 13 i Cause the compiler to print all defined names with their inferred types or their definitions when compiling an implementation m1 file This can be useful to check the types inferred by the compiler Also since the output follows the syntax of interfaces it can help in writing an explicit in
195. following example the instance variable x is initialized to different values for two different objects let xO ref 0 val x0 int ref contents 0 class point object val mutable x incr x0 x0 method get_x x method move d x lt x d end class point object val mutable x int method get_x int method move int gt unit end H HH new point get_x int 1 new point get_x int 2 The class point can also be abstracted over the initial values of points class point fun x_init gt object val mutable x x_init method get_x x method move d x lt x d end class point int gt object val mutable x int method get_x int method move int gt unit end As for declaration of functions the above definition can be abbreviated as class point x_init object val mutable x x_init method get_x x method move d x lt x d end class point int gt object val mutable x int method get_x int method move int gt unit end An instance of the class point is now a function that expects an initial parameter to create a point object new point int gt point lt fun gt let p new point 7 val p point lt obj gt Chapter 2 Objects in Caml 27 The parameter x_init is of course visible in the whole body of the definition including methods For instance the method get_offset in the class below r
196. g fd2 if already opened val set_nonblock file_descr gt unit val clear_nonblock file_descr gt unit Set or clear the non blocking flag on the given descriptor When the non blocking flag is set reading on a descriptor on which there is temporarily no data available raises the EAGAIN or EWOULDBLOCK error instead of blocking writing on a descriptor on which there is temporarily no room for writing also raises EAGAIN or EWOULDBLOCK val set_close_on_exec file_descr gt unit val clear_close_on_exec file_descr gt unit Set or clear the close on exec flag on the given descriptor A descriptor with the close on exec flag is automatically closed when the current process starts another program with one of the exec functions Directories val mkdir string gt file_perm gt unit Create a directory with the given permissions val rmdir string gt unit Remove an empty directory val chdir string gt unit Change the process working directory val getcwd unit gt string Return the name of the current working directory val chroot string gt unit Change the process root directory type dir_handle The type of descriptors over opened directories 266 val opendir string gt dir_handle Open a descriptor on a directory val readdir dir_handle gt string Return the next entry in a directory Raise End_of_file when the end of the directory has been reached val rewinddir dir_handle gt
197. g operations val length string gt int Return the length number of characters of the given string val get string gt int gt char String get s n returns character number n in string s The first character is character number 0 The last character is character number String length s 1 Raise Invalid_argument if n is outside the range 0 to String length s 1 You can also write s n instead of String get s n val set string gt int gt char gt unit String set s n c modifies string s in place replacing the character number n by c Raise Invalid_argument if n is outside the range 0 to String length s 1 You can also write s n lt c instead of String set s n c val create int gt string String create n returns a fresh string of length n The string initially contains arbitrary characters Raise Invalid_argument ifn lt O orn gt Sys max_string_length val make int gt char gt string String make n c returns a fresh string of length n filled with the character c Raise Invalid_argument ifn lt 0 orn gt Sys max_string_length 252 val val val val val val val val val val copy string gt string Return a copy of the given string sub string gt int gt int gt string String sub s start len returns a fresh string of length len containing the characters number start to start len 1 of string s Raise Invalid_argument if start and len do not desi
198. g requests type shutdown_command SHUTDOWN_RECEIVE Close for receiving SHUTDOWN_SEND Close for sending SHUTDOWN_ALL Close both The type of commands for shutdown val shutdown file_descr gt shutdown_command gt unit Shutdown a socket connection SHUTDOWN_SEND as second argument causes reads on the other end of the connection to return an end of file condition SHUTDOWN_RECEIVE causes writes on the other end of the connection to return a closed pipe condition SIGPIPE signal val getsockname file_descr gt sockaddr Return the address of the given socket 274 val getpeername file_descr gt sockaddr Return the address of the host connected to the given socket type msg_flag MSG_OOB MSG_DONTROUTE MSG_PEEK The flags for recv recvfrom send and sendto val recv file_descr gt string gt int gt int gt msg_flag list gt int val recvfrom file_descr gt string gt int gt int gt msg_flag list gt int sockaddr Receive data from an unconnected socket val send file_descr gt string gt int gt int gt msg_flag list gt int val sendto file_descr gt string gt int gt int gt msg_flag list gt sockaddr gt int Send data over an unconnected socket type socket_option SO_DEBUG Record debugging information SO_BROADCAST Permit sending of broadcast messages SOLREUSEADDR Allow reuse of local addresses for bind
199. generalized type variables There are two ways to fix this error e Add a type constraint or a m1i file to give a monomorphic type without type variables to name For instance instead of writing let sort_int_list Sort list lt inferred type a list gt a list with a not generalized write let sort_int_list Sort list lt int list gt int list e If you really need name to have a polymorphic type turn its defining expression into a function by adding an extra parameter For instance instead of writing let map_length List map Array length inferred type a array list gt int list with a not generalized write let map_length lv List map Array length lv Reference to undefined global mod This error appears when trying to link an incomplete or incorrectly ordered set of files Either you have forgotten to provide an implementation for the compilation unit named mod on the command line typically the file named mod cmo or a library containing that file Fix add the missing ml or cmo file to the command line Or you have provided an implementation for the module named mod but it comes too late on the command line the implementation of mod must come before all bytecode object files that reference mod Fix change the order of ml and cmo files on the command line Of course you will always encounter this error if you have mutually recursive functions across modules That is func
200. gin 226 pp_get_max_boxes 226 pp_get_max_indent 226 pp_open_box 226 pp_open_hbox 226 pp_open_hovbox 226 pp_open_hvbox 226 pp_open_tbox 226 pp_open_vbox 226 pp_over_max_boxes 226 pp_print_as 226 pp_print_bool 226 pp_print_break 226 pp_print_char 226 pp_print_cut 226 pp_print_float 226 pp_print_flush 226 pp_print_if_newline 226 pp_print_int 226 pp_print_newline 226 pp_print_space 226 pp_print_string 226 pp_print_tab 226 pp_print_tbreak 226 pp_set_all_formatter_output_functions INDEX TO THE LIBRARY 226 pp_set_ellipsis_text 226 pp_set_formatter_out_channel 226 pp_set_formatter_output_functions 226 pp_set_margin 226 pp_set_max_boxes 226 pp_set_max_indent 226 pp_set_tab 226 pred 197 pred_num 283 prerr_char 203 prerr_endline 203 prerr_float 203 prerr_int 203 prerr_newline 203 prerr_string 203 print 243 print_as 220 print_bool 220 print_break 220 print_char 202 220 print_cut 220 print_endline 202 print_float 202 220 print_flush 220 print_if_newline 221 print_int 202 220 print_newline 202 221 print_space 220 print_stat 229 print_string 202 220 print_tab 222 print_tbreak 222 Printexc module 243 printf 227 244 Printf module 243 push 249 putenv 260 Queue module 244 quo_num 282 quote 288 raise 194 Random module 245 ratio_of_num 284 321 rcontains_from 253 read 262 299 read_float 203 read_int 203 read_key 307 read_line
201. gnate a valid substring of s that is if start lt 0 or len lt 0 or start len gt String length s fill string gt int gt int gt char gt unit String fill s start len c modifies string s in place replacing the characters number start to start len 1 by c Raise Invalid_argument if start and len do not designate a valid substring of s blit string gt int gt string gt int gt int gt unit String blit src srcoff dst dstoff len copies len characters from string src starting at character number srcoff to string dst starting at character number dstoff It works correctly even if src and dst are the same string and the source and destination chunks overlap Raise Invalid_argument if srcoff and len do not designate a valid substring of src or if dstoff and len do not designate a valid substring of dst concat string gt string list gt string String concat sep sl catenates the list of strings s1 inserting the separator string sep between each escaped string gt string Return a copy of the argument with special characters represented by escape sequences following the lexical conventions of Objective Caml index string gt char gt int String index s c returns the position of the leftmost occurrence of character c in string s Raise Not_found if c does not occur in s rindex string gt char gt int String rindex s c returns the position of the rightmost occurrence of chara
202. gnored Sigpipe int Broken pipe sigquit int Interactive termination Sigsegv int Invalid memory reference sigterm int Termination sigusri int Application defined signal 1 sigusr2 int Application defined signal 2 sigchld int Child process terminated sigcont int Continue sigstop int Stop sigtstp int Interactive stop sigttin int Terminal read from background process sigttou int Terminal write from background process sigvtalrm int Timeout in virtual time sigprof int Profiling interrupt Signal numbers for the standard POSIX signals exception Break Exception raised on interactive interrupt if catch_break is on 256 val catch_break bool gt unit catch_break governs whether interactive interrupt ctrl C terminates the program or raises the Break exception Call catch_break true to enable raising Break and catch_break false to let the system terminate the program on user interrupt 17 29 Module Weak arrays of weak pointers type a t The type of arrays of weak pointers weak arrays A weak pointer is an object that the garbage collector may erase at any time A weak pointer is said to be full if it points to an object empty if the object was erased by the GC val create int gt a t Weak create n returns a new weak array of length n All the pointers are initially empty val length a t gt int Wea
203. gram performs a function application it saves the location of the application the return address in a block of data called a stack frame The frame also contains the local variables of the caller function All the frames are allocated in a region of memory called the call stack The command backtrace or bt displays parts of the call stack At any time one of the stack frames is selected by the debugger several debugger commands refer implicitly to the selected frame In particular whenever you ask the debugger for the value of a local variable the value is found in the selected frame The commands frame up and down select whichever frame you are interested in When the program stops the debugger automatically selects the currently executing frame and describes it briefly as the frame command does Chapter 13 The debugger ocamldebug 159 frame Describe the currently selected stack frame frame frame number Select a stack frame by number and describe it The frame currently executing when the program stopped has number 0 its caller has number 1 and so on up the call stack backtrace count bt count Print the call stack This is useful to see which sequence of function calls led to the currently executing frame With a positive argument print only the innermost count frames With a negative argument print only the outermost count frames up count Select and display the stack frame just above the selected frame
204. gt int Return 1 0 or 1 according to the sign of the argument num gt num gt bool lt num gt num gt bool gt num gt num gt bool lt num gt num gt bool gt num gt num gt bool lt gt num gt num gt bool gt num gt bool eq_num num 1lt_num num le_num num gt_num num ge_num num Usual comparisons between numbers compare_num Return 1 O or 1 if the first argument is less than equal to or greater than the second argument max_num num min_num num Return the greater resp the smaller of the two arguments abs_num num gt num gt bool gt num gt bool gt num gt bool gt num gt bool gt num gt num num gt num gt int gt num Absolute value succ_num num succ nis ntl pred_num num pred nis n 1 incr_num num incr ris r r 1 where r is a reference to a number gt num gt num ref gt unit decr_num num ref gt unit decr ris r r 1 where r is a reference to a number Coercions with strings gt num gt num 283 284 val val val val val val val val val val val val val string_of_num num gt string Convert a number to a string using fractional notation approx_num_fix int gt num gt string approx_num_exp int gt num gt string Approximate a number by a decimal The first argument is the require
205. h contains three types of objects plain characters and conversion specifications as specified in the printf module and pretty printing indications The pretty printing indication characters are introduced by a character and their meanings are open a pretty printing box The type and offset of the box may be optionally specified with the following syntax the lt character followed by an optional box type indication then an optional integer offset and the closing gt character Box type is one of h v hv b or hov which stand respectively for an horizontal box a vertical box an horizontal vertical box or an horizontal or vertical box b standing for an horizontal or vertical box demonstrating indentation and hov standing for a regular horizontal or vertical box For instance lt hov 2 gt opens an horizontal or vertical box with indentation 2 close the most recently opened pretty printing box output a good break as with print_cut output a space as with print_space n force a newline as with force_newline output a good break as with print_break The nspaces and offset parameters of the break may be optionally specified with the following syntax the lt character followed by an integer nspaces value then an integer offset and a closing gt character flush the pretty printer as with print_flush flush the pretty printer and output a new line as wi
206. h is then modified in place by replacing the value associated to label in this record by the value of expr This operation is permitted only if label has been declared mutable in the definition of the record type The whole expression expr label lt expr evaluates to the unit value Arrays The expression expr expr evaluates to a n element array whose elements are ini tialized with the values of expr to expr respectively The order in which these expressions are evaluated is unspecified The expression expr expr returns the value of element number expr in the array denoted by expr The first element has number 0 the last element has number n 1 where n is the size of the array The exception Invalid_argument is raised if the access is out of bounds The expression expr exprs lt expr modifies in place the array denoted by expr replac ing element number expr by the value of expr3 The exception Invalid_argument is raised if the access is out of bounds The value of the whole expression is Strings The expression expr exprs returns the value of character number exprs in the string denoted by expr The first character has number 0 the last character has number n 1 where n is the length of the string The exception Invalid_argument is raised if the access is out of bounds The expression expr expryg lt expr modifies in place the string denoted by expry replacing charact
207. h of printing to 1 Useful to browse large data structures without printing them in full display can be abbreviated as d When printing a complex expression a name of the form integer is automatically assigned to its value Such names are also assigned to parts of the value that cannot be printed because the maximal printing depth is exceeded Named values can be printed later on with the commands p integer or d integer Named values are valid only as long as the program is stopped They are forgotten as soon as the program resumes execution set print_depth d Limit the printing of values to a maximal depth of d set print_length Limit the printing of values to at most l nodes printed 13 8 Controlling the debugger 13 8 1 Setting the program name and arguments set program file Set the program name to file set arguments arguments Give arguments as command line arguments for the program A shell is used to pass the arguments to the debugged program You can therefore use wildcards shell variables and file redirections inside the arguments To debug programs that read from standard input it is recommended to redirect their input from a file using set arguments lt input file otherwise input to the program and input to the debugger are not properly separated and inputs are not properly replayed when running the program backwards 13 8 2 How programs are loaded The loadingmode variable controls how the program is executed
208. he C linker called to build the final executable and as the C compiler for compiling c source files cclib llibname Pass the Llibname option to the linker This causes the given C library to be linked with the program ccopt option Pass the given option to the C compiler and linker For instance ccopt Ldir causes the C linker to search for C libraries in directory dir Chapter 10 Native code compilation ocamlopt 137 compact Optimize the produced code for space rather than for time This results in slightly smaller but slightly slower programs The default is to optimize for speed i Cause the compiler to print all defined names with their inferred types or their definitions when compiling an implementation m1 file This can be useful to check the types inferred by the compiler Also since the output follows the syntax of interfaces it can help in writing an explicit interface mli file for a file just redirect the standard output of the compiler to a mli file and edit that file to remove all declarations of unexported names I directory Add the given directory to the list of directories searched for compiled interface files cmi and compiled object code files cmx By default the current directory is searched first then the standard library directory Directories added with I are searched after the current directory in the order in which they were given on the command line but before the standard library
209. he argument the exception Match_failure is raised The other form of function definition is introduced by the keyword fun fun pattern pattern gt expr This expression is equivalent to function pattern gt function pattern gt expr That is the fun expression above evaluates to a curried function with n arguments after applying this function n times to the values v Um the values will be matched in parallel against the patterns pattern pattern If the matching succeeds the function returns the value of expr in an environment enriched by the bindings performed during the matchings If the matching fails the exception Match_failure is raised Guards in pattern matchings Cases of a pattern matching in the function fun match and try constructs can include guard expressions which are arbitrary boolean expressions that must evaluate to true for the match case to be selected Guards occur just before the gt token and are introduced by the when keyword 90 function pattern when cond gt expr pattern when cond gt expr Matching proceeds as described before except that if the value matches some pattern pattern which has a guard cond then the expression cond is evaluated in an environment enriched by the bindings performed during matching If cond evaluates to true then expr is evaluated and its value returned as the result of the matching as usual But if cond evaluates to false the
210. he beginning of the file The file is truncated to zero length if it already exists It is created if it does not already exists Raise Sys_error if the file could not be opened open_out_bin string gt out_channel Same as open_out but the file is opened in binary mode so that no translation takes place during writes On operating systems that do not distinguish between text mode and binary mode this function behaves like open_out open_out_gen open_flag list gt int gt string gt out_channel open_out_gen mode rights filename opens the file named filename for writing as above The extra argument mode specify the opening mode The extra argument rights specifies the file permissions in case the file must be created open_out and open_out_bin are special cases of this function flush out_channel gt unit Flush the buffer associated with the given output channel performing all pending writes on that channel Interactive programs must be careful about flushing standard output and standard error at the right time output_char out_channel gt char gt unit Write the character on the given output channel Chapter 16 The core library 205 val val val val val val val val val val output_string out_channel gt string gt unit Write the string on the given output channel output out_channel gt string gt int gt int gt unit output chan buff ofs len writes len characters
211. he buffer reset t gt unit Empty the buffer and deallocate the internal string holding the buffer contents replacing it with the initial internal string of length n that was allocated by create n For long lived buffers that may have grown a lot reset allows faster reclaimation of the space used by the buffer add_char t gt char gt unit add_char b c appends the character c at the end of the buffer b add_string t gt string gt unit add_string b s appends the string s at the end of the buffer b add_substring t gt string gt int gt int gt unit add_substring b s ofs len takes len characters from offset ofs in string s and appends them at the end of the buffer b add_buffer t gt t gt unit add_buffer b1 b2 appends the current contents of buffer b2 at the end of buffer b1 b2 is not modified add_channel t gt in_channel gt int gt unit add_channel b ic n reads exactly n character from the input channel ic and stores them at the end of buffer b Raise End_of_file if the channel contains fewer than n characters output_buffer out_channel gt t gt unit output_buffer oc b writes the current contents of buffer b on the output channel oc 216 17 4 Module Callback registering Caml values with the C runtime This module allows Caml values to be registered with the C runtime under a symbolic name so that C code can later call back registered Caml functions or raise registered C
212. heck_suffix string gt string gt bool check_suffix name suff returns true if the filename name ends with the suffix suff chop_suffix string gt string gt string chop_suffix name suff removes the suffix suff from the filename name The behavior is undefined if name does not end with the suffix suff chop_extension string gt string Return the given file name without its extension The extension is the shortest suffix starting with a period xyz for instance Raise Invalid_argument if the given name does not contain a period basename string gt string dirname string gt string Split a file name into directory name base file name concat dirname name basename name returns a file name which is equivalent to name Moreover after setting the current directory to dirname name with Sys chdir references to basename name which is a relative file name designate the same file as name before the call to Sys chdir temp_file string gt string gt string temp_file prefix suffix returns the name of a non existent temporary file in the temporary directory The base name of the temporary file is formed by concatenating prefix then a suitably chosen integer number then suffix Under Unix the temporary directory is tmp by default if set the value of the environment variable TMPDIR is used instead Under Windows the name of the temporary directory is the value of the environment variable TEMP or C temp by
213. her the empty string or a string matching regexp regexp regexp Alternative Match any string that matches either regexp or regexp regexp regexp Concatenation Match the concatenation of two strings the first matching regexp the second matching regexps regexp Match the same strings as regexp ident Reference the regular expression bound to ident by an earlier let ident regexp definition Concerning the precedences of operators x and have highest precedence followed by then concatenation then alternation 11 2 5 Actions The actions are arbitrary Caml expressions They are evaluated in a context where the identifier lexbuf is bound to the current lexer buffer Some typical uses for lexbuf in conjunction with the operations on lexer buffers provided by the Lexing standard library module are listed below Lexing lexeme lexbuf Return the matched string Lexing lexeme_char lexbuf n Return the nt character in the matched string The first character corresponds to n 0 144 Lexing lexeme_start lexbuf Return the absolute position in the input text of the beginning of the matched string The first character read from the input text has position 0 Lexing lexeme_end lexbuf Return the absolute position in the input text of the end of the matched string The first character read from the input text has position 0 entrypoint lexbuf Where entrypoint is the name of another entry point in the same lex
214. i files using the extract_cre program installed in the Objective Caml standard library directory val clear_available_units unit gt unit Clear the list of compilation units accessible to dynamically linked programs val allow_unsafe_modules bool gt unit Govern whether unsafe object files are allowed to be dynamically linked A compilation unit is unsafe if it contains declarations of external functions which can break type safety By default dynamic linking of unsafe object files is not allowed type linking_error Undefined_global of string Unavailable_primitive of string type error Not_a_bytecode_file of string Inconsistent_import of string Unavailable_unit of string Unsafe_file Linking_error of string linking error Corrupted_interface of string exception Error of error Errors in dynamic linking are reported by raising the Error exception with a description of the error val error_message error gt string Convert an error description to a printable message Part V Appendix 313 INDEX TO THE LIBRARY Index to the library operator 208 operator 196 amp operator 197 amp amp operator 197 operator 197 operator 199 operator 282 operator 199 operator 282 operator 197 operator 199 operator 282 operator 197 operator 199 operator 282 operator 197 operator 199 operator 282 operator
215. iant type or record type with exactly the constructors or labels specified All users of the structure have access to the constructors or labels and can use them to create or inspect values of that type However users of the structure consider that type as incompatible with any other type a fresh type has been generated Re exported variant type or record type an equation a representation This case combines the previous two the representation of the type is made visible to all users and no fresh type is generated Exception specification The specification exception constr decl in a signature requires the matching structure to provide an exception with the name and arguments specified in the definition and makes the exception available to all users of the structure Chapter 5 The Objective Caml language 105 Class specifications A specification of one or several classes in a signature is written class class spec and class spec and consists of a sequence of mutually recursive definitions of class names Class specifications are described more precisely in section 5 9 4 Class type specifications A specification of one or several classe types in a signature is written class type classtype def and classtype de and consists of a sequence of mutually recursive definitions of class type names Class type specifications are described more precisely in section 5 9 5 Module specifications A specification of a module component in a
216. ic to Unix Windows This is material specific to MS Windows NT and 95 License The Objective Caml system is copyright 1996 1997 1998 Institut National de Recherche en Informatique et en Automatique INRIA INRIA holds all ownership rights to the Objective Caml system See the file LICENSE in the distribution for licensing information The Objective Caml system can be freely redistributed More precisely INRIA grants any user of the Objective Caml system the right to reproduce it provided that the copies are distributed under the conditions given in the LICENSE file The present documentation is distributed under the same conditions 8 Foreword Availability The complete Objective Caml distribution resides on the machine ftp inria fr The distribution files can be transferred by anonymous FTP Host ftp inria fr Internet address 192 93 2 54 Login name anonymous Password your e mail address Directory lang caml light Files see the index in file README More information on the Caml family of languages is also available on the World Wide Web http caml inria fr Part I An introduction to Objective Caml Chapter 1 The core language This part of the manual is a tutorial introduction to the Objective Caml language A good famil iarity with programming in a conventional languages say Pascal or C is assumed but no prior exposure to functional languages is required The present chapter introduces the core la
217. ice 4 Growing and shrinking of the heap 8 Resizing of stacks and memory manager tables 16 Heap compaction 32 Change of GC parameters 64 Computation of major GC slice size l stack_limit The limit in words of the stack size h The initial size of the major heap in words The multiplier is k M or G for multiplication by 2 22 and 2 respectively For example on a 32 bit machine under bash the command export OCAMLRUNPARAM s 256k v 1 tells a subsequent ocamlrun to set its initial minor heap size to 1 megabyte and to print a message at the start of each major GC cycle PATH List of directories searched to find the bytecode executable file 9 3 Common errors This section describes and explains the most frequently encountered error messages filename no such file or directory If filename is the name of a self executable bytecode file this means that either that file does not exist or that it failed to run the ocamlrun bytecode interpreter on itself The second possibility indicates that Objective Caml has not been properly installed on your system Chapter 9 The runtime system ocamlrun 133 Cannot exec camlrun When launching a self executable bytecode file The ocamlrun could not be found in the executable path Check that Objective Caml has been properly installed on your system Cannot find the bytecode file The file that ocamlrun is trying to execute e g the file given as first non option arg
218. if dimx or dimy is less than 1 or greater than Sys max_array_length If the value of e is a floating point number then the maximum size is only Sys max_array_length 2 Array create_matrix is a deprecated alias for Array make_matrix append a array gt a array gt a arra PP y Array append v1 v2 returns a fresh array containing the concatenation of the arrays v1 and v2 concat a array list gt a array Same as Array append but catenates a list of arrays sub a array gt int gt int gt a array Array sub a start len returns a fresh array of length len containing the elements number start to start len 1 of array a Raise Invalid_argument Array sub if start and len do not designate a valid subarray of a that is if start lt 0 or len lt 0 or start len gt Array length a copy a array gt a array Array copy a returns a copy of a that is a fresh array containing the same elements as a fill a array gt int gt int gt a gt unit Array fill a ofs len x modifies the array a in place storing x in elements number ofs to ofs len 1 Raise Invalid_argument Array fill if ofs and len do not designate a valid subarray of a blit a array gt int gt a array gt int gt int gt unit Array blit v1 o1 v2 02 len copies len elements from array v1 starting at element number o1 to array v2 starting at element number o2 It works correctly even if v1 and v
219. ifier at point C c C d command display display value of identifier at point C c C r command run execute the program forward to next breakpoint C c C v command reverse execute the program backward to latest breakpoint C c C 1 command last go back one step in the command history C c C t command backtrace display backtrace of function calls C c C f command finish run forward till the current function returns C c lt command up select the stack frame below the current frame C c gt command down select the stack frame above the current frame In all buffers in Caml editing mode the following debugger commands are also available C x C a C b command break set a breakpoint at event closest to point C x C a C p command print print value of identifier at point C x C a C d command display display value of identifier at point Chapter 14 Profiling ocamlprof This chapter describes how the execution of Objective Caml programs can be profiled by recording how many times functions are called branches of conditionals are taken 14 1 Compiling for profiling Before profiling an execution the program must be compiled in profiling mode using the ocamlcp front end to the ocamlc compiler see chapter 7 When compiling modules separately ocamlcp must be used when compiling the modules production of cmo files and can also be used though this is not strictly necessary when link
220. ilently replaced by the new data remove t gt string gt unit remove db key data removes the data associated with key in db If key has no associated data raise Dbm_error dbm_delete firstkey t gt string nextkey t gt string Enumerate all keys in the given database in an unspecified order firstkey db returns the first key and repeated calls to nextkey db return the remaining keys Not_found is raised when all keys have been enumerated iter string gt string gt a gt t gt unit iter f db applies f to each key data pair in the database db f receives key as first argument and data as second argument Chapter 24 The dynlink library dynamic loading and linking of object files The dynlink library supports type safe dynamic loading and linking of bytecode object files cmo and cma files in a running bytecode program Type safety is ensured by limiting the set of modules from the running program that the loaded object file can access and checking that the running program and the loaded object file have been compiled against the same interfaces for these modules Programs that use the dynlink library simply need to link dynlink cma with their object files and other libraries Linking in custom runtime mode is not necessary Dynamic linking is available only to bytecode programs compiled with ocamlc not to native code programs compiled with ocamlopt 24 1 Module Dynlink dynamic loading
221. imitives are declared in an implementation file or struct end module expression using the external keyword external name type C function name This defines the value name name as a function with type type that executes by calling the given C function For instance here is how the input primitive is declared in the standard library module Pervasives external input in_channel gt string gt int gt int gt int input Primitives with several arguments are always curried The C function does not necessarily have the same name as the ML function External functions thus defined can be specified in interface files or sig end signatures either as regular values val name type thus hiding their implementation as a C function or explicitly as manifest external functions external name type C function name The latter is slightly more efficient as it allows clients of the module to call directly the C function instead of going through the corresponding Caml function The arity number of arguments of a primitive is automatically determined from its Caml type in the external declaration by counting the number of function arrows in the type For instance input above has arity 4 and the input C function is called with four arguments Similarly 169 170 external input2 in_channel string int int gt int input2 has arity 1 and the input2 C function receives one argument which is a quadruple of
222. ind p 1 returns the first element of the list 1 that satisfies the predicate p Raise Not_found if there is no value that satisfies p in the list 1 val filter a gt bool gt a list gt a list val find_all a gt bool gt a list gt a list filter p 1 returns all the elements of the list 1 that satisfies the predicate p The order of the elements in the input list is preserved find_all is another name for filter val partition a gt bool gt a list gt a list a list partition p 1 returns a pair of lists 11 12 where 11 is the list of all the elements of 1 that satisfy the predicate p and 12 is the list of all the elements of 1 that do not satisfy p The order of the elements in the input list is preserved 238 Association lists val assoc a gt a b list gt b assoc a 1 returns the value associated with key a in the list of pairs 1 That is assoc a a b bif a b is the leftmost binding of a in list 1 Raise Not_found if there is no value associated with a in the list 1 val assq a gt a b list gt b Same as assoc but uses physical equality instead of structural equality to compare keys val mem_assoc a gt a b list gt bool Same as assoc but simply return true if a binding exists and false if no bindings exist for the given key val mem_assq a gt a b list gt bool Same as me
223. indow gt int gt int gt unit curses_mvwin external addch char gt unit curses_addch external mvwaddch window gt int gt int gt char gt unit curses_mvwaddch external addstr string gt unit curses_addstr external mvwaddstr window gt int gt int gt string gt unit curses_mvwaddstr lots more omitted To compile this interface ocamlc c curses mli To implement these functions we just have to provide the stub code the core functions are already implemented in the curses library The stub code file curses o looks like include lt curses h gt include lt mlvalues h gt value curses_initscr value unit return value initscr OK to coerce directly from WINDOW to value since that s a block created by malloc Chapter 15 Interfacing C with Objective Caml 187 value curses_wrefresh value win wrefresh WINDOW win return Val_unit value curses_newwin value nlines value ncols value x0 value y0 return value newwin Int_val nlines Int_val ncols Int_val x0 Int_val y0 value curses_addch value c addch Int_val c Characters are encoded like integers return Val_unit value curses_addstr value s addstr String_val s return Val_unit This goes on for pages The file curses c can be compiled with cc c I usr local lib ocaml curses c or even simpler ocamlc c curses c When passed a c fil
224. ing Objective Caml use the with pthread option to configure which also supports native code programs Programs that use this alternate implementation of the threads library must be linked as follows ocamlc thread custom other options threads cma other files cclib lthreads cclib lunix cclib lpthread ocamlopt thread other options threads cmxa other files cclib lthreadsnat cclib lunix cclib lpthread Depending on the operating system extra system libraries can be necessary For instance under Solaris 2 5 add cclib lposix4 at the end of the command line Windows Programs that use the threads library must be linked as follows 293 294 ocamlc thread custom other options threads cma other files cclib lthreads All object files on the command line must also have been compiled with the thread option which selects a special thread safe version of the standard library see chapter 7 21 1 Module Thread lightweight threads type t The type of thread handles Thread creation and termination val create a gt b gt a gt t Thread create funct arg creates a new thread of control in which the function application funct arg is executed concurrently with the other threads of the program The application of Thread create returns the handle of the newly created thread The new thread terminates when the application funct arg returns either normally or by raising an uncaught exception In the latt
225. ing them together To make sure your programs can be compiled in profiling mode avoid using any identifier that begins with __ocaml_prof The amount of profiling information can be controlled through the p option to ocamlcp followed by one or several letters indicating which parts of the program should be profiled a all options f function calls a count point is set at the beginning of function bodies i if then else count points are set in both then branch and else branch 1 while for loops a count point is set at the beginning of the loop body m match branches a count point is set at the beginning of the body of each branch t try with branches a count point is set at the beginning of the body of each branch For instance compiling with ocamlcp p film profiles function calls if then else loops and pattern matching Calling ocamlcp without the p option defaults to p fm meaning that only function calls and pattern matching are profiled Note Due to the implementation of streams and stream patterns as syntactic sugar it is hard to predict what parts of stream expressions and patterns will be profiled by a given flag To profile a program with streams we recommend using ocamlcp p a 165 166 14 2 Profiling an execution Running a bytecode executable file that has been compiled with ocamlcp records the execution counts for the specified parts of the program and saves them in a file called ocamlpro
226. int Parenthesized types The type expression typexpr denotes the same type as typexpr Function types The type expression typexpr gt typexpr2 denotes the type of functions mapping arguments of type typexpr to results of type typexprs 84 Tuple types The type expression typexpr typexpr denotes the type of tuples whose elements belong to types typexpr typexpr respectively Constructed types Type constructors with no parameter as in typeconstr are type expressions The type expression typexpr typeconstr where typeconstr is a type constructor with one pa rameter denotes the application of the unary type constructor typeconstr to the type typexpr The type expression typexpr typexpr typeconstr where typeconstr is a type construc tor with n parameters denotes the application of the n ary type constructor typeconstr to the types typexpr through typexpr Recursive types The type expression typexpr as ident denotes the same type as typexpr and also binds the type variable ident to type typexpr both in typexpr and in the remaining part of the type If the type variable ident actually occurs in typexpr a recursive type is created Recursive types for which there exists a recursive path that does not contain an object type constructor are rejected Object types An object type lt method type method type gt is a record of method types The type lt method type method type
227. ions are not compiled This flag has no effect when linking already compiled files o exec file Specify the name of the output file produced by the linker The default output name is a out in keeping with the Unix tradition If the a option is given specify the name of the library produced If the output obj option is given specify the name of the output file produced output obj Cause the linker to produce a C object file instead of a bytecode executable file This is useful to wrap Caml code as a C library callable from any C program See chapter 15 section 15 6 5 The name of the output object file is camlprog o by default it can be set with the o option pp command Cause the compiler to call the given command as a preprocessor for each source file The output of command is redirected to an intermediate file which is compiled If there are no compilation errors the intermediate file is deleted afterwards The name of this file is built from the basename of the source file with the extension ppi for an interface m1i file and ppo for an implementation m1 file rectypes Allow arbitrary recursive types during type checking By default only recursive types where the recursion goes through an object type are supported thread Compile or link multithreaded programs in combination with the threads library described in chapter 21 What this option actually does is select a special thread safe version of the standard librar
228. ious definitions of a method can be reused by binding the related ancestor Below super is bound to the ancestor printable_point The name super is not actually a variable and can only be used to select a method as in super print 34 object self val c c method color method print print_string super print print_string print_string print_string class printable_colored_point y c c inherit printable_point y as super eG ths We gt self color nyn end class printable_colored_point int gt string gt object val c string val mutable x method color method get_x method move method print end int string int int gt unit unit let p new printable_colored_point 17 red new point at 10 red val p printable_colored_point lt obj gt p print 10 red unit A private method that has been hidden in the parent class is no more visible and is thus not overridden Since initializers are treated as private methods all initializers along the class hierarchy are evaluated in the order they are introduced 2 9 Parameterized classes Reference cells can also be implemented as objects The naive definition fails to typecheck class ref x_init object val mutable x method get x method set y x lt y x_init end Characters 5 106 Some type variables are unbound in this t
229. is value controls the GC messages on standard error output It is a sum of some of the following flags to print messages on the corresponding events Chapter 17 The standard library 229 val val val val val val val val 1 Start of major GC cycle 2 Minor collection and major GC slice 4 Growing and shrinking of the heap 8 Resizing of stacks and memory manager tables 16 Heap compaction 32 Change of GC parameters 64 Computation of major GC slice size Default 0 stack_limit The maximum size of the stack in words This is only relevant to the byte code runtime as the native code runtime uses the operating system s stack Default 256k stat unit gt stat Return the current values of the memory management counters in a stat record print_stat out_channel gt unit Print the current values of the memory management counters in human readable form into the channel argument get unit gt control Return the current values of the GC parameters in a control record set control gt unit set r changes the GC parameters according to the control record r The normal usage is Gc set Gc get with Gc verbose 13 minor unit gt unit Trigger a minor collection major unit gt unit Finish the current major collection cycle full_major unit gt unit Finish the current major collection cycle and perform a complete new cycle This will collect all currently unreachable obj
230. ith the native code compiler ocamlopt 12 1 Options The following command line option is recognized by ocamldep I directory Add the given directory to the list of directories searched for source files If a source file foo ml mentions an external compilation unit Bar a dependency on that unit s interface bar cmi is generated only if the source for bar is found in the current directory or in one of the directories specified with I Otherwise Bar is assumed to be a module form the standard library and no dependencies are generated For programs that span multiple directories it is recommended to pass ocamldep the same I options that are passed to the compiler 12 2 A typical Makefile Here is a template Makefile for a Objective Caml program OCAMLC ocamlc OCAMLOPT ocamlopt OCAMLDEP ocamldep 151 152 INCLUDES all relevant I options here OCAMLFLAGS INCLUDES add other options for ocamlc here OCAMLOPTFLAGS INCLUDES add other options for ocamlopt here progi should be compiled to bytecode and is composed of three units modi mod2 and mod3 The list of object files for progi PROG1_OBJS modi cmo mod2 cmo mod3 cmo progi PROG1_OBJS OCAMLC o prog1 OCAMLFLAGS PROG1_OBJS prog2 should be compiled to native code and is composed of two units mod4 and modbd The list of object files for prog2 PROG2_OBJS mod4 cmx mod5 cmx prog2 PROG2_OBJS OCAMLOPT o prog2 OCAMLFLAGS PROG
231. ition exception constr decl Exception definitions add new constructors to the built in variant type exn of exception values The constructors are declared as for a definition of a variant type 5 9 Classes Classes are defined using a small language similar to the module language 5 9 1 Class types Class types are the class level equivalent of type expressions they specify the general shape and type properties of classes class type class body type typexpr gt class type class body type object typexpr class field spec end class path typexpr typexpr class path class field spec inherit class type val mutable inst var name typexpr method private method name typexpr method private virtual method name typexpr constraint typexpr typexpr Simple class expressions The expression class path is equivalent to the class type bound to the name class path Similarly the expression typexpr typexpr class path is equivalent to the parametric class type 98 bound to the name class path in which type parameters have been instanciated to respectively typexpr typexpr Class function type The class type expression typexpr gt class type is the type of class functions functions from values to classes that take as argument a value of type typexpr and return as result a class of type class type Class body type The class type expression object typexpr class field
232. ition specifies nothing on the type con structor besides its number of parameters its representation is hidden and it is assumed incompatible with any other type Type abbreviation an equation no representation This defines the type constructor as an abbreviation for the type expression on the right of the sign New variant type or record type no equation a representation This generates a new type constructor and defines associated constructors or labels through which values of that type can be directly built or inspected Re exported variant type or record type an equation a representation In this case the type constructor is defined as an abbreviation for the type expression given Chapter 5 The Objective Caml language 97 in the equation but in addition the constructors or labels given in the representation remain attached to the defined type constructor The type expression in the equation part must agree with the representation it must be of the same kind record or variant and have exactly the same constructors or labels in the same order with the same arguments The construct constraint ident typexpr allows to specify type parameters Any actual type argument corresponding to the type parameter ident have to be an instance of typexpr more precisely ident and typexpr are unified Type variables of typexpr can appear in the type equation and the type declaration 5 8 2 Exception definitions exception defin
233. k length ar returns the length number of elements of ar val set a t gt int gt a option gt unit Weak set ar n Some el sets the nth cell of ar to be a full pointer to el Weak set ar n None sets the nth cell of ar to empty Raise Invalid_argument Weak set if n is not in the range 0 to Weak length a 1 val get a t gt int gt a option Weak get ar nreturns None if the nth cell of ar is empty Some x where x is the object if it is full Raise Invalid_argument Weak get ifn is not in the range 0 to Weak length a 1 val check a t gt int gt bool Weak check ar n returns true if the nth cell of ar is full false if it is empty Note that even if Weak check ar n returns true a subsequent Weak get ar n can return None val fill a t gt int gt int gt a option gt unit Weak fill ar ofs len el sets to el all pointers of ar from ofs to ofs len 1 Raise Invalid_argument Weak fill if ofs and len do not designate a valid subarray of a val blit at gt int gt a t gt int gt int gt unit Weak blit ari offi ar2 off2 len copies len weak pointers from ar1 starting at off1 to ar2 starting at off2 It works correctly even if ar1 and ar2 are the same Raise Invalid_argument Weak blit if off1 and len do not designate a valid subarray of ar1 or if of f2 and len do not designate a valid subarray of ar2 Chapter 18 The unix library Unix system call
234. king the head of a list uses an exception to signal the case where an empty list is given exception Empty_list exception Empty_list let head 1 match 1 with gt raise Empty_list hd tl gt hd val head a list gt a lt fun gt head 1 2 int 1 head Uncaught exception Empty_list 18 Exceptions are used throughout the standard library to signal cases where the library functions cannot complete normally For instance the List assoc function which returns the data associ ated with a given key in a list of key data pairs raises the predefined exception Not_found when the key does not appear in the list List assoc 1 0 zero 1 one string one List assoc 2 0 zero 1 one Uncaught exception Not_found Exceptions can be trapped with the try with construct let name_of_binary_digit digit try List assoc digit 0 zero 1 one with Not_found gt not a binary digit val name_of_binary_digit int gt string lt fun gt name_of_binary_digit 0 string zero name_of_binary_digit 1 string not a binary digit The with part is actually a regular pattern matching on the exception value Thus several exceptions can be caught by one try with construct Also finalization can be performed by trapping all exceptions performing the finalization then raising again the excep
235. l from_ functions is given as a but this is misleading the returned Caml value does not possess type a for all a it has one unique type which cannot be determined at compile type The programmer should explicitly give the expected type of the returned value using the following syntax Marshal from_channel chan type Anything can happen at run time if the object in the file does not belong to the given type The representation of marshaled values is not human readable and uses bytes that are not printable characters Therefore input and output channels used in conjunction with Marshal to_channel and Marshal from_channel must be opened in binary mode using e g open_out_bin or open_in_bin channels opened in text mode will cause unmarshaling errors on platforms where text channels behave differently than binary channels e g Windows Chapter 17 The standard library 241 type extern_flags No_sharing Don t preserve sharing Closures Send function closures The flags to the Marshal to_ functions below val to_channel out_channel gt a gt extern_flags list gt unit Marshal to_channel chan v flags writes the representation of v on channel chan The flags argument is a possibly empty list of flags that governs the marshaling behavior with respect to sharing and functional values If flags does not contain Marshal No_sharing circularities and sharing inside the value v are detected and preserved in
236. l lib ocam1 172 15 1 3 Linking C code with Caml code The Objective Caml runtime system comprises three main parts the bytecode interpreter the memory manager and a set of C functions that implement the primitive operations Some bytecode instructions are provided to call these C functions designated by their offset in a table of functions the table of primitives In the default mode the Caml linker produces bytecode for the standard runtime system with a standard set of primitives References to primitives that are not in this standard set result in the unavailable C primitive error In the custom runtime mode the Caml linker scans the object files and determines the set of required primitives Then it builds a suitable runtime system by calling the native code linker with e the table of the required primitives e a library that provides the bytecode interpreter the memory manager and the standard primitives e libraries and object code files 0 files mentioned on the command line for the Caml linker that provide implementations for the user s primitives This builds a runtime system with the required primitives The Caml linker generates bytecode for this custom runtime system The bytecode is appended to the end of the custom runtime system so that it will be automatically executed when the output file custom runtime bytecode is launched To link in custom runtime mode execute the ocamlc comma
237. l match_beginning unit gt int val match_end unit gt int match_beginning returns the position of the first character of the substring that was matched by string_match search_forward or search_backward match_end returns the position of the character following the last character of the matched substring val matched_group int gt string gt string matched_group n s returns the substring of s that was matched by the nth group of the regular expression during the latest string_match search_forward or search_backward The user must make sure that the parameter s is the same string that was passed to the matching or searching function val group_beginning int gt int val group_end int gt int group_beginning n returns the position of the first character of the substring that was matched by the nth group of the regular expression group_end n returns the position of the character following the last character of the matched substring Replacement val global_replace regexp gt string gt string gt string global_replace regexp repl s returns a string identical to s except that all substrings of s that match regexp have been replaced by repl The replacement text repl can contain 1 2 etc these sequences will be replaced by the text matched by the corresponding group in the regular expression O stands for the text matched by the whole regular expression val replace_first regexp gt string gt stri
238. l variables containing values must be registered with the garbage collector using the register_global_root function Registration of a global variable v is achieved by calling register_global_root amp v just before a valid value is stored in v for the first time A registered global variable v can be un registered by calling remove_global_root amp v Note The CAML macros use identifiers local variables type identifiers structure tags that start with caml1__ Do not use any identifier starting with caml__ in your programs 15 5 2 Low level interface We now give the GC rules corresponding to the low level allocation functions alloc_small and alloc_shr You can ignore those rules if you stick to the simplified allocation function alloc Chapter 15 Interfacing C with Objective Caml 181 Rule 5 After a structured block a block with tag less than No_scan_tag is allocated with the low level functions all fields of this block must be filled with well formed values before the next allocation operation If the block has been allocated with alloc_smal1 filling is performed by direct assignment to the fields of the block Field v n wn If the block has been allocated with alloc_shr filling is performed through the initialize function initialize kField v n vn The next allocation can trigger a garbage collection The garbage collector assumes that all structured blocks contain well formed values Newly created blocks contain ra
239. larly it makes the queue type abstract by not providing its actual representation as a concrete type module type PRIOQUEUE sig type priority int still concrete type a queue now abstract val empty a queue val insert a queue gt int gt a gt a queue val extract a queue gt int a a queue exception Queue_is_empty end module type PRIOQUEUE sig type priority int and a queue Chapter 3 The module system 51 val empty a queue val insert a queue gt int gt a gt a queue val extract a queue gt int a a queue exception Queue_is_empty end Restricting the PrioQueue structure by this signature results in another view of the PrioQueue structure where the remove_top function is not accessible and the actual representation of priority queues is hidden module AbstractPrioQueue PrioQueue PRIOQUEUE module AbstractPrioQueue PRIOQUEUE AbstractPrioQueue remove_top Characters 0 28 Unbound value AbstractPrioQueue remove_top AbstractPrioQueue insert AbstractPrioQueue empty 1 hello string AbstractPrioQueue queue lt abstr gt The restriction can also be performed during the definition of the structure as in module PrioQueue struct end PRIOQUEUE An alternate syntax is provided for the above module PrioQueue PRIQQUEUE struct end 3 3 Functors Functors are
240. le c_isig bool Generate signal on INTR QUIT SUSP mutable c_icanon bool Enable canonical processing line buffering and editing mutable c_noflsh bool Disable flush after INTR QUIT SUSP mutable c_echo bool Echo input characters mutable c_echoe bool Echo ERASE to erase previous character mutable c_echok bool Echo KILL to erase the current line mutable c_echonl bool Echo NL even if c_echo is not set Control characters mutable c_vintr char Interrupt character usually ctr1 C mutable c_vquit char Quit character usually ctrl1 mutable c_verase char Erase character usually DEL or ctrl H mutable c_vkill char Kill line character usually ctrl1 U mutable c_veof char End of file character usually ctrl D mutable c_veol char Alternate end of line char usually none mutable c_vmin int Minimum number of characters to read before the read request is satisfied mutable c_vtime int Maximum read wait in 0 1s units mutable c_vstart char Start character usually ctrl1 Q mutable c_vstop char Stop character usually ctr1 S val tcgetattr file_descr gt terminal_io Return the status of the terminal referred to by the given file descriptor type setattr_when TCSANOW TCSADRAIN TCSAFLUSH val tcsetattr file_descr gt setattr_when gt terminal_io gt unit Set the status of th
241. le type open module path 5 11 1 Simple module expressions The expression module path evaluates to the module bound to the name module path The expression module expr evaluates to the same module as module expr The expression module expr module type checks that the type of module expr is a subtype of module type that is that all components specified in module type are implemented in module expr and their implementation meets the requirements given in module type In other terms it checks that the implementation module expr meets the type specification module type The whole expression evaluates to the same module as module expr except that all components not specified in module type are hidden and can no longer be accessed 5 11 2 Structures Structures struct end are collections of definitions for value names type names exceptions module names and module type names The definitions are evaluated in the order in which they appear in the structure The scope of the bindings performed by the definitions extend to the end of the structure As a consequence a definition may refer to names bound by earlier definitions in the same structure For compatibility with toplevel phrases chapter 8 and with Caml Light an optional is allowed after each definition in a structure The has no semantic meaning Also for compatibility expr is allowed as a component of a structure meaning let _ expr i e evaluate expr for its
242. lexers generated by camllex the run time library for parsers generated by camlyacc basic functions over streams parsing of command line arguments registering Caml functions to be called from C operations on file names memory management control and statistics a catch all exception handler system interface 17 1 Module Arg parsing of command line arguments This module provides a general mechanism for extracting options and arguments from the command line to the program Chapter 17 The standard library 211 Syntax of command lines A keyword is a character string starting with a An option is a keyword alone or followed by an argument The types of keywords are Unit Set Clear String Int Float and Rest Unit Set and Clear keywords take no argument String Int and Float keywords take the following word on the command line as an argument A Rest keyword takes the remaining of the command line as string arguments Arguments not preceded by a keyword are called anonymous arguments Examples cmd is assumed to be the command name cmd flag a unit option cmd int 1 an int option with argument 1 cmd string foobar a string option with argument foobar cmd float 12 34 a float option with argument 12 34 cmd abc three anonymous arguments a b and c cmd ab cd two anonymous arguments and a rest option with two arguments Float of float gt unit Call the function with a float argument type spe
243. line 2 xti1 unit print_expr deriv e x print_newline 1 0O0 x 0 unit N Parsing transforming concrete syntax into abstract syntax is usually more delicate Caml offers several tools to help write parsers on the one hand Caml versions of the lexer generator Lex and the parser generator Yacc see chapter 11 which handle LALR 1 languages using push down automata on the other hand a predefined type of streams of characters or tokens and pattern matching over streams which facilitate the writing of recursive descent parsers for LL 1 languages An example using ocamllex and ocamlyacc is given in chapter 11 Here we will use stream parsers open Genlex let lexer make_lexer Eee nyita 4n Wow Wyeth wys val lexer char Stream t gt Genlex token Stream t lt fun gt For the lexical analysis phase transformation of the input text into a stream of tokens we use a generic lexer provided in the standard library module Genlex The make_lexer function takes a list of keywords and returns a lexing function that tokenizes an input stream of characters Tokens are either identifiers keywords or literals integer floats characters strings Whitespace and comments are skipped let token_stream lexer Stream of_string 1 0 x val token_stream Genlex token Stream t lt abstr gt Stream next token_stream Genlex token Float 1 Stream next token_stream
244. ling on bytecode programs generated by ocamlc Native code programs generated by ocamlopt can be profiled for time and execution counts using the p option and the standard Unix profiler gprof Just add the p option when compiling and linking the program ocamlopt o myprog p other options files myprog gprof myprog Caml function names in the output of gprof have the following format Module name_function name_unique number Chapter 14 Profiling ocamlprof 167 Other functions shown are either parts of the Caml run time system or external C functions linked with the program The output of gprof is described in the Unix manual page for gprof 1 It generally consists of two parts a flat profile showing the time spent in each function and the number of invocation of each function and a hierarchical profile based on the call graph Currently only the Intel x86 Linux and Alpha Digital Unix ports of ocamlopt support the two profiles On other platforms gprof will report only the flat profile with just time information When reading the output of gprof keep in mind that the accumulated times computed by gprof are based on heuristics and may not be exact 168 Chapter 15 Interfacing C with Objective Caml This chapter describes how user defined primitives written in C can be linked with Caml code and called from Caml functions 15 1 Overview and compilation information 15 1 1 Declaring primitives User pr
245. ll exception handler Module Printf formatting printing functions 2 Module Queue first in first out queues 2 a a Module Random pseudo random number generator 2 4 Module Set sets over ordered types 1 ee a Module Sort sorting and merging lists 2 2 a Module Stack last in first out stacks 2 a Module Stream streams and parsers 2 2 a Module String string operations soo ee Module Sys system interface 1 ee Module Weak arrays of weak pointers 2 0 2 ee 18 The unix library Unix system calls 18 1 Module Unix interface to the Unix system a oaoa 00 0000 191 193 193 209 210 212 214 216 216 216 217 218 227 230 230 233 233 235 239 240 242 242 243 243 244 245 246 248 248 249 251 253 256 257 19 The num library arbitrary precision rational arithmetic 19 1 Module Num operation on arbitrary precision numbers 19 2 Module Arith_status flags that control rational arithmetic 20 The str library regular expressions and string processing 20 1 Module Str regular expressions and high level string processing 21 The threads library 21 1 Module Thread lightweight threads 2 2 2 ee ee es 21 2 Module Mutex locks for mutual exclusion oaoa 21 3 Module Condition condition variables to synchronize between threads 21 4 Module Event first
246. lue names locally as for the core language expressions Class body The expression object pattern typexpr class field end denotes a class body This is the prototype for an object it lists the instance variables and methods of an objet of this class A class body is a class value it is not evaluated at once Rather its components are evaluated each time an object is created In a class body the pattern pattern typexpr is matched against self therefore provinding a binding for self and self type Self can only be used in method and initializers Self type cannot be a closed object type so that the class remains extensible Inheritance The inheritance construct inherit class expr allows to reuse methods and instance variables from other classes The class expression class expr must evaluate to a class body The instance variables methods and initializers from this class body are added into the current class The addition of a method will override any previously defined methods of the same name An ancestor can be bound by prepending the construct as value name to the inheritance con struct above value name is not a true variable and can only be used to select a method i e in an expression value name method name This gives access to the method method name as it was defined in the parent class even if it is redefined in the current class The scope of an ancestor binding is limited to the current class The ancestor m
247. m_assoc but uses physical equality instead of structural equality to compare keys val remove_assoc a gt a b list gt a b list remove_assoc a 1 returns the list of pairs 1 without the first pair with key a if any Not tail recursive val remove_assq a gt a b list gt a b list Same as remove_assq but uses physical equality instead of structural equality to compare keys Not tail recursive Lists of pairs val split a b list gt a list b list Transform a list of pairs into a pair of lists split ai b1 an bn is fal an b1 bn Not tail recursive val combine a list gt b list gt a b list Transform a pair of lists into a list of pairs combine a1 an b1 bn is al b1 an bn Raise Invalid_argument if the two lists have different lengths Not tail recursive Chapter 17 The standard library 239 17 15 Module Map association tables over ordered types This module implements applicative association tables also known as finite maps or dictionaries given a total ordering function over the keys All operations over maps are purely applicative no side effects The implementation uses balanced binary trees and therefore searching and insertion take time logarithmic in the size of the map module type OrderedType sig type t val compare t gt t gt int end The input signature
248. minal symbol symbol semantic action eee symbol symbol semantic action Rules can also contain the Zprec symbol directive in the right hand side part to override the default precedence and associativity of the rule with the precedence and associativity of the given symbol Semantic actions are arbitrary Caml expressions that are evaluated to produce the semantic attribute attached to the defined nonterminal The semantic actions can access the semantic attributes of the symbols in the right hand side of the rule with the notation 1 is the attribute for the first leftmost symbol 2 is the attribute for the second symbol etc The rules may contain the special symbol error to indicate resynchronization points as in yacc Actions occurring in the middle of rules are not supported 11 4 4 Error handling Error recovery is supported as follows when the parser reaches an error state no grammar rules can apply it calls a function named parse_error with the string syntax error as argument The default parse_error function does nothing and returns thus initiating error recovery see below The user can define a customized parse_error function in the header section of the grammar file The parser also enters error recovery mode if one of the grammar actions raise the Parsing Parse_error exception In error recovery mode the parser discards states from the stack until it reaches a place where the error token can be shif
249. more recent bindings are not passed to f val map a gt b gt gt a t gt bt map f m returns a map with same domain as m where the associated value a of all bindings of m has been replaced by the result of the application of f to a The order in which the associated values are passed to f is unspecified val fold key gt a gt b gt b gt at gt b gt b fold f m a computes f kN dN f ki di a where ki KN are the keys of all bindings in m and d1 dN are the associated data The order in which the bindings are presented to f is unspecified end module Make Ord OrderedType S with type key Ord t Functor building an implementation of the map structure given a totally ordered type 17 16 Module Marshal marshaling of data structures This module provides functions to encode arbitrary data structures as sequences of bytes which can then be written on a file or sent over a pipe or network connection The bytes can then be read back later possibly in another process and decoded back into a data structure The format for the byte sequences is compatible across all machines for a given version of Objective Caml Warning marshaling is currently not type safe The type of marshaled data is not transmitted along the value of the data making it impossible to check that the data read back possesses the type expected by the context In particular the result type of the Marsha
250. mpiler or stored in a C library The caml_startup function must be called from the main C program in order to initialize the Caml runtime and execute the Caml initialization code Just like caml_main it takes one argv parameter containing the command line parameters Unlike caml_main this argv parameter is used only to initialize Sys argv but not for finding the name of the executable file The native code compiler ocamlopt also supports the output obj option causing it to output a C object file containing the native code for all Caml modules on the command line as well as the Caml startup code Initialization is performed by calling caml_startup as in the case of the bytecode compiler For the final linking phase in addition to the object file produced by output obj you will have to provide the Objective Caml runtime library libcamlrun a for bytecode libasmrun a for native code as well as all C libraries that are required by the Caml libraries used For instance assume the Caml part of your program uses the Unix library With ocamlc you should do ocamlc output obj o camlcode o unix cma other cmo and cma files cc o myprog C objects and libraries camlcode o L usr local lib ocaml lunix lcamlrun With ocamlopt you should do ocamlopt output obj o camlcode o unix cmxa other cmx and cmxa files cc o myprog C objects and libraries camlcode o L usr local lib ocaml lunix lasmrun 186 Warning On some ports special
251. n NDBM databases type open_flag Dbm_rdonly Dbm_wronly Dbm_rdwr Dbm_create Flags for opening a database see opendbm 309 310 exception Dbm_error of string val val val val val val val val val Raised by the following functions when an error is encountered opendbm string gt open_flag list gt int gt t Open a descriptor on an NDBM database The first argument is the name of the database without the dir and pag suffixes The second argument is a list of flags Dbm_rdonly opens the database for reading only Dbm_wronly for writing only Dobm_rdwr for reading and writing Dbm_create causes the database to be created if it does not already exist The third argument is the permissions to give to the database files if the database is created close t gt unit Close the given descriptor find t gt string gt string find db key returns the data associated with the given key in the database opened for the descriptor db Raise Not_found if the key has no associated data add t gt string gt string gt unit add db key data inserts the pair key data in the database db If the database already contains data associated with key raise Dbm_error Entry already exists replace t gt string gt string gt unit replace db key data inserts the pair key data in the database db If the database already contains data associated with key that data is discarded and s
252. n a total ordering function over the set elements All operations over sets are purely applicative no side effects The implementation uses balanced binary trees and is therefore reasonably efficient insertion and membership take time logarithmic in the size of the set for instance module type OrderedType sig type t val compare t gt t gt int end The input signature of the functor Set Make t is the type of the set elements compare is a total ordering function over the set elements This is a two argument function f such that f e1 e2 is zero if the elements e1 and e2 are equal f e1 e2 is strictly negative if e1 is smaller than e2 and f e1 e2 is strictly positive if e1 is greater than e2 Example a suitable ordering function is the generic structural comparison function compare module type S sig type elt The type of the set elements type t The type of sets val empty t The empty set val is_empty t gt bool Test whether a set is empty or not Chapter 17 The standard library 247 val mem elt gt t gt bool mem x s tests whether x belongs to the set s val add elt gt t gt t add x s returns a set containing all elements of s plus x If x was already in s s is returned unchanged val singleton elt gt t singleton x returns the one element set containing only x val remove elt gt t gt t remove x s returns a set containing all elements of s except x If x was not in s s is retur
253. n descriptor Operations on file names val unlink string gt unit Removes the named file val rename string gt string gt unit rename old new changes the name of a file from old to new val link string gt string gt unit link source dest creates a hard link named dest to the file named new File permissions and ownership type access_permission R_OK Read permission W_OK Write permission X_OK Execution permission F_OK File exists Flags for the access call val chmod string gt file_perm gt unit Change the permissions of the named file val fchmod file_descr gt file_perm gt unit Change the permissions of an opened file val chown string gt int gt int gt unit Change the owner uid and owner gid of the named file val fchown file_descr gt int gt int gt unit Change the owner uid and owner gid of an opened file val umask int gt int Set the process creation mask and return the previous mask val access string gt access_permission list gt unit Check that the process has the given permissions over the named file Raise Unix_error otherwise Chapter 18 The unix library Unix system calls 265 Operations on file descriptors val dup file_descr gt file_descr Return a new file descriptor referencing the same file as the given descriptor val dup2 file_descr gt file_descr gt unit dup2 fdi fd2 duplicates fd1 to fd2 closin
254. n status The string is interpreted by the shell bin sh and therefore can contain redirections quotes variables etc The result WEXITED 127 indicates that the shell couldn t be executed val getpid unit gt int Return the pid of the process val getppid unit gt int Return the pid of the parent process val nice int gt int Change the process priority The integer argument is added to the nice value Higher values of the nice value mean lower priorities Return the new nice value Basic file input output type file_descr The abstract type of file descriptors val stdin file_descr val stdout file_descr val stderr file_descr File descriptors for standard input standard output and standard error type open_flag O_RDONLY Open for reading O_WRONLY Open for writing O_RDWR Open for reading and writing O_NONBLOCK Open in non blocking mode O_APPEND Open for append O_CREAT Create if nonexistent O_TRUNC Truncate to 0 length if existing O_EXCL Fail if existing The flags to open 262 type file_perm int The type of file access rights val openfile string gt open_flag list gt file_perm gt file_descr Open the named file with the given flags Third argument is the permissions to give to the file if it is created Return a file descriptor on the named file val close file_descr gt unit Close a file descriptor val
255. nce the modules are listed below in alphabetical order of module names For each module the declarations from its signature are printed one by one in typewriter font followed by a short comment All modules and the identifiers they export are indexed at the end of this report Overview Here is a short listing by theme of the standard library modules 209 210 Data structures Char p 216 String p 251 Array p 212 List p 235 Sort p 248 Hashtbl p 230 Random p 245 Set p 246 Map p 239 Oo p 242 Stack p 248 Queue p 244 Buffer p 214 Lazy p 233 Weak p 256 Input output Format p 218 Marshal p 240 Printf p 243 Digest p 216 Parsing Genlex p 230 Lexing p 233 Parsing p 242 Stream p 249 System interface Arg Callback Filename Gc Printexc Sys p 216 217 P P p P P 210 227 243 253 character operations string operations array operations list operations sorting and merging lists hash tables and hash functions pseudo random number generator sets over ordered types association tables over ordered types useful functions on objects last in first out stacks first in first out queues string buffers that grow on demand delayed evaluation references that don t prevent objects from being garbage collected pretty printing marshaling of data structures formatting printing functions MD5 message digest a generic lexer over streams the run time library for
256. nclosing Caml code skipping over the C code That is if a Caml function f calls a C function g that calls back a Caml function h that raises a stray exception then the execution of g is interrupted and the exception is propagated back into f If the C code wishes to catch exceptions escaping the Caml function it can use the func tions callback_exn callback2_exn callback3_exn callbackN_exn These functions take the same arguments as their non _exn counterparts but catch escaping exceptions and return them to the C code The return value v of the callback _exn functions must be tested with the macro Is_exception_result v If the macro returns false no exception occured and v is the value returned by the Caml function If Is_exception_result v returns true an exception escaped and its value the exception descriptor can be recovered using Extract_exception v 15 6 2 Registering Caml closures for use in C functions The main difficulty with the callback functions described above is obtaining a closure to the Caml function to be called For this purpose Objective Caml provides a simple registration mechanism by which Caml code can register Caml functions under some global name and then C code can retrieve the corresponding closure by this global name On the Caml side registration is performed by evaluating Callback register n v Here n is the global name an arbitrary string and v the Caml value For instance let f x p
257. nction That is the toplevel loop will call printer name when it has such an object to print The printing function printer name must use the Format library module to produce its output otherwise its output will not be correctly located in the values printed by the toplevel loop remove_printer printer name Remove the named function from the table of toplevel printers trace function name After executing this directive all calls to the function named function name will be traced That is the argument and the result are displayed for each call as well as the exceptions escaping out of the function raised either by the function itself or by another function it calls If the function is curried each argument is printed as it is passed to the function untrace function name Stop tracing the given function untrace_all Stop tracing all functions traced so far print_depth n Limit the printing of values to a maximal depth of n The parts of values whose depth exceeds n are printed as ellipsis print_length n Limit the number of value nodes printed to at most n Remaining parts of values are printed as ellipsis Chapter 8 The toplevel system ocaml 129 8 3 The toplevel and the module system Toplevel phrases can refer to identifiers defined in compilation units with the same mechanisms as for separately compiled units either by using qualified names Modulename localname or by using the open
258. nctions above is called on a closed channel val set_binary_mode_in in_channel gt bool gt unit set_binary_mode_in ic true sets the channel ic to binary mode no translations take place during input set_binary_mode_out ic false sets the channel ic to text mode depending on the operating system some translations may take place during input For instance under Windows end of lines will be translated from r n to n This function has no effect under operating systems that do not distinguish between text mode and binary mode References type a ref mutable contents a The type of references mutable indirection cells containing a value of type a val ref a gt a ref Return a fresh reference containing the given value 208 val a ref gt a Ir returns the current contents of reference r Equivalent to fun r gt r contents val a ref gt a gt unit r a stores the value of a in reference r Equivalent to fun r v gt r contents lt v val incr int ref gt unit Increment the integer contained in the given reference Equivalent to fun r gt r succ Ir val decr int ref gt unit Decrement the integer contained in the given reference Equivalent to fun r gt r pred r Program termination val exit int gt a Flush all pending writes on stdout and stderr and terminate the process returning the given status code to the operating system us
259. nd with e the custom option e the names of the desired Caml object files cmo and cma files e the names of the C object files and libraries o and a files that implement the required primitives Under Unix a library named libname a residing in one of the standard library directories can also be specified as cclib 1name If you are using the native code compiler ocamlopt the custom flag is not needed as the final linking phase of ocamlopt always builds a standalone executable To build a mixed Caml C executable execute the ocamlopt command with e the names of the desired Caml native object files cmx and cmxa files e the names of the C object files and libraries o and a files that implement the required primitives 15 1 4 Building standalone custom runtime systems It is sometimes inconvenient to build a custom runtime system each time Caml code is linked with C libraries like ocamlc custom does For one thing the building of the runtime system is slow on Chapter 15 Interfacing C with Objective Caml 173 some systems that have bad linkers or slow remote file systems for another thing the platform independence of bytecode files is lost forcing to perform one ocamlc custom link per platform of interest An alternative to ocamlc custom is to build separately a custom runtime system integrating the desired C libraries then generate pure bytecode executables not containing their own run time system
260. nded to clarify the relationship between the names of the modules corre sponding to compilation units and the names of the files that contain their compiled interface and compiled implementation The compiler always derives the module name by taking the capitalized base name of the source file ml or mli file That is it strips the leading directory name if any as well as the m1 or mli suffix then it set the first letter to uppercase in order to comply with the requirement that module names must be capitalized For instance compiling the file mylib misc ml provides an implementation for the module named Misc Other compilation units may refer to components defined in mylib misc ml under the names Misc name they can also do open Misc then use unqualified names name The cmi and cmo files produced by the compiler have the same base name as the source file Hence the compiled files always have their base name equal modulo capitalization of the first letter to the name of the module they describe for cmi files or implement for cmo files When the compiler encounters a reference to a free module identifier Mod it looks in the search path for a file mod cmi note lowercasing of first letter and loads the compiled interface contained in that file As a consequence renaming cmi files is not advised the name of a cmi file must always correspond to the name of the compilation unit it implements It is admissible to move them to anoth
261. ndom data which generally do not represent well formed values If you really need to allocate before the fields can receive their final value first initialize with a constant value e g Val_long 0 then allocate then modify the fields with the correct value see rule 6 Rule 6 Direct assignment to a field of a block as in Field v n w is safe only if v is a block newly allocated by alloc_small that is if no allocation took place between the allocation of v and the assignment to the field In all other cases never assign directly If the block has just been allocated by alloc_shr use initialize to assign a value to a field for the first time initialize kField v n w Otherwise you are updating a field that previously contained a well formed value then call the modify function modify amp Field v n w To illustrate the rules above here is a C function that builds and returns a list containing the two integers given as parameters First we write it using the simplified allocation functions value alloc_list_int int i1 int i2 CAMLparam0 CAMLlocal2 result r r alloc 2 0 Allocate a cons cell Store_field r 0 Val_int i2 car the integer i2 Store_field r 1 Val_int 0 cdr the empty list result alloc 2 0 Allocate the other cons cell Store_field result 0 Val_int il car the integer i1 Store_field result 1 r cdr the first cons cell
262. ne element of the given set or raise Not_found if the set is empty Which element is chosen is unspecified but equal elements will be chosen for equal sets end module Make Ord OrderedType S with type elt Ord t Functor building an implementation of the set structure given a totally ordered type 17 24 Module Sort sorting and merging lists val list a gt a gt bool gt a list gt a list Sort a list in increasing order according to an ordering predicate The predicate should return true if its first argument is less than or equal to its second argument val array a gt a gt bool gt a array gt unit Sort an array in increasing order according to an ordering predicate The predicate should return true if its first argument is less than or equal to its second argument The array is sorted in place val merge a gt a gt bool gt a list gt a list gt a list Merge two lists according to the given predicate Assuming the two argument lists are sorted according to the predicate merge returns a sorted list containing the elements from the two lists The behavior is undefined if the two argument lists were not sorted 17 25 Module Stack last in first out stacks This module implements stacks LIFOs with in place modification type at The type of stacks containing elements of type a exception Empty Raised when pop is applied to an empty stack Chapte
263. ned unchanged val union t gt t gt t val inter t gt t gt t val diff t gt t gt t Union intersection and set difference val compare t gt t gt int Total ordering between sets Can be used as the ordering function for doing sets of sets val equal t gt t gt bool equal s1 s2 tests whether the sets s1 and s2 are equal that is contain equal elements val subset t gt t gt bool subset s1 s2 tests whether the set s1 is a subset of the set s2 val iter elt gt unit gt t gt unit iter f s applies f in turn to all elements of s The order in which the elements of s are presented to f is unspecified val fold elt gt a gt a gt t gt a gt a fold f s a computes f xN f x2 f x1 a where x1 xN are the elements of s The order in which elements of s are presented to f is unspecified val cardinal t gt int Return the number of elements of a set val elements t gt elt list Return the list of all elements of the given set The returned list is sorted in increasing order with respect to the ordering Ord compare where Ord is the argument given to Set Make 248 val min_elt t gt elt Return the smallest element of the given set with respect to the Ord compare ordering or raise Not_found if the set is empty val max_elt t gt elt Same as min_elt but returns the largest element of the given set val choose t gt elt Return o
264. ng gt string Same as global_replace except that only the first substring matching the regular expression is replaced val global_substitute regexp gt string gt string gt string gt string global_substitute regexp subst s returns a string identical to s except that all substrings of s that match regexp have been replaced by the result of function subst The function subst is called once for each matching substring and receives s the whole text as argument 290 val substitute_first regexp gt string gt string gt string gt string Same as global_substitute except that only the first substring matching the regular expression is replaced val replace_matched string gt string gt string replace_matched repl s returns the replacement text repl in which 1 2 etc have been replaced by the text matched by the corresponding groups in the most recent matching operation s must be the same string that was matched during this matching operation Splitting val split regexp gt string gt string list split r s splits s into substrings taking as delimiters the substrings that match r and returns the list of substrings For instance split regexp t s splits s into blank separated words An occurrence of the delimiter at the beginning and at the end of the string is ignored val bounded_split regexp gt string gt int gt string list Same as split but splits into at most n substri
265. ngSet empty 114 Part III The Objective Caml tools 115 Chapter 7 Batch compilation ocamlc This chapter describes the Objective Caml batch compiler ocamlc which compiles Caml source files to bytecode object files and link these object files to produce standalone bytecode executable files These executable files are then run by the bytecode interpreter ocamlrun 7 1 Overview of the compiler The ocamlc command has a command line interface similar to the one of most C compilers It accepts several types of arguments e Arguments ending in mli are taken to be source files for compilation unit interfaces Inter faces specify the names exported by compilation units they declare value names with their types define public data types declare abstract data types and so on From the file z m1i the ocamlc compiler produces a compiled interface in the file x cmi e Arguments ending in ml are taken to be source files for compilation unit implementations Implementations provide definitions for the names exported by the unit and also contain expressions to be evaluated for their side effects From the file x ml the ocamlc compiler produces compiled object bytecode in the file x cmo If the interface file x mli exists the implementation x m1 is checked against the corresponding compiled interface x cmi which is assumed to exist If no interface z mli is provided the compilation of x ml produces a compiled interface file x cmi in
266. ngs where n is the extra integer parameter val split_delim regexp gt string gt string list val bounded_split_delim regexp gt string gt int gt string list Same as split and bounded_split but occurrences of the delimiter at the beginning and at the end of the string are recognized and returned as empty strings in the result For instance split_delim regexp abc returns abc while split with the same arguments returns abc type split_result Text of string Delim of string val full_split regexp gt string gt split_result list val bounded_full_split regexp gt string gt int gt split_result list Same as split_delim and bounded_split_delim but returns the delimiters as well as the substrings contained between delimiters The former are tagged Delim in the result list the latter are tagged Text For instance full_split regexp ab returns Delim Text ab Delim Extracting substrings val string_before string gt int gt string string_before s n returns the substring of all characters of s that precede position n excluding the character at position n Chapter 20 The str library regular expressions and string processing val string_after string gt int gt string string_after s n returns the substring of all characters of s that follow position n including the character at position n val first_chars string gt int gt string first_cha
267. nguage Chapter 2 deals with the object oriented features and chapter 3 with the module system 1 1 Basics For this overview of Caml we use the interactive system which is started by running ocaml1 from the Unix shell or by launching the OCamlwin exe application under Windows This tutorial is presented as the transcript of a session with the interactive system lines starting with represent user input the system responses are printed below without a leading Under the interactive system the user types Caml phrases terminated by in response to the prompt and the system compiles them on the fly executes them and prints the outcome of evaluation Phrases are either simple expressions or let definitions of identifiers either values or functions 1 2 3 int 7 let pi 4 0 atan 1 0 val pi float 3 14159265359 let square x X Xj val square float gt float lt fun gt square sin pi square cos pi float 1 The Caml system computes both the value and the type for each phrase Even function parameters need no explicit type declaration the system infers their types from their usage in the function Notice also that integers and floating point numbers are distinct types with distinct operators and operate on integers but and operate on floats 1 0 2 Characters 0 3 This expression has type float but is here used with type int 11 12 Recursive functio
268. nnel 217 Char module 216 char_of_int 201 chdir 254 265 check 256 check_suffix 218 chmod 264 choose 298 chop_extension 218 chop_suffix 218 chown 264 chr 216 chroot 265 clear 215 231 245 249 clear_available_units 312 clear_close_on_exec 265 clear_graph 302 clear_nonblock 265 clear_parser 243 close 262 310 close_box 219 close_graph 302 close_in 207 close_out 205 close_process 267 close_process_full 267 close_process_in 267 close_process_out 267 close_tbox 222 closedir 266 code 216 combine 238 command 254 compact 229 compare 196 compare_num 283 concat 213 217 235 252 Condition module 296 connect 273 300 contains 253 contains_from 253 contents 215 copy 213 242 252 cos 199 cosh 200 count 251 create 212 214 231 245 249 251 256 294 296 297 create_image 306 create_matrix 213 create_process 266 create_process_env 266 current 212 current_dir_name 217 current_point 304 cyan 303 data_size 242 Dbm module 309 Dbm_error exception 310 decr 208 decr_num 283 delay 295 descr_of_in_channel 262 descr_of_out_channel 262 Digest module 216 dirname 218 div_num 282 Division_by_zero exception 195 draw_arc 304 draw_char 305 draw_circle 304 draw_ellipse 304 draw_image 306 INDEX TO THE LIBRARY draw_string 305 dump_image 306 dup 265 dup2 265 Dynlink module 311 empty 250 Empty exception 245 24
269. nnel This works only for regular files On files of other kinds the result is meaningless close_out out_channel gt unit Close the given channel flushing all buffered write operations The behavior is unspecified if any of the functions above is called on a closed channel set_binary_mode_out out_channel gt bool gt unit set_binary_mode_out oc true sets the channel oc to binary mode no translations take place during output set_binary_mode_out oc false sets the channel oc to text mode depending on the operating system some translations may take place during output For instance under Windows end of lines will be translated from n to r n This function has no effect under operating systems that do not distinguish between text mode and binary mode 206 General input functions val val val val val val val open_in string gt in_channel Open the named file for reading and return a new input channel on that file positionned at the beginning of the file Raise Sys_error if the file could not be opened open_in_bin string gt in_channel Same as open_in but the file is opened in binary mode so that no translation takes place during reads On operating systems that do not distinguish between text mode and binary mode this function behaves like open_in open_in_gen open_flag list gt int gt string gt in_channel open_in_gen mode rights filename opens the file named filename for
270. ns are defined with the let rec binding let rec fib n if n lt 2 then 1 else fib n 1 fib n 2 val fib int gt int lt fun gt fib 10 int 89 1 2 Data types In addition to integers and floating point numbers Caml offers the usual basic data types booleans characters and character strings 1 lt 2 false bool false as char a Hello world string Hello world Predefined data structures include tuples arrays and lists General mechanisms for defining your own data structures are also provided They will be covered in more details later for now we concentrate on lists Lists are either given in extension as a bracketed list of semicolon separated elements or built from the empty list pronounce nil by adding elements in front using the cons operator let 1 is a tale told etc val 1 string list is a tale told etc Life 1 string list Life is a tale told etc As with all other Caml data structures lists do not need to be explicitly allocated and deallocated from memory all memory management is entirely automatic in Caml Similarly there is no explicit handling of pointers the Caml compiler silently introduces pointers where necessary As with most Caml data structures inspecting and destructuring lists is performed by pattern matching List patterns hav
271. o contain simple functor applications as in the syntactic class extended module path above in case the defining module is the result of a functor application Instance variable names and method names need not be qualified the former are local to a class while the latter are global labels Chapter 5 The Objective Caml language 5 4 Type expressions typexpr ident typexpr typeconstr lt he gt class path method type method name typexpr gt typexpr typexpr typexpr typexpr typeconstr typexpr typexpr typeconstr typexpr as ident 83 lt method type method type gt typexpr class path typexpr typexpr class path typexpr The table below shows the relative precedences and associativity of operators and non closed type constructions The constructions with higher precedences come first Operator Associativity Type constructor application gt right as z Type expressions denote types in definitions of data types as well as in type constraints over patterns and expressions Type variables The type expression ident stands for the type variable named ident The type expression _ stands for an anonymous type variable In data type definitions type variables are names for the data type parameters In type constraints they represent unspecified types that can be instantiated by any type to satisfy the type constra
272. o if the second argument is 0 198 val mod int gt int gt int Integer remainder If x gt 0 and y gt 0 the result of x mod y satisfies the following properties 0 lt x mod y lt yand x x y y x mod y Ify 0 x mod y raises Division_by_zero If x lt O or y lt 0 the result of x mod y is not specified and depends on the platform val abs int gt int Return the absolute value of the argument val max_int int val min_int int The greatest and smallest representable integers Bitwise operations val land int gt int gt int Bitwise logical and val lor int gt int gt int Bitwise logical or val lxor int gt int gt int Bitwise logical exclusive or val lnot int gt int Bitwise logical negation val 1sl int gt int gt int n ls1 m shifts n to the left by m bits val lsr int gt int gt int n lsr m shifts n to the right by m bits This is a logical shift zeroes are inserted regardless of the sign of n val asr int gt int gt int n asr m shifts n to the right by m bits This is an arithmetic shift the sign bit of n is replicated Chapter 16 The core library 199 Floating point arithmetic On most platforms Caml s floating point numbers follow the IEEE 754 standard using double precision 64 bits numbers Floating point operations do not fail on overflow or underflow but return denormal numbers val float gt flo
273. object self mytype val mutable copy None method save copy lt Some lt gt method restore match copy with Some x gt x None gt self method clear copy lt None HH H HF end class backup object a val mutable copy a option method clear unit method restore a method save unit end class a backup_ref x object inherit a ref x inherit backup end class a backup_ref 2a gt object b val mutable copy b option val mutable x a method clear unit method get a method restore b method save unit method set a gt unit end let p new backup_ref O in p save p set 1 p save p set 2 get p 0 get p 1 get p 2 get p 3 get p 4 int list 2 1 0 0 0J 44 2 13 Recursive classes Recursive classes can be used to define objects whose types are mutually recursive class window object val mutable top_widget None widget option method top_widget top_widget end and widget w window object val window w method window window end class window object val mutable top_widget widget option method top_widget widget option end class widget window gt object val window window method window window end Although their types are mutually recursive the classes widget and window are themselves inde pendent 2 14 Binary methods A binary method is a metho
274. ock refers to the object class and associated method suite in a format that cannot easily be exploited from C The remaining fields of the object contain the values of the instance variables of the object Instance variables are stored in the order in which they appear in the class definition taking inherited classes into account 15 4 Operations on values 15 4 1 Kind tests e Is_long v is true if value v is an immediate integer false otherwise e Is_block v is true if value v is a pointer to a block and false if it is an immediate integer 176 15 4 2 Operations on integers Val_long returns the value encoding the long int l Long_val v returns the long int encoded in value v Val_int i returns the value encoding the int i Int_val v returns the int encoded in value v Val_bool xz returns the Caml boolean representing the truth value of the C integer z Bool_val v returns 0 if v is the Caml boolean false 1 if vis true Val_true Val_false represent the Caml booleans true and false 15 4 3 Accessing blocks Wosize_val v returns the size of the block v in words excluding the header Tag_val v returns the tag of the block v Field v n returns the value contained in the nt field of the structured block v Fields are numbered from 0 to Wosize_val v 1 Store_field b n v stores the value v in the field number n of value b which must be a structured block Code_val v returns the code part of the clos
275. oints can only be set at events Thus events play the role of line numbers in debuggers for conventional languages During program execution a counter is incremented at each event encountered The value of this counter is referred as the current time Thanks to reverse execution it is possible to jump back and forth to any time of the execution Here is where the debugger events written bowtie are located in the source code e Following a function application arg bowtie e On entrance to a function fun x y z gt bowtie e On each case of a pattern matching definition function match with construct try with construct function pati gt bowtie expr1 ies patN gt bowtie exprN e Between subexpressions of a sequence 156 expri bowtie expr2 bowtie bowtie exprN e In the two branches of a conditional expression if cond then bowtie expri else bowtie expr2 e At the beginning of each iteration of a loop while cond do bowtie body done for i a to b do bowtie body done Exceptions A function application followed by a function return is replaced by the compiler by a jump tail call optimization In this case no event is put after the function application 13 4 2 Starting the debugged program The debugger starts executing the debugged program only when needed This allows setting brea points or assigning debugger variables before execution starts There are several ways to start execution run
276. ollow a binary tree containing values of type a an arbitrary type is either empty or is a node containing one value of type a and two subtrees containing also values of type a that is two a btree Operations on binary trees are naturally expressed as recursive functions following the same structure as the type definition itself For instance here are functions performing lookup and insertion in ordered binary trees elements increase from left to right let rec member x btree match btree with Empty gt false Node y left right gt if x y then true else if x lt y then member x left else member x right val member a gt a btree gt bool lt fun gt let rec insert x btree match btree with Empty gt Node x Empty Empty Node y left right gt if x lt y then Node y insert x left right else Node y left insert x right val insert a gt a btree gt a btree lt fun gt 1 5 Imperative features 16 Though all examples so far were written in purely applicative style Caml is also equipped with full imperative features This includes the usual while and for loops as well as mutable data structures such as arrays Arrays are either given in extension between and brackets or allocated and initialized with the Array create function then filled up later by assignments For instance the function below sums two vectors repre
277. on cd directory Set the working directory for camldebug to directory pwd Print the working directory for camldebug 13 8 5 Turning reverse execution on and off In some cases you may want to turn reverse execution off This speeds up the program execution and is also sometimes useful for interactive programs Normally the debugger takes checkpoints of the program state from time to time That is it makes a copy of the current state of the program using the Unix system call fork If the variable checkpoints is set to off the debugger will not take any checkpoints set checkpoints on off Select whether the debugger makes checkpoints or not 13 8 6 Communication between the debugger and the program The debugger communicate with the program being debugged through a Unix socket You may need to change the socket name for example if you need to run the debugger on a machine and your program on another set socket socket Use socket for communication with the program socket can be either a file name or an Internet port specification host port where host is a host name or an Internet address in dot notation and port is a port number on the host 162 On the debugged program side the socket name is passed either by the D command line option to camlrun or through the CAML_DEBUG_SOCKET environment variable 13 8 7 Fine tuning the debugger Several variables enables to fine tune the debugger Reasonable defaults are provided
278. on 195 is_implicit 217 is_integer_num 282 is_relative 217 iter 214 231 236 245 249 250 310 iter2 236 iteri 214 join 295 junk 251 key_pressed 307 kill 268 294 INDEX TO THE LIBRARY land operator 198 last_chars 291 Lazy module 113 233 ldexp 200 le_num 283 length 212 215 235 245 249 251 256 lexeme 234 lexeme_char 234 lexeme_end 234 lexeme_start 234 Lexing module 233 lineto 304 link 264 list 248 List module 235 listen 273 lnot 198 loadfile 311 loadfile_private 311 localtime 269 lock 296 lockf 268 log 199 logi0 199 lor operator 198 lowercase 216 253 lseek 263 1sl operator 198 lsr operator 198 lstat 264 1t_num 283 lxor operator 198 magenta 303 major 229 make 212 251 Make functor 232 240 248 make_formatter 225 make_image 306 make_lexer 230 make_matrix 213 map 214 236 Map module 239 map2 236 mapi 214 319 Marshal module 240 match_beginning 289 match_end 289 Match_failure exception 89 91 194 matched_group 289 matched_string 289 max 196 max_array_length 254 max_int 198 max_num 283 max_string_length 254 mem 231 237 mem_assoc 238 mem_assq 238 memq 237 merge 248 min 196 min_int 198 min_num 283 minor 229 minus_num 282 mkdir 265 mkfifo 266 mktime 269 mod operator 198 mod_float 200 mod_num 282 modf 200 mouse_pos 307 moveto 304 mult_num
279. on constr decl or label decl The implementation of the type name in a matching structure must be compatible with the type expression specified in the equation if given and have the specified representation if given Conversely users of that signature will be able to rely on the type equation or type representation if given More precisely we have the following four situations Abstract type no equation no representation Names that are defined as abstract types in a signature can be implemented in a matching structure by any kind of type definition provided it has the same number of type param eters The exact implementation of the type will be hidden to the users of the structure In particular if the type is implemented as a variant type or record type the associated constructors and labels will not be accessible to the users if the type is implemented as an abbreviation the type equality between the type name and the right hand side of the abbre viation will be hidden from the users of the structure Users of the structure consider that type as incompatible with any other type a fresh type has been generated Type abbreviation an equation typexp no representation The type name must be implemented by a type compatible with typexp All users of the structure know that the type name is compatible with typexp New variant type or record type no equation a representation The type name must be implemented by a var
280. on list method private trace Euro c operation gt unit method withdraw Euro c gt Euro c end One may wish to open an account and simultaneously deposit some initial amount Although the initial implementation did not address this requirement it can be achieved by using an initializer class account_with_deposit x object inherit account_with_history initializer balance lt x end class account_with_deposit Euro c gt object val mutable balance Euro c val mutable history Euro c operation list method balance Euro c method deposit Euro c gt unit 60 method history Euro c operation list method private trace Euro c operation gt unit method withdraw Euro c gt Euro c end A better alternative is class account_with_deposit x object self inherit account_with_history initializer self deposit x end class account_with_deposit Euro c gt object val mutable balance Euro c val mutable history Euro c operation list method balance Euro c method deposit Euro c gt unit method history Euro c operation list method private trace Euro c operation gt unit method withdraw Euro c gt Euro c end Indeed the latter is safer since the call to deposit will automatically benefit from safety checks and from the trace Let s test it let ccp new account_with_deposit euro 100 in let balance ccp withdraw euro 50 in ccp history
281. on to the C linker when linking in custom runtime mode See the corresponding option for ocamlc in chapter 7 ccopt option Pass the given option to the C compiler and linker when linking in custom runtime mode See the corresponding option for ocamlc in chapter 7 custom Link in custom runtime mode See the corresponding option for ocamlc in chapter 7 I directory Add the given directory to the list of directories searched for compiled object code files cmo and cma o exec file Specify the name of the toplevel file produced by the linker The default is a out Chapter 9 The runtime system ocamlrun The ocamlrun command executes bytecode files produced by the linking phase of the ocamlc command 9 1 Overview The ocamlrun command comprises three main parts the bytecode interpreter that actually ex ecutes bytecode files the memory allocator and garbage collector and a set of C functions that implement primitive operations such as input output The usage for ocamlrun is ocamlrun options bytecode executable arg argn The first non option argument is taken to be the name of the file containing the executable bytecode That file is searched in the executable path as well as in the current directory The remaining arguments are passed to the Caml Light program in the string array Sys argv Element 0 of this array is the name of the bytecode executable file elements 1 to n are the remaining
282. open_hbox formatter gt unit gt unit pp_open_vbox formatter gt int gt unit pp_open_hvbox formatter gt int gt unit pp_open_hovbox formatter gt int gt unit pp_open_box formatter gt int gt unit pp_close_box formatter gt unit gt unit pp_print_string formatter gt string gt unit pp_print_as formatter gt int gt string gt unit pp_print_int formatter gt int gt unit pp_print_float formatter gt float gt unit pp_print_char formatter gt char gt unit pp_print_bool formatter gt bool gt unit pp_print_break formatter gt int gt int gt unit pp_print_cut formatter gt unit gt unit pp_print_space formatter gt unit gt unit pp_force_newline formatter gt unit gt unit pp_print_flush formatter gt unit gt unit pp_print_newline formatter gt unit gt unit pp_print_if_newline formatter gt unit gt unit pp_open_tbox formatter gt unit gt unit pp_close_tbox formatter gt unit gt unit pp_print_tbreak formatter gt int gt int gt unit pp_set_tab formatter gt unit gt unit pp_print_tab formatter gt unit gt unit pp_set_margin formatter gt int gt unit pp_get_margin formatter gt unit gt int pp_set_max_indent formatter gt int gt unit pp_get_max_indent formatter gt unit gt int pp_set_max_boxes formatter
283. or when it tries to read a compiled interface file cmi file that has the wrong structure This means something went wrong when this cmi file was written the disk was full the compiler was interrupted in the middle of the file creation and so on This error can also appear if a cmi file is modified after its creation by the compiler Fix remove the corrupted cmi file and rebuild it This expression has type t but is used with type tz This is by far the most common type error in programs Type t is the type inferred for the expression the part of the program that is displayed in the error message by looking at the expression itself Type tz is the type expected by the context of the expression it is deduced by looking at how the value of this expression is used in the rest of the program If the two types t and t2 are not compatible then the error above is produced In some cases it is hard to understand why the two types t and t are incompatible For instance the compiler can report that expression of type foo cannot be used with type foo and it really seems that the two types foo are compatible This is not always true Two type constructors can have the same name but actually represent different types This can happen if a type constructor is redefined Example type foo A B let f function A gt 0 B gt 1 type foo C D f C This result in the error message expression C of type foo cannot be used with
284. ore_adds expression gt Genlex token Stream t gt expression lt fun gt val parse_mult Genlex token Stream t gt expression lt fun gt val parse_more_mults expression gt Genlex token Stream t gt expression lt fun gt val parse_simple Genlex token Stream t gt expression lt fun gt HH HH HH FH HOH OH OF OF Composing the lexer and parser we finally obtain a function to read an expression from a character string let read_expr s parse_expr lexer Stream of_string s val read_expr string gt expression lt fun gt read_expr 2 xty expression Prod Const 2 Sum Var x Var y 1 9 Standalone Caml programs All examples given so far were executed under the interactive system Caml code can also be compiled separately and executed non interactively using the batch compilers ocamlc or ocamlopt The source code must be put in a file with extension m1 It consists of a sequence of phrases which will be evaluated at runtime in their order of appearance in the source file Unlike in interactive mode types and values are not printed automatically the program must call printing functions explicitly to produce some output Here is a sample standalone program to print Fibonacci numbers File fib ml let rec fib n if n lt 2 then 1 else fib n 1 fib n 2 let main let arg int_of_string Sys argv 1 in print_int fib arg print_newline exit 0 main Chapt
285. patible with type lt notify d gt event gt unit gt as e richer_window_subject as d lt add_observer lt notify Cf richer_window_subject as g gt event gt unit gt as f gt unit draw unit identity int move int gt unit notify_observers event gt unit raise unit resize int gt unit gt window move 1 window resize 2 unit QO Part II The Objective Caml language Chapter 5 The Objective Caml language Foreword This document is intended as a reference manual for the Objective Caml language It lists the language constructs and gives their precise syntax and informal semantics It is by no means a tutorial introduction to the language there is not a single example A good working knowledge of Caml is assumed No attempt has been made at mathematical rigor words are employed with their intuitive meaning without further definition As a consequence the typing rules have been left out by lack of the mathematical framework required to express them while they are definitely part of a full formal definition of the language Notations The syntax of the language is given in BNF like notation Terminal symbols are set in typewriter font like this Non terminal symbols are set in italic font like that Square brackets denote optional components Curly brackets denotes zero one or several repetitions of the enclosed components Curly bracket with
286. pattern If the matching against pattern is successful the name name is bound to the matched value in addition to the bindings performed by the matching against pattern Parenthesized patterns The pattern pattern matches the same values as pattern A type constraint can appear in a parenthesized pattern as in pattern typexpr This constraint forces the type of pattern to be compatible with type Or patterns The pattern pattern pattern represents the logical or of the two patterns pattern and patterns A value matches pattern patterns either if it matches pattern or if it matches patterns The two sub patterns pattern and pattern must contain no identifiers Hence no bindings are returned by matching against an or pattern Variant patterns The pattern ncconstr pattern matches all variants whose constructor is equal to ncconstr and whose argument matches pattern The pattern pattern pattern matches non empty lists whose heads match pattern and whose tails match patterns This pattern behaves like pattern patterns The pattern pattern pattern matches lists of length n whose elements match pattern pattern respectively This pattern behaves like pattern pattern 1 Tuple patterns The pattern pattern pattern matches n tuples whose components match the patterns pattern through pattern That is the pattern matches the tuple values
287. ped as well and can be nested Example a lexer suitable for a desk calculator is obtained by let lexer make_lexer 7 wou gt Wy Tet won i The associated parser would be a function from token stream to for instance int and would have rules such as let parse_expr parser lt Int n gt gt n lt Kwd n parse_expr Kwd gt gt n lt n1 parse_expr n2 parse_remainder n1 gt gt n2 and parse_remainder n1 parser lt Kwd n2 parse_expr gt gt ni n2 17 11 Module Hashtbl hash tables and hash functions Hash tables are hashed association tables with in place modification Chapter 17 The standard library 231 Generic interface type a b t val val val val val val val val The type of hash tables from type a to type b create int gt a b t Hashtbl create n creates a new empty hash table with initial size n The table grows as needed so n is just an initial guess Better results are said to be achieved when n is a prime number clear a b t gt unit Empty a hash table add a b t gt a gt b gt unit Hashtbl add tbl x y adds a binding of x to y in table tbl Previous bindings for x are not removed but simply hidden That is after performing Hashtbl remove tbl x the previous binding for x if any is restored Same behavior as with association lists find Ca b
288. plevel they are listed below in section 8 2 Unix The toplevel system is started by the command ocam1 as follows ocaml options interactive mode ocaml options scriptfile script mode If no filename is given on the command line the toplevel system enters interactive mode phrases are read on standard input results are printed on standard output errors on stan dard error End of file on standard input terminates ocaml see also the quit directive in section 8 2 On start up before the first phrase is read if the file ocamlinit exists in the current directory its contents are read as a sequence of Objective Caml phrases and executed as per the use directive described in section 8 2 The evaluation outcode for each phrase are not displayed The toplevel system does not perform line editing but it can easily be used in conjunction with an external line editor such as fep just run fep emacs ocaml or fep vi ocaml Another option is to use ocaml under Gnu Emacs which gives the full editing power of Emacs see the subdirectory emacs of the Objective Caml distribution At any point the parsing compilation or evaluation of the current phrase can be interrupted by pressing ctrl C or more precisely by sending the sigintr signal to the ocam1 process The toplevel then immediately returns to the prompt If a filename is given on the command line to ocam1 the toplevel system enters script mode the contents of the file are r
289. ports tuple of up to 27 1 elements 4194303 elements 5 2 3 Records Record values are labeled tuples of values The record value written label v1 label Un associates the value v to the record label label for i 1 n The current implementation supports records with up to 2 1 fields 4194308 fields 5 2 4 Arrays Arrays are finite variable sized sequences of values of the same type The current implementation supports arrays containing to 27 1 elements 4194303 elements 5 2 5 Variant values Variant values are either a constant constructor or a pair of a non constant constructor and a value The former case is written cconstr the latter case is written ncconstr v where v is said to be the argument of the non constant constructor ncconstr The following constants are treated like built in constant constructors 80 Constant Constructor false the boolean false true the boolean true O the unit value the empty list The current implementation limits the number of distinct constructors in a given variant type to at most 249 5 2 6 Functions Functional values are mappings from values to values 5 2 7 Objects Objects are composed of a hidden internal state which is a record of instance variables and a set of methods for accessing and modifying these variables The structure of an object is described by the toplevel class that created it 5 3 Names Identifiers
290. pplication The expression module expr module expry evaluates module expr to a functor and module expr to a module and applies the former to the latter The type of module expry must match the type expected for the arguments of the functor module expry 5 12 Compilation units unit interface specification unit implementation definition Compilation units bridge the module system and the separate compilation system A compila tion unit is composed of two parts an interface and an implementation The interface contains a sequence of specifications just as the inside of a sig end signature expression The implemen tation contains a sequence of definitions just as the inside of a struct end module expression A compilation unit also has a name unit name derived from the names of the files containing the interface and the implementation see chapter 7 for more details A compilation unit behaves roughly as the module definition module unit name sig unit interface end struct unit implementation end A compilation unit can refer to other compilation units by their names as if they were regular modules For instance if U is a compilation unit that defines a type t other compilation units can refer to that type under the name U t they can also refer to U as a whole structure Except for names of other compilation units a unit interface or unit implementation must not have any other free variables In othe
291. put val read_line unit gt string Flush standard output then read characters from standard input until a newline character is encountered Return the string of all characters read without the newline character at the end val read_int unit gt int Flush standard output then read one line from standard input and convert it to an integer Raise Failure int_of_string if the line read is not a valid representation of an integer val read_float unit gt float Flush standard output then read one line from standard input and convert it to a floating point number The result is unspecified if the line read is not a valid representation of a floating point number 204 General output functions type open_flag val val val val val Open_rdonly Open_wronly Open_append Open_creat Open_trunc Open_excl Open_binary Open_text Open_nonblock Opening modes for open_out_gen and open_in_gen Open_rdonly open for reading Open_wronly open for writing Open_append open for appending Open_creat create the file if it does not exist Open_trunc empty the file if it already exists Open_excl fail if the file already exists Open_binary open in binary mode no conversion Open_text open in text mode may perform conversions Open_nonblock open in non blocking mode open_out string gt out_channel Open the named file for writing and return a new output channel on that file positionned at t
292. r are function definitions fun or function and the patterns pattern pattern are just value names as in let rec name fun and and name fun in expr This defines name name as mutually recursive functions local to expr The behavior of other forms of let rec definitions is implementation dependent The current implementation also supports a certain class of recursive definitions of non functional values such as let rec name 1 name and names 2 name in expr which binds name to the cyclic list 1 2 1 2 and name to the cyclic list 2 1 2 1 Informally the class of accepted definitions consists of those definitions where the defined names occur only inside function bodies or as argument to a data constructor Chapter 5 The Objective Caml language 91 5 7 2 Control structures Sequence The expression expr expr evaluates expr first then expr and returns the value of expr Conditional The expression if expr then expr else expr evaluates to the value of expr if expr evaluates to the boolean true and to the value of expr if expr evaluates to the boolean false The else expr part can be omitted in which case it defaults to else Case expression The expression match expr with pattern gt expr l pattern gt expr matches the value of expr against the patterns pattern to pattern If the matching against pattern succeeds the associated expression
293. r c method center center method set_center c center lt c method move center move end class a circle 2a gt object constraint a point val mutable center a method center a method move int gt unit method set_center a gt unit end The class colored_circle is a specialized version of class circle which requires the type of the center to unify with colored_point and adds a method color Note that when specializing a parameterized class the instance of type parameter must always be explicitly given It is again written inside and Chapter 2 Objects in Caml 37 class a colored_circle c object constraint a colored_point inherit a circle c method color center color end class a colored_circle 2a gt object constraint a colored_point val mutable center a method center a method color string method move int gt unit method set_center a gt unit end 2 10 Using coercions Subtyping is never implicit There are however two ways to perform subtyping The most general construction is fully explicit both the domain and the codomain of the type coercion must be given We have seen that points and colored points have incompatible types For instance they cannot be mixed in the same list However a colored point can be coerced to a point hiding its color method let colored_point_to_point cp cp
294. r the most frequently used commands ambiguous abbreviations are allowed For instance r stands for run even though there are others commands starting with r You can test the validity of an abbreviation using the help command If the previous command has been successful a blank line typing just RET will repeat it 13 3 1 Getting help The Objective Caml debugger has a simple on line help system which gives a brief description of each command and variable help Print the list of commands help command Give help about the command command Chapter 13 The debugger ocamldebug 155 help set variable help show variable Give help about the variable variable The list of all debugger variables can be obtained with help set help info topic Give help about topic Use help info to get a list of known topics 13 3 2 Accessing the debugger state set variable value Set the debugger variable variable to the value value show variable Print the value of the debugger variable variable info subject Give information about the given subject For instance info breakpoints will print the list of all breakpoints 13 4 Executing a program 13 4 1 Events Events are interesting locations in the source code corresponding to the beginning or end of evaluation of interesting sub expressions Events are the unit of single stepping stepping goes to the next or previous event encountered in the program execution Also breakp
295. r 17 The standard library 249 val create unit gt at Return a new stack initially empty val push a gt a t gt unit push x s adds the element x at the top of stack s val pop at gt a pop s removes and returns the topmost element in stack s or raises Empty if the stack is empty val clear a t gt unit Discard all elements from a stack val length a t gt int Return the number of elements in a stack val iter a gt unit gt a t gt unit iter f s applies f in turn to all elements of s from the element at the top of the stack to the element at the bottom of the stack The stack itself is unchanged 17 26 Module Stream streams and parsers type at The type of streams holding values of type a exception Failure Raised by parsers when none of the first components of the stream patterns is accepted exception Error of string Raised by parsers when the first component of a stream pattern is accepted but one of the following components is rejected 250 Stream builders Warning these functions create streams with fast access it is illegal to mix them with streams built with lt gt would raise Failure when accessing such mixed streams val from int gt a option gt a t Stream from f returns a stream built from the function f To create a new stream element the function f is called with the current stream count The user function f must return
296. r a parsing function has returned to remove all pointers from the parser stack to structures that were built by semantic actions during parsing This is optional but lowers the memory requirements of the programs exception Parse_error Raised when a parser encounters a syntax error Can also be raised from the action part of a grammar rule to initiate error recovery 17 19 Module Printexc a catch all exception handler val catch a gt b gt a gt b Printexc catch fn x applies fn to x and returns the result If the evaluation of fn x raises any exception the name of the exception is printed on standard error output and the programs aborts with exit code 2 Typical use is Printexc catch main where main with type unit gt unit is the entry point of a standalone program This catches and reports any exception that escapes the program val print a gt b gt a gt b Same as catch but re raise the stray exception after printing it instead of aborting the program val to_string exn gt string Printexc to_string e returns a string representation of e 17 20 Module Printf formatting printing functions val fprintf out_channel gt a out_channel unit format gt a fprintf outchan format argi argN formats the arguments arg1 to argN according to the format string format and outputs the resulting string on the channel outchan The format is a character string which contains
297. r process signals in Windows not implemented not implemented always return 1 not implemented not implemented always raise Not_found always raise Not_found the domain PF_UNIX is not supported PF_INET is fully supported not implemented use threads not implemented 279 280 Chapter 19 The num library arbitrary precision rational arithmetic The num library implements exact precision rational arithmetic It is built upon the state of the art BigNum arbitrary precision integer arithmetic package and therefore achieves very high performance The functions provided in this library are fully documented in The CAML Numbers Reference Manual by Val rie M nissier Morain technical report 141 INRIA july 1992 available electron ically ftp ftp inria fr INRIA publication RT RT 0141 ps gz A summary of the func tions is given below Programs that use the num library must be linked in custom runtime mode as follows ocamlc custom other options nums cma other files cclib lnums ocamlopt other options nums cmxa other files cclib 1lnums For interactive use of the nums library do ocamlmktop custom o mytop nums cma cclib lnums mytop 19 1 Module Num operation on arbitrary precision numbers open Nat open Big_int open Ratio Numbers type num are arbitrary precision rational numbers plus the special elements 1 0 infinity and 0 0 undefined type num Int of int Big_int of big_int R
298. r terms the type checking and compilation of an interface or implementation proceeds in the initial environment name sig interface end name sig interface end where name namey are the names of the other compilation units available in the search path see chapter 7 for more details and interface interface are their respective interfaces 110 Chapter 6 Language extensions This chapter describes the language features that are implemented in Objective Caml but not described in the Objective Caml reference manual In contrast with the fairly stable kernel language that is described in the reference manual the extensions presented here are still experimental and may be removed or changed in the future 6 1 Streams and stream parsers Objective Caml comprises a library type for streams possibly infinite sequences of elements that are evaluated on demand and associated stream expressions to build streams and stream patterns to destructure streams Streams and stream patterns provide a natural approach to the writing of recursive descent parsers Streams are presented by the following extensions to the syntactic classes of expressions expr stream component stream matching stream pattern stream pat comp lt gt lt stream component stream component gt parser pattern stream matching match expr with parser pattern stream matching gt expr expr stream pattern pattern gt
299. re a is the parameter of the stack The parameter b is not related to the class a stack but to the argument that will be passed to the method fold The intuition is that method fold should be polymorphic i e of type All Ca Cb gt a gt b gt b gt b which is not currently possible One possibility would be to make b an extra parameter of class stack class a b stack2 object inherit a stack method fold f x b List fold_left f x 1 end class a b stack2 object val mutable 1 a list method clear unit method fold b gt a gt b gt b gt b method length int method pop a method push a gt unit end However the method fold of a given object can only be applied to functions that all have the same type let s new stack2 val s _a _b stack2 lt obj gt s fold 0 int 0 s int int stack2 lt obj gt The best solution would be to make method fold polymorphic However OCaml does not currently allow methods to be polymorphic Thus the current solution is to leave the function fold outside of the class class a stack3 object inherit a stack method iter f List iter f a gt unit 1 Chapter 4 Advanced examples with classes and modules 67 end class a stack3 object val mutable 1 a list method clear unit method iter
300. reading as above The extra arguments mode and rights specify the opening mode and file permissions open_in and open_in_bin are special cases of this function input_char in_channel gt char Read one character from the given input channel Raise End_of_file if there are no more characters to read input_line in_channel gt string Read characters from the given input channel until a newline character is encountered Return the string of all characters read without the newline character at the end Raise End_of_file if the end of the file is reached at the beginning of line input in_channel gt string gt int gt int gt int input chan buff ofs len attempts to read len characters from channel chan storing them in string buff starting at character number ofs It returns the actual number of characters read between 0 and len inclusive A return value of 0 means that the end of file was reached A return value between 0 and len exclusive means that no more characters were available at that time input must be called again to read the remaining characters if desired Exception Invalid_argument input is raised if ofs and len do not designate a valid substring of buff really_input in_channel gt string gt int gt int gt unit really_input chan buff ofs len reads len characters from channel chan storing them in string buff starting at character number ofs Raise End_of_file if the end of file is reached
301. ready locked Commands for lockf val lockf file_descr gt lock_command gt int gt unit lockf fd cmd size puts a lock on a region of the file opened as fd The region starts at the current read write position for fd as set by 1seek and extends size bytes forward if size is positive size bytes backwards if size is negative or to the end of the file if size is zero A write lock set with F_LOCK or F_TLOCK prevents any other process from acquiring a read or write lock on the region A read lock set with F_RLOCK or F_TRLOCK prevents any other process from acquiring a write lock on the region but lets other processes acquire read locks on it Signals val kill int gt int gt unit kill pid sig sends signal number sig to the process with id pid type sigprocmask_command SIG_SETMASK SIG_BLOCK SIG_UNBLOCK val sigprocmask sigprocmask_command gt int list gt int list sigprocmask cmd sigs changes the set of blocked signals If cmd is SIG_SETMASK blocked signals are set to those in the list sigs If cmd is SIG_BLOCK the signals in sigs are added to the set of blocked signals If cmd is SIG_UNBLOCK the signals in sigs are removed from the set of blocked signals sigprocmask returns the set of previously blocked signals val sigpending unit gt int list Return the set of blocked signals that are currently pending val sigsuspend int list gt unit sigsuspend sigs atomically sets the blocked signals to sig and
302. red in C the following functions actually raise the exception e raise_constant id raises the exception id with no argument e raise_with_arg id v raises the exception id with the Caml value v as argument e raise_with_string id s where s is a null terminated C string raises the exception id with a copy of the C string s as argument 15 5 Living in harmony with the garbage collector Unused blocks in the heap are automatically reclaimed by the garbage collector This requires some cooperation from C code that manipulates heap allocated blocks 15 5 1 Simple interface All the macros described in this section are declared in the memory h header file Rule 1 A function that has parameters or local variables of type value must begin with a call to one of the CAMLparam macros and return with CAMLreturn There are six CAMLparam macros CAMLparamO to CAMLparam5 which take zero to five arguments respectively If your function has fewer than 5 parameters of type value use the corresponding macros with these parameters as arguments If your function has more than 5 parameters of type value use CAMLparam5 with five of these parameters and use one or more calls to the CAMLxparam macros for the remaining parameters CAMLxparamO to CAMLxparam5 The macro CAMLreturn is used as a direct replacement for the C keyword return All occurences of return must be replaced by CAMLreturn including the implicit return at the end of a procedure void
303. resources are consumed by the finalized block being allocated you give the amount of resources allocated to this object as parameter used and the maximum amount that you want to see in floating garbage as parameter maz The units are arbitrary the GC cares only about the ratio used maz For instance if you are allocating a finalized block holding an X Windows bitmap of w by h pixels and you d rather not have more than 1 mega pixels of unreclaimed bitmaps specify used w x h and max 1000000 If your finalized blocks contain no pointers to out of heap resources or if the previous discussion made little sense to you just take used 0 and maz 1 But if you later find that the finalization functions are not called often enough consider increasing the used maz ratio 15 4 6 Raising exceptions Two functions are provided to raise two standard exceptions e failwith s where s is a null terminated C string with type char raises exception Failure with argument s e invalid_argument s where s is a null terminated C string with type char raises ex ception Invalid_argument with argument s Raising arbitrary exceptions from C is more delicate the exception identifier is dynamically allocated by the Caml program and therefore must be communicated to the C function using the Chapter 15 Interfacing C with Objective Caml 179 registration facility described below in section 15 6 3 Once the exception identifier is recove
304. ression class path evaluates to the class bound to the name class path Similarly the ex pression typexpr typexpr class path evaluates to the parametric class bound to the name class path in which type parameters have been instanciated to respectively typexpr typexpr The expression class expr evaluates to the same module as class expr The expression class expr class type checks that class type match the type of class expr that is that the implementation class expr meets the type specification class type The whole expression evaluates to the same class as class expr except that all components not specified in class type are hidden and can no longer be accessed Class application Class application is denoted by juxtaposition of expressions The expression class expr expr eval uates the expressions class expr and expr The expression class expr must evaluate to a functional class value which is then applied to the value of expr 100 Class function The expression fun pattern gt class expr evaluates to a function from values to classes When this function is applied to a value v this value is matched against the pattern pattern and the result is the result of the evaluation of class expr in the extended environment The expression fun pattern pattern gt class expr is a short form for fun pattern gt fun pattern gt expr Local definitions The let and let rec constructs bind va
305. returning function Example void foo value vi value v2 value v3 CAMLparam3 v1 v2 v3 CAMLreturn Note if your function is a primitive with more than 5 arguments for use with the byte code runtime its arguments are not values and must not be declared they have types value and int Rule 2 Local variables of type value must be declared with one of the CAMLlocal macros Arrays of values are declared with CAMLlocalN 180 The macros CAMLlocali to CAMLlocal5 declare and initialize one to five local variables of type value The variable names are given as arguments to the macros CAMLlocalN z n declares and initializes a local variable of type value n You can use several calls to these macros if you have more than 5 local variables You can also use them in nested C blocks within the function Example value bar value vi value v2 value v3 CAMLparam3 v1 v2 v3 CAMLlocall result result alloc 3 0 CAMLreturn result Rule 3 Assignments to the fields of structured blocks must be done with the Store_field macro Store_field b n v stores the value v in the field number n of value b which must be a block i e Is_block b must be true Example value bar value vi value v2 value v3 CAMLparam3 v1 v2 v3 CAMLlocali result result alloc 3 0 Store_field result 0 v1 Store_field result 1 v2 Store_field result 2 v3 CAMLreturn result Rule 4 Globa
306. rint_string f is applied to print_int n print_newline let _ Callback register test function f On the C side a pointer to the value registered under name n is obtained by calling caml_named_value n The returned pointer must then be dereferenced to recover the actual Caml value If no value is registered under the name n the null pointer is returned For example here is a C wrapper that calls the Caml function f above void call_caml_f int arg callback caml_named_value test function Val_int arg 184 The pointer returned by caml_named_value is constant and can safely be cached in a C variable to avoid repeated name lookups On the other hand the value pointed to can change during garbage collection and must always be recomputed at the point of use Here is a more efficient variant of call_caml_f above that calls caml_named_value only once void call_caml_f int arg static value closure_f NULL if closure_f NULL First time around look up by name closure_f caml_named_value test function callback closure_f Val_int arg 15 6 3 Registering Caml exceptions for use in C functions The registration mechanism described above can also be used to communicate excep tion identifiers from Caml to C The Caml code registers the exception by evaluating Callback register_exception n ezn where n is an arbitrary name and ezn is an exception value of the exception to register For example
307. rite except that Unix_error ETIMEDOUT _ _ is raised if no data is available for reading or ready for writing after d seconds The delay d is given in the fifth argument in seconds Polling val select Unix file_descr list gt Unix file_descr list gt Unix file_descr list gt float gt Unix file_descr list Unix file_descr list Unix file_descr list Pipes and redirections val pipe unit gt Unix file_descr Unix file_descr val open_process_out string gt out_channel val open_process string gt in_channel out_channel Time val sleep int gt unit Sockets val socket Unix socket_domain gt Unix socket_type gt int gt Unix file_descr val socketpair Unix socket_domain gt Unix socket_type gt int gt Unix file_descr Unix file_descr val accept Unix file_descr gt Unix file_descr Unix sockaddr val connect Unix file_descr gt Unix sockaddr gt unit 300 val val val val val val recv Unix file_descr gt string gt int gt int gt Unix msg_flag list gt int recvfrom Unix file_descr gt string gt int gt int gt Unix msg_flag list gt int Unix sockaddr send Unix file_descr gt string gt int gt int gt Unix msg_flag list gt int sendto Unix file_descr gt string gt int gt int gt Unix msg_flag list gt Unix sockaddr gt int open_connection Unix sockaddr gt in_channel out_channel establish_server in_chann
308. rn a string describing the given error code val handle_unix_error a gt b gt a gt b handle_unix_error f x applies f to x and returns the result If the exception Unix_error is raised it prints a message describing the error and exits with code 2 Access to the process environment val environment unit gt string array Return the process environment as an array of strings with the format variable value val getenv string gt string Return the value associated to a variable in the process environment Raise Not_found if the variable is unbound This function is identical to Sys getenv 260 val putenv string gt string gt unit Unix putenv name value sets the value associated to a variable in the process environment name is the name of the environment variable and value its new associated value Process handling type process_status WEXITED of int WSIGNALED of int WSTOPPED of int The termination status of a process WEXITED means that the process terminated normally by exit the argument is the return code WSIGNALED means that the process was killed by a signal the argument is the signal number WSTOPPED means that the process was stopped by a signal the argument is the signal number type wait_flag WNOHANG WUNTRACED Flags for waitopt and waitpid WNOHANG means do not block if no child has died yet but immediately return with a pid equal to 0 WUNTRACED means report al
309. room on the line to print the remainder of the box When a new line is printed in the box d is added to the current indentation Tabulations val open_tbox unit gt unit Open a tabulation box val close_tbox unit gt unit Close the most recently opened tabulation box val print_tbreak int gt int gt unit Break hint in a tabulation box print_tbreak spaces offset moves the insertion point to the next tabulation spaces being added to this position Nothing occurs if insertion point is already on a tabulation mark If there is no next tabulation on the line then a newline is printed and the insertion point moves to the first tabulation of the box If a new line is printed offset is added to the current indentation val set_tab unit gt unit Set a tabulation mark at the current insertion point val print_tab unit gt unit print_tab is equivalent to print_tbreak 0 0 Chapter 17 The standard library Ellipsis val set_ellipsis_text string gt unit Set the text of the ellipsis printed when too many boxes are opened a single dot by default val get_ellipsis_text unit gt string Return the text of the ellipsis Redirecting formatter output val set_formatter_out_channel out_channel gt unit Redirect the pretty printer output to the given channel val set_formatter_output_functions string gt int gt int gt unit gt unit gt unit gt unit 223
310. rray gt file_descr gt file_descr gt file_descr gt int create_process_env prog args env new_stdin new_stdout new_stderr works as create_process except that the extra argument env specifies the environment passed to the program Chapter 18 The unix library Unix system calls 267 val val val val val val val val open_process_in string gt in_channel open_process_out string gt out_channel open_process string gt in_channel out_channel High level pipe and process management These functions run the given command in parallel with the program and return channels connected to the standard input and or the standard output of the command The command is interpreted by the shell bin sh cf system Warning writes on channels are buffered hence be careful to call flush at the right times to ensure correct synchronization open_process_full string gt string array gt in_channel out_channel in_channel Similar to open_process but the second argument specifies the environment passed to the command The result is a triple of channels connected to the standard output standard input and standard error of the command close_process_in in_channel gt process_status close_process_out out_channel gt process_status close_process in_channel out_channel gt process_status close_process_full in_channel out_channel in_channel gt process_status Close channels opened by open_process_in op
311. rray fold_right f a x computes f a 0 f a 1 a n 1 x where n is the length of the array a 17 3 Module Buffer extensible string buffers This module implements string buffers that automatically expand as necessary It provides accumulative concatenation of strings in quasi linear time instead of quadratic time when strings are concatenated pairwise type t val The abstract type of buffers create int gt t create n returns a fresh buffer initially empty The n parameter is the initial size of the internal string that holds the buffer contents That string is automatically reallocated when more than n characters are stored in the buffer but shrinks back to n characters when reset is called For best performance n should be of the same order of magnitude as the number of characters that are expected to be stored in the buffer for instance 80 for a buffer that holds one output line Nothing bad will happen if the buffer grows beyond that limit however In doubt take n 16 for instance If n is not between 1 and Sys max_string_length it will be clipped to that interval Chapter 17 The standard library 215 val val val val val val val val val val contents t gt string Return a copy of the current contents of the buffer The buffer itself is unchanged length t gt int Return the number of characters currently contained in the buffer clear t gt unit Empty t
312. rs event gt unit end class subject window_observer object inherit subject event observer method notify s e s draw end class a window_observer object constraint a lt draw unit gt method notify a gt event gt unit end Unsurprisingly the type of window is recursive let window new window_subject val window lt notify a gt event gt unit _ gt window_subject as a lt obj gt However the two classes of window_subject and window_observer are not mutually recursive let window_observer new window_observer val window_observer lt draw unit _ gt window_observer lt obj gt window add_observer window_observer Characters 20 35 This expression has type lt draw unit gt as a window_observer lt notify a gt event gt unit gt but is here used with type lt notify b window_subject as c gt event gt unit gt as b Chapter 4 Advanced examples with classes and modules 71 Type a is not compatible with type lt notify d gt event gt unit gt as e window_subject as d lt add_observer lt notify Cf window_subject as g gt event gt unit gt as f gt unit draw unit identity int move int gt unit notify_observers event gt unit gt window move 1 unit Classes window_observer and window_subject can still
313. rs for arbitrary key types include Hashtbl hash for comparing objects by structure and Hashtbl hash for comparing objects by addresses e g for mutable or cyclic keys module type S sig type key type at val create int gt at val clear a t gt unit val add a t gt key gt a gt unit val remove a t gt key gt unit val find a t gt key gt a val find_all a t gt key gt a list val mem a t gt key gt bool val iter key gt a gt unit gt a t gt unit end module Make H HashedType S with type key H t The functor Hashtbl Make returns a structure containing a type key of keys and a type a t of hash tables associating data of type a to keys of type key The operations perform similarly to those of the generic interface but use the hashing and equality functions specified in the functor argument H instead of generic equality and hashing The polymorphic hash primitive val hash a gt int Hashtbl hash x associates a positive integer to any value of any type It is guaranteed that ifx y then hash x hash y Moreover hash always terminates even on cyclic structures Chapter 17 The standard library 233 val hash_param int gt int gt a gt int Hashtbl hash_param n m x computes a hash value for x with the same properties as for hash The two extra parameters n and m give more precise control o
314. rs s n returns the first n characters of s This is the same function as string_before val last_chars string gt int gt string last_chars s n returns the last n characters of s 291 292 Chapter 21 The threads library The threads library allows concurrent programming in Objective Caml It provides multiple threads of control also called lightweight processes that execute concurrently in the same memory space Threads communicate by in place modification of shared data structures or by sending and receiving data on communication channels The threads library is implemented by time sharing on a single processor It will not take advantage of multi processor machines Using this library will therefore never make programs run faster However many programs are easier to write when structured as several communicating processes Unix Programs that use the threads library must be linked as follows ocamlc thread custom other options threads cma other files cclib lthreads The thread option selects a special thread safe version of the standard library see chap ter 7 The thread option must also be given when compiling any source file that references modules from the thread library Thread Mutex The default thread implementation cannot be used in native code programs compiled with ocamlopt If your operating system provides POSIX 1003 1c compliant threads you can select an alternate implementation when configur
315. rt over arrays let insertion_sort a for i 1 to Array length a 1 do let val_i a i in let j ref i in while j gt 0 amp amp val_i lt a j 1 do a j lt a j 1 j lj S lt 1 HH H HH H OF Chapter 1 The core language 17 done a j lt val_i done val insertion_sort a array gt unit lt fun gt References are also useful to write functions that maintain a current state between two calls to the function For instance the following pseudo random number generator keeps the last returned number in a reference let current_rand ref 0 val current_rand int ref contents 0 let random current_rand current_rand 25713 1345 current_rand val random unit gt int lt fun gt Again there is nothing magic with references they are implemented as a one field mutable record as follows type a ref mutable contents a type a ref mutable contents a let r r contents val a ref gt a lt fun gt let r newval r contents lt newval val a ref gt a gt unit lt fun gt 1 6 Exceptions Caml provides exceptions for signalling and handling exceptional conditions Exceptions can also be used as a general purpose non local control structure Exceptions are declared with the exception construct and signalled with the raise operator For instance the function below for ta
316. rtual type parameters class name class body type A class type definition class class name class body type defines an abbreviation class name for the class body type class body type As for class definitions two type abbreviations class name and class name are also defined The definition can be parameterized by some type parameters If any method in the class type body is virtual the definition must be flagged virtual Two class type definitions match if they have the same type parameters and the types they expand to match Chapter 5 The Objective Caml language 103 5 10 Module types module specifications Module types are the module level equivalent of type expressions they specify the general shape and type properties of modules module type modtype path sig specification end functor module name module type gt module type module type with mod constraint and mod constraint module type specification val value name typexpr external value name typexpr external declaration type definition exception definition class specification classtype definition module module name module type module module name module name module type module type module type modtype name module type modtype name module type open module path include modtype path mod constraint type type parameters typeconstr typexpr module module path extended module path 5 10 1 Simple mod
317. rules sections and between and as in Caml in the header and trailer sections Chapter 11 Lexer and parser generators ocamllex ocamlyacc 145 11 4 1 Header and trailer The header and the trailer sections are Caml code that is copied as is into file grammar m1 Both sections are optional The header goes at the beginning of the output file it usually contains open directives and auxiliary functions required by the semantic actions of the rules The trailer goes at the end of the output file 11 4 2 Declarations Declarations are given one per line They all start with a sign token symbol symbol Declare the given symbols as tokens terminal symbols These symbols are added as constant constructors for the token concrete type token lt type gt symbol symbol Declare the given symbols as tokens with an attached attribute of the given type These symbols are added as constructors with arguments of the given type for the token concrete type The type part is an arbitrary Caml type expression except that all type constructor names must be fully qualified e g Modname typename for all types except standard built in types even if the proper open directives e g open Modname were given in the header section That s because the header is copied only to the m1 output file but not to the mli output file while the type part of a token declaration is copied to both start symbol symbol Declare the
318. s The unix library makes many Unix system calls and system related library functions available to Objective Caml programs This chapter describes briefly the functions provided Refer to sections 2 and 3 of the Unix manual for more details on the behavior of these functions Not all functions are provided by all Unix variants If some functions are not available they will raise Invalid_arg when called Programs that use the unix library must be linked in custom runtime mode as follows ocamlc custom other options unix cma other files cclib lunix ocamlopt other options unix cmxa other files cclib lunix For interactive use of the unix library do ocamlmktop custom o mytop unix cma cclib lunix mytop Windows A fairly complete emulation of the Unix system calls is provided in the Windows version of Objective Caml The end of this chapter gives more information on the functions that are not supported under Windows 18 1 Module Unix interface to the Unix system Error report type error Errors defined in the POSIX standard E2BIG Argument list too long EACCES Permission denied EAGAIN Resource temporarily unavailable try again EBADF Bad file descriptor EBUSY Resource unavailable ECHILD No child process 257 258 EDEADLK EDOM EEXIST EFAULT EFBIG EINTR EINVAL EIO EISDIR EMF ILE EMLINK ENAMETOOLONG ENFILE ENODEV
319. s do not make sense exception Failure of string Exception raised by library functions to signal that they are undefined on the given arguments exception Not_found Exception raised by search functions when the desired object could not be found exception Out_of_memory Exception raised by the garbage collector when there is insufficient memory to complete the computation exception Stack_overflow Exception raised by the bytecode interpreter when the evaluation stack reaches its maximal size This often indicates infinite or excessively deep recursion in the user s program exception Sys_error of string Exception raised by the input output functions to report an operating system error exception End_of_file Exception raised by input functions to signal that the end of file has been reached exception Division_by_zero Exception raised by division and remainder operations when their second argument is null exception Exit This exception is not raised by any library function It is provided for use in your programs exception Sys_blocked_io A special case of Sys_error raised when no I O is possible on a non blocking I O channel val invalid_arg string gt a Raise exception Invalid_argument with the given string val failwith string gt a Raise exception Failure with the given string 196 Comparisons val val val val val val val val val val val a gt a gt bool e1 e2 te
320. s in expr type This constraint forces the type of expr to be compatible with type Chapter 5 The Objective Caml language 89 Parenthesized expressions can also contain coercions expr type gt type see subsec tion 5 7 5 below Function application Function application is denoted by juxtaposition of expressions The expression expr Xpry expr evaluates the expressions expr to expr The expression expr must evaluate to a functional value which is then applied to the values of expry expr The order in which the expressions expr expr are evaluated is not specified Function definition Two syntactic forms are provided to define functions The first form is introduced by the keyword function function pattern gt expr pattern gt expr This expression evaluates to a functional value with one argument When this function is applied to a value v this value is matched against each pattern pattern to pattern If one of these matchings succeeds that is if the value v matches the pattern pattern for some i then the expression expr associated to the selected pattern is evaluated and its value becomes the value of the function application The evaluation of expr takes place in an environment enriched by the bindings performed during the matching If several patterns match the argument v the one that occurs first in the function definition is selected If none of the patterns matches t
321. s pressed false otherwise val read_key unit gt char Wait for a key to be pressed and return the corresponding character Keypresses are queued val key_pressed unit gt bool Return true if a keypress is available that is if read_key would not block 308 Sound val sound int gt int gt unit sound freq dur plays a sound at frequency freq in hertz for a duration dur in milliseconds Chapter 23 The dbm library access to NDBM databases The dbm library provides access to NDBM databases under Unix NDBM databases maintain key data associations where both the key and the data are arbitrary strings They support fairly large databases several gigabytes and can retrieve a keyed item in one or two file system accesses Refer to the Unix manual pages for more information Unix Programs that use the dbm library must be linked in custom runtime mode as follows ocamlc custom other options dbm cma other files cclib lmldbm cclib 1lndbm ocamlopt other options dbm cmxa other files cclib lmldbm cclib lndbm For interactive use of the dbm library do ocamlmktop custom o mytop dbm cma cclib lmldbm cclib lndbm mytop Depending on the Unix system used the cclib lndbm option is not always necessary or the library may have another name than 1ndbm Windows This library is not available 23 1 Module Dbm interface to the NDBM databases type t The type of file descriptors opened o
322. s to the unit value The expression for name expr to expr do expr done first evaluates the expressions expr and exprs the boundaries into integer values n and p Then the loop body expr is repeatedly evaluated in an environment where name is successively bound to the values n n 1 p 1 p The loop body is never evaluated if n gt p The expression for name expr downto expr do exprz done evaluates similarly except that name is successively bound to the values n n 1 p 1 p The loop body is never evaluated ifn lt p In both cases the whole for expression evaluates to the unit value Exception handling The expression try expr with pattern gt expr pattern gt expr evaluates the expression expr and returns its value if the evaluation of expr does not raise any exception If the evaluation of expr raises an exception the exception value is matched against the patterns pattern to pattern If the matching against pattern succeeds the associated expression expr is evaluated and its value becomes the value of the whole try expression The evaluation of expr takes place in an environment enriched by the bindings performed during matching If several patterns match the value of expr the one that occurs first in the try expression is selected If none of the patterns matches the value of expr the exception value is raised again thereby transparently passing through the try construct 5 7 3
323. se Node rprio relt left remove_top right let extract function Empty gt raise Queue_is_empty Node prio elt _ _ as queue gt prio elt remove_top queue end module PrioQueue sig type priority int and a queue Empty Node of priority a a queue a queue val empty a queue val insert a queue gt priority gt a gt a queue exception Queue_is_empty val remove_top a queue gt a queue val extract a queue gt priority a a queue end Outside the structure its components can be referred to using the dot notation that is identifiers qualified by a structure name For instance PrioQueue insert in a value context is the function insert defined inside the structure PrioQueue Similarly PrioQueue queue in a type context is the type queue defined in PrioQueue PrioQueue insert PrioQueue empty 1 hello string PrioQueue queue PrioQueue Node 1 hello PrioQueue Empty PrioQueue Empty 3 2 Signatures Signatures are interfaces for structures A signature specifies which components of a structure are accessible from the outside and with which type It can be used to hide some components of a structure e g local function definitions or export some components with a restricted type For instance the signature below specifies the three priority queue operations empty insert and extract but not the auxiliary function remove_top Simi
324. select evl is shorthand for sync choose ev1 poll a event gt a option Non blocking version of sync offer all the communication possibilities specified in the event to the outside world and if one can take place immediately perform it and return Some r where r is the result value of that communication Otherwise return None without blocking 21 5 Module ThreadUnix thread compatible system calls This module reimplements some of the functions from Unix so that they only block the calling thread not all threads in the program if they cannot complete immediately See the documentation of the Unix module for more precise descriptions of the functions below Chapter 21 The threads library 299 Process handling val execv string gt string array gt unit val execve string gt string array gt string array gt unit val execvp string gt string array gt unit val wait unit gt int Unix process_status val waitpid Unix wait_flag list gt int gt int Unix process_status val system string gt Unix process_status Basic input output val read Unix file_descr gt string gt int gt int gt int val write Unix file_descr gt string gt int gt int gt int Input output with timeout val timed_read Unix file_descr gt string gt int gt int gt float gt int val timed_write Unix file_descr gt string gt int gt int gt float gt int Behave as read and w
325. sented as float arrays componentwise let add_vect vi v2 let len min Array length vi Array length v2 in let res Array create len 0 0 in for i 0 to len 1 do res i lt vi i v2 i done r s val add_vect float array gt float array gt float array lt fun gt add_vect 1 0 2 0 I 3 0 4 0 float array l4 6l Record fields can also be modified by assignment provided they are declared mutable in the definition of the record type type mutable_point mutable x float mutable y float type mutable_point mutable x float mutable y float let translate p dx dy p x lt p x dx p y lt p y dy val translate mutable_point gt float gt float gt unit lt fun gt let mypoint x 0 0 y 0 0 val mypoint mutable_point x 0 y 0 translate mypoint 1 0 2 0 unit 0 mypoint mutable_point x 1 y 2 Caml has no built in notion of variable identifiers whose current value can be changed by assignment The let binding is not an assignment it introduces a new identifier with a new scope However the standard library provides references which are mutable indirection cells or one element arrays with operators to fetch the current contents of the reference and to assign the contents Variables can then be emulated by let binding a reference For instance here is an in place insertion so
326. set_formatter_output_functions out flush redirects the pretty printer output to the functions out and flush The out function performs the pretty printer output It is called with a string s a start position p and a number of characters n it is supposed to output characters p to ptn 1 of s The flush function is called whenever the pretty printer is flushed using print_flush or print_newline val get_formatter_output_functions unit gt string gt int gt int gt unit unit gt unit Return the current output functions of the pretty printer Changing the meaning of indentation and line breaking val set_all_formatter_output_functions string gt int gt int gt unit gt unit gt unit gt unit gt unit gt int gt unit gt unit set_all_formatter_output_functions out flush outnewline outspace redirects the pretty printer output to the functions out and flush as described in set_formatter_output_functions In addition the pretty printer function that outputs a newline is set to the function outnewline and the function that outputs indentation spaces is set to the function outspace This way you can change the meaning of indentation which can be something else than just printing a space character and the meaning of new lines opening which can be connected to any other action needed by the application at hand The two functions outspace and outnewline are normally connected to out an
327. setsid unit gt int Put the calling process in a new session and detach it from its controlling terminal Windows Below is a list of the functions that are not implemented or only partially implemented under Windows Functions not mentioned are fully implemented and behave as described previously in this chapter Chapter 18 The unix library Unix system calls Functions Comment fork not implemented use create_process or threads wait not implemented use waitpid waitpid can only wait for a given PID not any child process getppid not implemented meaningless under Windows nice not implemented truncate ftruncate lstat fstat link symlink readlink fchmod chown fchown umask set_nonblock clear_nonblock rewinddir mkfifo select lockf kill pause alarm times getitimer setitimer getuid getgid getgid getegid getgroups setuid setgid getpwnam getpwuid getgrnam getgrgid type socket_domain establish_server terminal functions tc not implemented not implemented not implemented no links under Windows not implemented not implemented make no sense on a DOS file system not implemented implemented as dummy functions use threads instead of non blocking I O not implemented re open the directory instead not implemented implemented but works only for sockets use threads if you need to wait on other kinds of file descriptors not implemented not implemented no inte
328. sions and high level string processing Regular expressions type regexp The type of compiled regular expressions val regexp string gt regexp Compile a regular expression The syntax for regular expressions is the same as in Gnu Emacs The special characters are The following constructs are recognized matches any character except newline postfix matches the previous expression zero one or several times postfix matches the previous expression one or several times postfix matches the previous expression once or not at all 287 288 val val val val character set ranges are denoted with as in a z an initial as in 70 9 complements the set T matches at beginning of line matches at end of line I infix alternative between two expressions C grouping and naming of the enclosed expression 1 the text matched by the first expression 2 for the second expression etc b matches word boundaries quotes special characters regexp_case_fold string gt regexp Same as regexp but the compiled expression will match text in a case insensitive way uppercase and lowercase letters will be considered equivalent quote string gt string Str quote s returns a regexp string that matches exactly s and nothing else regexp_string string gt regexp regexp_string_case_fold string gt regexp Str regexp_string s returns a regular expression that matches exactly s and
329. sition SEEK_END relative to the end of the file val lseek file_descr gt int gt seek_command gt int Set the current position for a file descriptor val truncate string gt int gt unit Truncates the named file to the given size val ftruncate file_descr gt int gt unit Truncates the file corresponding to the given descriptor to the given size File statistics type file_kind S_REG Regular file S_DIR Directory S_CHR Character device S_BLK Block device S_LNK Symbolic link S_FIFO Named pipe S_SOCK Socket type stats st_dev int Device number st_ino int Inode number st_kind file_kind Kind of the file st_perm file_perm Access rights st_nlink int Number of links st_uid int User id of the owner st_gid int Group id of the owner st_rdev int Device minor number st_size int Size in bytes st_atime float Last access time st_mtime float Last modification time st_ctime float Last status change time The informations returned by the stat calls 264 val stat string gt stats Return the information for the named file val lstat string gt stats Same as stat but in case the file is a symbolic link return the information for the link itself val fstat file_descr gt stats Return the information for the file associated with the give
330. so the children that receive stop signals val execv string gt string array gt unit execv prog args execute the program in file prog with the arguments args and the current process environment val execve string gt string array gt string array gt unit Same as execv except that the third argument provides the environment to the program executed val execvp string gt string array gt unit val execvpe string gt string array gt string array gt unit Same as execv and execvp respectively except that the program is searched in the path val fork unit gt int Fork a new process The returned integer is 0 for the child process the pid of the child process for the parent process val wait unit gt int process_status Wait until one of the children processes die and return its pid and termination status Chapter 18 The unix library Unix system calls 261 val waitpid wait_flag list gt int gt int process_status Same as wait but waits for the process whose pid is given A pid of 1 means wait for any child A pid of 0 means wait for any child in the same process group as the current process Negative pid arguments represent process groups The list of options indicates whether waitpid should return immediately without waiting or also report stopped children val system string gt process_status Execute the given command wait until it terminates and return its terminatio
331. spaces spaces are printed val print_flush unit gt unit Flush the pretty printer all opened boxes are closed and all pending text is displayed Chapter 17 The standard library 221 val print_newline unit gt unit Equivalent to print_flush followed by a new line val force_newline unit gt unit Force a newline in the current box Not the normal way of pretty printing you should prefer break hints val print_if_newline unit gt unit Execute the next formatting command if the preceding line has just been split Otherwise ignore the next formatting command Margin val set_margin int gt unit set_margin d sets the value of the right margin to d in characters this value is used to detect line overflows that leads to split lines Nothing happens if d is smaller than 2 or bigger than 999999999 val get_margin unit gt int Return the position of the right margin Maximum indentation limit val set_max_indent int gt unit set_max_indent d sets the value of the maximum indentation limit to d in characters once this limit is reached boxes are rejected to the left if they do not fit on the current line Nothing happens if d is smaller than 2 or bigger than 999999999 val get_max_indent unit gt int Return the value of the maximum indentation limit in characters Formatting depth maximum number of boxes allowed before ellipsis val set_max_boxes int gt unit set
332. spec end is the type of a class body It specifies its instance variables and methods In this type typexpr is match agains self type therefore provinding a binding for self type A class body will match a class body type if it provides definitions for all the components specified in the class type and these definitions meet the type requirements given in the class type Furthermore all methods either virtual or public present in the class body must also be present in the class type on the other hand some instance variables and concrete private methods may be omitted A virtual method will match a concrete method thus allowing to forget its implementation An immutable instance variable will match a mutable instance variable Inheritance The inheritance construct inherit class type allows to include methods and instance variables from other classes types The instance variable and method types from this class type are added into the current class type Instance variable specification A specification of an instance variable is written val mutable inst var name typexpr where inst var name is the name of the instance variable and typexpr its expected type The flag mutable indicates whether this instance variable can be physically modified An instance variable specification will hide any previous specification of an instance variable of the same name Method specification A specification of an method is written method private me
333. st letter capitalized as if the following definition was entered at top level module A sig contents of file a mli end struct contents of file a ml end The files defining the compilation units can be compiled separately using the ocaml c command the c option means compile only do not try to link this produces compiled interface files with extension cmi and compiled object code files with extension cmo When all units have been compiled their cmo files are linked together using the ocaml command For instance the following commands compile and link a program composed of two compilation units aux and main ocamlc c aux mli produces aux cmi ocamlc c aux ml produces aux cmo ocamlc c main mli produces main cmi ocamlc c main ml produces main cmo ocamlc o theprogram aux cmo main cmo The program behaves exactly as if the following phrases were entered at top level module Aux sig contents of aux mli end struct contents of aux ml end module Main sig contents of main mli end struct contents of main ml end In particular Main can refer to Aux the definitions and declarations contained in main ml and main mli can refer to definition in aux m1 using the Aux ident notation provided these definitions are exported in aux mli The order in which the cmo files are given to ocaml during the linking phase determines the order in which the module definitions o
334. standard library module Lexing The functions Lexing from_channel Lexing from_string and Lexing from_function create lexer buffers that read from an input channel a character string or any reading function respec tively See the description of module Lexing in chapter 16 When used in conjunction with a parser generated by ocamlyacc the semantic actions compute a value belonging to the type token defined by the generated parsing module See the description of ocamlyacc below 141 142 11 2 Syntax of lexer definitions The format of lexer definitions is as follows header let ident regexp rule entrypoint parse regexp action i genase regexp action and entrypoint parse and trailer Comments are delimited by and as in Caml 11 2 1 Header and trailer The header and trailer sections are arbitrary Caml text enclosed in curly braces Either or both can be omitted If present the header text is copied as is at the beginning of the output file and the trailer text at the end Typically the header section contains the open directives required by the actions and possibly some auxiliary functions used in the actions 11 2 2 Naming regular expressions Between the header and the entry points one can give names to frequently occurring regular expressions This is written let ident regexp In following regular expressions the identifier ident can be used as shorthand for regexp
335. stdout err_formatter formatter A formatter to use with formatting functions below for output to standard error It is defined as formatter_of_out_channel stderr formatter_of_buffer Buffer t gt formatter formatter_of_buffer b returns a new formatter writing to buffer b As usual the formatter has to be flushed at the end of pretty printing using pp_print_flush or pp_print_newline to display all the pending material In this case the buffer is also flushed using Buffer flush stdbuf Buffer t The string buffer in which str_formatter writes str_formatter formatter A formatter to use with formatting functions below for output to the stdbuf string buffer Chapter 17 The standard library 225 val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val val flush_str_formatter unit gt string Returns the material printed with str_formatter flushes the formatter and reset the corresponding buffer str_formatter is defined as formatter_of_buffer stdbuf make_formatter string gt int gt int gt unit gt unit gt unit gt formatter make_formatter out flush returns a new formatter that writes according to the output function out and the flushing function flush Hence a formatter to out channel oc is returned by make_formatter output oc fun gt flush oc pp_
336. strained signature The constraint module module path extended module path adds type equations to all type components of the sub structure denoted by module path making them equivalent to the corresponding type components of the structure denoted by extended module path For instance if the module type name S is bound to the signature sig type t module M sig type u end end then S with type t int denotes the signature sig type t int module M sig type u end end and S with module M N denotes the signature sig type t module M sig type u N u end end A functor taking two arguments of type S that share their t component is written functor A S B S with type t A t 5 11 Module expressions module implementations Module expressions are the module level equivalent of value expressions they evaluate to modules thus providing implementations for the specifications expressed in module types Chapter 5 The Objective Caml language 107 module expr module path struct definition end functor module name module type gt module expr module expr module expr module expr module expr module type definition let rec let binding and let binding external value name typexpr external declaration type definition exception definition class definition classtype definition module module name module name module type module type module expr module type modtype name modu
337. sts for structural equality of e1 and e2 Mutable structures e g references and arrays are equal if and only if their current contents are structurally equal even if the two mutable objects are not the same physical object Equality between functional values raises Invalid_argument Equality between cyclic data structures may not terminate lt gt a gt a gt bool Negation of lt a gt a gt bool gt a gt a gt bool lt a gt a gt bool gt a gt a gt bool Structural ordering functions These functions coincide with the usual orderings over integers characters strings and floating point numbers and extend them to a total ordering over all types The ordering is compatible with As in the case of mutable structures are compared by contents Comparison between functional values raises Invalid_argument Comparison between cyclic structures may not terminate compare a gt a gt int compare x y returns 0 if x y a negative integer if x lt y and a positive integer if x gt y The same restrictions as for apply compare can be used as the comparison function required by the Set and Map modules min a gt a gt a Return the smaller of the two arguments max a gt a gt a Return the greater of the two arguments a gt a gt bool e1 e2 tests for physical equality of e1 and e2 On integers and charact
338. supported Socket type not supported Operation not supported on socket Protocol family not supported Chapter 18 The unix library Unix system calls 259 EAFNOSUPPORT Address family not supported by protocol family EADDRINUSE Address already in use EADDRNOTAVAIL Can t assign requested address ENETDOWN Network is down ENETUNREACH Network is unreachable ENETRESET Network dropped connection on reset ECONNABORTED Software caused connection abort ECONNRESET Connection reset by peer ENOBUFS No buffer space available EISCONN Socket is already connected ENOTCONN Socket is not connected ESHUTDOWN Can t send after socket shutdown ETOOMANYREFS Too many references can t splice ETIMEDOUT Connection timed out ECONNREFUSED Connection refused EHOSTDOWN Host is down EHOSTUNREACH No route to host ELOOP Too many levels of symbolic links All other errors are mapped to EUNKNOWNERR EUNKNOWNERR of int Unknown error The type of error codes exception Unix_error of error string string Raised by the system calls below when an error is encountered The first component is the error code the second component is the function name the third component is the string parameter to the function if it has one or the empty string otherwise val error_message error gt string Retu
339. t gt int gt color Return the color of the given point moveto int gt int gt unit Position the current point current_point unit gt int int Return the position of the current point lineto int gt int gt unit Draw a line with endpoints the current point and the given point and move the current point to the given point draw_arc int gt int gt int gt int gt int gt int gt unit draw_arc x y rx ry al a2 draws an elliptical arc with center x y horizontal radius rx vertical radius ry from angle a1 to angle a2 in degrees The current point is unchanged draw_ellipse int gt int gt int gt int gt unit draw_ellipse x y rx ry draws an ellipse with center x y horizontal radius rx and vertical radius ry The current point is unchanged draw_circle int gt int gt int gt unit draw_circle x y r draws a circle with center x y and radius r The current point is unchanged set_line_width int gt unit Set the width of points and lines drawn with the functions above Under X Windows set_line_width 0 selects a width of 1 pixel and a faster but less precise drawing algorithm than the one used when set_line_width 1 is specified Chapter 22 The graphics library 305 Text drawing val draw_char char gt unit val draw_string string gt unit Draw a character or a character string with lower left corner at current position After drawing the current position is se
340. t x instead of Array set an x val make int gt a gt a array val create int gt a gt a array Array make n x returns a fresh array of length n initialized with x All the elements of this new array are initially physically equal to x in the sense of the predicate Consequently if x is mutable it is shared among all elements of the array and modifying x through one of the array entries will modify all other entries at the same time Raise Invalid_argument ifn lt 0 orn gt Sys max_array_length If the value of x isa floating point number then the maximum size is only Sys max_array_length 2 Array create is a deprecated alias for Array make Chapter 17 The standard library 213 val init int gt int gt a gt a array Array init n f returns a fresh array of length n with element number i initialized to the result of f i In other terms Array init n f tabulates the results of f applied to the integers O to n 1 val make_matrix int gt int gt a gt a array array val val val val val val val create_matrix int gt int gt a gt a array array Array make_matrix dimx dimy e returns a two dimensional array an array of arrays with first dimension dimx and second dimension dimy All the elements of this new matrix are initially physically equal to e The element x y of a matrix m is accessed with the notation m x y Raise Invalid_argument
341. t method get_offset int method virtual get_x int method virtual move int gt unit HH HH H H end class point x_init object inherit abstract_point x_init method get_x x method move d x lt x d 30 end class point int gt object val mutable x int method get_offset int method get_x int method move int gt unit end 2 5 Private methods Private methods are methods that do not appear in object interfaces They can only be invoked from other methods of the same object class restricted_point x_init object self val mutable x x_init method private move d x lt x d method bump self move 1 end class restricted_point int gt object val mutable x int method bump unit method get_x int method private move int gt unit end method get_x x let p new restricted_point 0 val p restricted_point lt obj gt p move 10 Characters 0 1 This expression has type restricted_point It has no method move p bump unit Private methods are inherited they are by default visible in subclasses unless they are hidden by signature matching as described below Private methods can be made public in a subclass class point_again x object self inherit restricted_point x method virtual move Chapter 2 Objects in Caml 31 end class point_again int gt object val mutable x int m
342. t to the lower right corner of the text drawn val set_font string gt unit val set_text_size int gt unit Set the font and character size used for drawing text The interpretation of the arguments to set_font and set_text_size is implementation dependent val text_size string gt int int Return the dimensions of the given text if it were drawn with the current font and size Filling val fill_rect int gt int gt int gt int gt unit fill_rect x y w h fills the rectangle with lower left corner at x y width w and height h with the current color val fill_poly int int array gt unit Fill the given polygon with the current color The array contains the coordinates of the vertices of the polygon val fill_arc int gt int gt int gt int gt int gt int gt unit Fill an elliptical pie slice with the current color The parameters are the same as for draw_arc val fill_ellipse int gt int gt int gt int gt unit Fill an ellipse with the current color The parameters are the same as for draw_ellipse val fill_circle int gt int gt int gt unit Fill a circle with the current color The parameters are the same as for draw_circle 306 Images type image val val val val val val val The abstract type for images in internal representation Externally images are represented as matrices of colors transp color In matrices of colors this
343. t_channel gt unit and apply it to outchan take no argument and output one character Refer to the C library printf function for the meaning of flags and field width specifiers If too few arguments are provided printing stops just before converting the first missing argument val printf a out_channel unit format gt a Same as fprintf but output on stdout val eprintf a out_channel unit format gt a Same as fprintf but output on stderr val sprintf a unit string format gt a Same as fprintf but instead of printing on an output channel return a string containing the result of formatting the arguments val bprintf Buffer t gt a Buffer t unit format gt a Same as fprintf but instead of printing on an output channel append the formatted arguments to the given extensible buffer see module Buffer 17 21 Module Queue first in first out queues This module implements queues FIFOs with in place modification type at The type of queues containing elements of type a Chapter 17 The standard library 245 exception Empty val val val val val val val Raised when take is applied to an empty queue create unit gt at Return a new queue initially empty add a gt a t gt unit add x q adds the element x at the end of the queue q take a t gt a take q removes and returns the first element in queue q or raises
344. te syntax which in the case of expressions is the familiar algebraic notation e g 2 x 1 For the printing function we take into account the usual precedence rules i e binds tighter than to avoid printing unnecessary parentheses To this end we maintain the current operator precedence and print parentheses around an operator only if its precedence is less than the current precedence let print_expr exp Local function definitions let open_paren prec op_prec if prec gt op_prec then print_string in let close_paren prec op_prec if prec gt op_prec then print_string in let rec print prec exp prec is the current precedence match exp with Const c gt print_float c Var v gt print_string v Sum f g gt open_paren prec 0 print 0 f print_string print 0 g close_paren prec 0 Diff f g gt open_paren prec 0 print 0 f print_string print 1 g close_paren prec 0 Prod f g gt open_paren prec 2 print 2 f print_string print 2 g close_paren prec 2 Quot f g gt open_paren prec 2 print 2 f print_string print 3 g close_paren prec 2 in print 0 exp val print_expr expression gt unit lt fun gt Chapter 1 The core language 21 let e Sum Prod Const 2 0 Var x Const 1 0 val e expression Sum Prod Const 2 Var x Const 1 print_expr e print_new
345. ted It then discards tokens from the input until it finds three suc cessive tokens that can be accepted and starts processing with the first of these If no state can be uncovered where the error token can be shifted then the parser aborts by raising the Parsing Parse_error exception Refer to documentation on yacc for more details and guidance in how to use error recovery 11 5 Options The ocamlyacc command recognizes the following options v Generate a description of the parsing tables and a report on conflicts resulting from ambigu ities in the grammar The description is put in file grammar output Chapter 11 Lexer and parser generators ocamllex ocamlyacc 147 bprefix Name the output files prefix ml prefix mli prefix output instead of the default naming convention 11 6 A complete example The all time favorite a desk calculator This program reads arithmetic expressions on standard input one per line and prints their values Here is the grammar definition File parser mly token lt int gt INT token PLUS MINUS TIMES DIV token LPAREN RPAREN token EOL left PLUS MINUS lowest precedence left TIMES DIV medium precedence Z nonassoc UMINUS highest precedence start main the entry point type lt int gt main Ah main expr EOL 1 expr INT 1 LPAREN expr RPAREN 2 expr PLUS expr 1 3 expr MINUS expr 1 3 expr TIMES expr 1 3 e
346. terface mli file for a file just redirect the standard output of the compiler to a mli file and edit that file to remove all declarations of unexported names I directory Add the given directory to the list of directories searched for compiled interface files cmi and compiled object code files cmo By default the current directory is searched first then the standard library directory Directories added with I are searched after the current directory in the order in which they were given on the command line but before the standard library directory impl filename Compile the file filename as an implementation file even if its extension is not ml intf filename Compile the file filename as an interface file even if its extension is not mli linkall Force all modules contained in libraries to be linked in If this flag is not given unreferenced modules are not linked in When building a library a flag setting the linkall flag forces all subsequent links of programs involving that library to link all the modules contained in the library make runtime Build a custom runtime system in the file specified by option o incorporating the C object files and libraries given on the command line This custom runtime system can be used later to execute bytecode executables produced with the ocamlc use runtime runtime name option See section 15 1 4 for more information 120 noassert Turn assertion checking off assert
347. th print_newline lt n gt print the following item as if it were of length n Hence printf lt 0 gt s arg is equivalent to print_as 0 arg If lt n gt is not followed by a conversion specification then the following character of the format is printed as if it were of length n print a plain character Example printf s d x 1 is equivalent to open_box print_string x print_space print_int 1 close_box It prints x 1 within a pretty printing box Chapter 17 The standard library 227 val bprintf Buffer t gt a formatter unit format gt a Same as fprintf but instead of printing on a formatter writes into the buffer argument val printf a formatter unit format gt a Same as fprintf but output on std_formatter val eprintf a formatter unit format gt a Same as fprintf but output on err_formatter val sprintf a unit string format gt a Same as printf but instead of printing on a formatter return a string containing the result of formatting the arguments 17 9 Module Gc memory management control and statistics type stat minor_words int promoted_words int major_words int minor_collections int major_collections int heap_words int heap_chunks int live_words int live_blocks int free_words int free_blocks int largest_free int fragments int compactions int The memory management
348. the code for adjustment is part of the definition of the class and will be inherited This ability provides class constructors as can be found in other languages Several constructors can be defined this way to build objects of the same class but with different initialization patterns an alternative is to use initializers as decribed below in section 2 3 2 2 Reference to self A method can also send messages to self that is the current object For that self must be explicitly bound here to the variable s s could be any identifier even though we will often choose the name self class printable_point x_init object s val mutable x x_init method get_x x method move d x lt x d method print print_int s get_x end class printable_point int gt object val mutable x int method get_x int method move int gt unit method print unit end let p new printable_point 7 val p printable_point lt obj gt p print 7 unit 0 Dynamically the variable s is bound at the invocation of a method In particular when the class printable_point will be inherited the variable s will be correctly bound to the object of the subclass 2 3 Initializers Let bindings within class definitions are evaluated before the object is constructed It is also possible to evaluate an expression immediately after the object has been built Such code is written as an anonymous hidden method called an
349. the function denoted by expr to the current stream then matches the result of the function against pattern Finally the component ident simply binds the identifier to the stream being matched Stream matching proceeds destructively once a component has been matched it is discarded from the stream by in place modification Stream matching proceeds in two steps first a pattern is selected by matching the stream against the first components of the stream patterns then the following components of the selected pattern are checked against the stream If the following components do not match the exception Stream Error is raised There is no backtracking here stream matching commits to the pattern selected according to the first element If none of the first components of the stream patterns match the exception Stream Failure is raised The Stream Parse_failure exception causes the next alternative to be tried if it occurs during the matching of the first element of a stream before matching has committed to one pattern The streams hold the count of their elements discarded The optional pattern before the first stream pattern is bound to the stream count before the matching The one after each stream pattern optional too is bound to the stream count after the matching The exception Parse_error has a string parameter coming from the optional expr after the stream pattern components its default is the empty string This expression is evaluat
350. the primitive taking native C values as arguments and returning a native C value The second function often called the stub code is a simple wrapper around the first function that converts its arguments from Caml values to C values call the first function and convert the returned C value to Caml value For instance here is the stub code for the input primitive value input value channel value buffer value offset value length return Val_long getblock struct channel channel amp Byte buffer Long_val offset Long_val length Here Val_long Long_val and so on are conversion macros for the type value that will be described later The hard work is performed by the function getblock which is declared as long getblock struct channel channel char p long n To write C code that operates on Objective Caml values the following include files are provided Include file Provides caml mlvalues h definition of the value type and conversion macros caml alloc h allocation functions to create structured Caml objects caml memory h miscellaneous memory related functions and macros for GC interface in place modification of structures etc caml fail h functions for raising exceptions see section 15 4 6 caml callback h callback from C to Caml see section 15 6 These files reside in the caml subdirectory of the Objective Caml standard library directory usually usr loca
351. thod name typexpr where method name is the name of the method and typexpr its expected type The flag private indicates whether the method can be accessed from outside the class Several specification for the same method must have compatible types Virtual method specification Virtual method specification is written method private virtual method name typexpr where method name is the name of the method and typexpr its expected type Chapter 5 The Objective Caml language 99 Constraints on type parameters The construct constraint typexpr typexpr forces the two type expressions to be equals This is typically used to specify type parameters they can be that way be bound to a specified type expression 5 9 2 Class expressions Class expressions are the class level equivalent of value expressions they evaluate to classes thus providing implementations for the specifications expressed in class types class expr class path typexpr typexpr class path class expr class expr class type class expr expr fun pattern gt class expr let rec let binding and let binding in class expr object pattern typexpr class field end class field inherit class expr as value name val mutable inst var name expr method private method name pattern expr method private virtual method name typexpr constraint typexpr typexpr initializer expr Simple class expressions The exp
352. tically On the other hand the function discount is given as such with no possibility for further personalization It is important that to provide the client s view as a functor Client so that client accounts can still be build after a possible specialization of the bank The functor Client may remain unchanged and be passed the new definition to initialize a client s view of the extended account module Investment_account M MONEY struct type m M c module A Account M class bank object inherit A bank as super method deposit x if mew M c 1000 leq x then print_string Would you like to invest super deposit x end module Client A Client end HH HH HH FH HOH FH OH OH HF OF OF The functor Client may also be redefined when some new features of the account can be given to the client module Internet_account M MONEY struct type m M c module A Account M class bank object inherit A bank Chapter 4 Advanced examples with classes and modules 63 method mail s print_string s end class type client_view object method deposit m gt unit method history m operation list method withdraw m gt m method balance m method mail string gt unit end module Client B sig class bank client_view end struct class account x client_view object inherit B bank inherit A check_client x end end HH HH HHH HHH HH H HH OF OH FH HHHH
353. ting functions e g print_int and print_string when the material for a box has been printed call close_box to close the box at the end of your routine evaluate print_newline to close all remaining boxes and flush the pretty printer The behaviour of pretty printing commands is unspecified if there is no opened pretty printing box Each box opened via one of the open_ functions below must be closed using close_box for proper formatting Otherwise some of the material printed in the boxes may not be output or may be formatted incorrectly In case of interactive use the system closes all opened boxes and flushes all pending text as with the print_newline function after each phrase Each phrase is therefore executed in the initial state of the pretty printer Boxes val open_box int gt unit open_box d opens a new pretty printing box with offset d This box is the general purpose pretty printing box Material in this box is displayed horizontal or vertical break hints inside the box may lead to a new line if there is no more room on the line to print the remainder of the box or if a new line may lead to a new indentation demonstrating the indentation of the box When a new line is printed in the box d is added to the current indentation val close_box unit gt unit Close the most recently opened pretty printing box 220 Formatting functions val print_string string gt unit print_string str
354. tion constr decl constr decl label decl label decl type params ident ident ident constr decl cconstr name neconstr name of typexpr label decl label name typexpr mutable Jabel name typexpr type constraint constraint ident typexpr 96 Type definitions are introduced by the type keyword and consist in one or several simple definitions possibly mutually recursive separated by the and keyword Each simple definition defines one type constructor A simple definition consists in a lowercase identifier possibly preceded by one or several type parameters and followed by an optional type equation then an optional type representation and then a constraint clause The identifier is the name of the type constructor being defined The optional type parameters are either one type variable ident for type constructors with one parameter or a list of type variables ident ident for type constructors with several parameters These type parameters can appear in the type expressions of the right hand side of the definition The optional type equation typexpr makes the defined type equivalent to the type expression typexpr on the right of the sign one can be substituted for the other during typing If no type equation is given a new type is generated the defined type is incompatible with any other type The optional type representation describes the data structure
355. tion let temporarily_set_reference ref newval funct let oldval ref in try ref newval let res funct in ref oldval res with x gt ref oldval raise x val temporarily_set_reference a ref gt a gt unit gt b gt b lt fun gt 1 7 Symbolic processing of expressions We finish this introduction with a more complete example representative of the use of Caml for symbolic processing formal manipulations of arithmetic expressions containing variables The following variant type describes the expressions we shall manipulate Chapter 1 The core language 19 type expression Const of float Var of string Sum of expression expression e1 e2 e2 Prod of expression expression el e2 Diff of expression expression el Quot of expression expression el e2 HH HH H HF OF a 2 type expression Const of float Var of string Sum of expression expression Prod of expression expression l l Diff of expression expression l Quot of expression expression We first define a function to evaluate an expression given an environment that maps variable names to their values For simplicity the environment is represented as an association list exception Unbound_variable of string exception Unbound_variable of string let rec eval env exp match exp with Const c gt c Var v gt
356. tion Mod1 f calls function Mod2 g and function Mod2 g calls function Modi f In this case no matter what permutations you perform on the command line the program will be rejected at link time Fixes e Put f and g in the same module e Parameterize one function by the other That is instead of having modi ml let f x Mod2 g mod2 m1 let gy Mod1 f define modi ml let f g x 2 8 wan mod2 m1 let rec g y Modi fg and link mod1 cmo before mod2 cmo e Use a reference to hold one of the two functions as in 124 modi ml let forward_g ref fun x gt failwith forward_g lt type gt let f x forward_g mod2 m1 let gy Modi f let _ Modi forward_g g This will not work if g is a polymorphic function however The external function fis not available This error appears when trying to link code that calls external functions written in C in default runtime mode As explained in chapter 15 such code must be linked in custom runtime mode Fix add the custom option as well as the C libraries and C object files that implement the required external functions Chapter 8 The toplevel system ocaml This chapter describes the toplevel system for Objective Caml that permits interactive use of the Objective Caml system through a read eval print loop In this mode the system repeatedly reads Caml phrases from the input then typechecks compile and evaluate them then
357. try List assoc v env with Not_found gt raise Unbound_variable v Sum f g gt eval env f eval env g Diff f g gt eval env f eval env g Prod f g gt eval env f eval env g Quot f g gt eval env f eval env g val eval string float list gt expression gt float lt fun gt HH H OH H OF eval x 1 0 y 3 14 Prod Sum Var x Const 2 0 Var y float 9 42 Now for a real symbolic processing we define the derivative of an expression with respect to a variable dv let rec deriv exp dv match exp with Const c gt Const 0 0 Var v gt if v dv then Const 1 0 else Const 0 0 Sum f g gt Sum deriv f dv deriv g dv Diff f g gt Diff deriv f dv deriv g dv Prod f g gt Sum Prod f deriv g dv Prod deriv f dv g Quot f g gt Quot Diff Prod deriv f dv g Prod f deriv g dv Prod g g 55 val deriv expression gt string gt expression lt fun gt 20 deriv Quot Const 1 0 Var x x expression Quot Diff Prod Const 0 Var x Prod Const 1 Const 1 Prod Var x Var x 1 8 Pretty printing and parsing As shown in the examples above the internal representation also called abstract syntax of expres sions quickly becomes hard to read and write as the expressions get larger We need a printer and a parser to go back and forth between the abstract syntax and the concre
358. type socket_domain h_addr_list inet_addr array Structure of entries in the hosts database type protocol_entry p_name string p_aliases string array p_proto int Structure of entries in the protocols database type service_entry s_name string s_aliases string array S_port int s_proto string Structure of entries in the services database val gethostname unit gt string Return the name of the local host val gethostbyname string gt host_entry Find an entry in hosts with the given name or raise Not_found val gethostbyaddr inet_addr gt host_entry Find an entry in hosts with the given address or raise Not_found val getprotobyname string gt protocol_entry Find an entry in protocols with the given name or raise Not_found 276 val getprotobynumber int gt protocol_entry Find an entry in protocols with the given protocol number or raise Not_found val getservbyname string gt string gt service_entry Find an entry in services with the given name or raise Not_found val getservbyport int gt string gt service_entry Find an entry in services with the given service number or raise Not_found Terminal interface The following functions implement the POSIX standard terminal interface They provide control over asynchronous communication ports and pseudo terminals Refer to the termios man page for a complete description type terminal_io
359. type foo The type of this expression t contains type variables that cannot be generalized Type variables a b in a type t can be in either of two states generalized which means that the type tis valid for all possible instantiations of the variables and not gener alized which means that the type tis valid only for one instantiation of the variables In a let binding let name expr the type checker normally generalizes as many type variables as possible in the type of expr However this leads to unsoundness a well typed program can crash in conjunction with polymorphic mutable data structures To avoid this general ization is performed at let bindings only if the bound expression expr belongs to the class of syntactic values which includes constants identifiers functions tuples of syntactic values etc In all other cases for instance expr is a function application a polymorphic mutable could have been created and generalization is therefore turned off Non generalized type variables in a type cause no difficulties inside a given structure or compilation unit the contents of a ml file or an interactive session but they cannot be Chapter 7 Batch compilation ocamlc 123 allowed inside signatures nor in compiled interfaces cmi file because they could be used inconsistently later Therefore the compiler flags an error when a structure or compilation unit defines a value name whose type contains non
360. ually 0 to indicate no errors and a small positive integer to indicate failure An implicit exit 0 is performed each time a program terminates normally but not if it terminates because of an uncaught exception val at_exit unit gt unit gt unit Register the given function to be called at program termination time The functions registered with at_exit will be called when the program executes exit They will not be called if the program terminates because of an uncaught exception The functions are called in last in first out order the function most recently added with at_exit is called first Chapter 17 The standard library This chapter describes the functions provided by the Caml Light standard library The modules from the standard library are automatically linked with the user s object code files by the ocamlc command Hence these modules can be used in standalone programs without having to add any cmo file on the command line for the linking phase Similarly in interactive use these globals can be used in toplevel phrases without having to load any cmo file in memory Unlike the Pervasive module from the core library the modules from the standard library are not automatically opened when a compilation starts or when the toplevel system is launched Hence it is necessary to use qualified identifiers to refer to the functions provided by these modules or to add open directives Conventions For easy refere
361. ule types The expression modtype path is equivalent to the module type bound to the name modtype path The expression module type denotes the same type as module type 5 10 2 Signatures Signatures are type specifications for structures Signatures sig end are collections of type specifications for value names type names exceptions module names and module type names A structure will match a signature if the structure provides definitions implementations for all the names specified in the signature and possibly more and these definitions meet the type requirements given in the signature For compatibility with Caml Light an optional is allowed after each specification in a signature The has no semantic meaning Value specifications A specification of a value component in a signature is written val value name typexpr where value name is the name of the value and typexpr its expected type 104 The form external value name typexpr external declaration is similar except that it requires in addition the name to be implemented as the external function specified in external declaration see chapter 15 Type specifications A specification of one or several type components in a signature is written type typedef and typedef and consists of a sequence of mutually recursive definitions of type names Each type definition in the signature specifies an optional type equation typexp and an optional type representati
362. ument to ocamlrun either does not exist or is not a valid executable bytecode file Truncated bytecode file The file that ocamlrun is trying to execute is not a valid executable bytecode file Probably it has been truncated or mangled since created Erase and rebuild it Uncaught exception The program being executed contains a stray exception That is it raises an exception at some point and this exception is never caught This causes immediate termination of the program The name of the exception is printed but not its arguments Out of memory The program being executed requires more memory than available Either the program builds excessively large data structures or the program contains too many nested function calls and the stack overflows In some cases your program is perfectly correct it just requires more memory than your machine provides In other cases the out of memory message reveals an error in your program non terminating recursive function allocation of an excessively large array or string attempts to build an infinite list or other data structure To help you diagnose this error run your program with the v option to ocamlrun If it displays lots of Growing stack messages this is probably a looping recursive function If it displays lots of Growing heap messages with the heap size growing slowly this is probably an attempt to construct a data structure with too many infinitely many
363. under the interactive toplevel system ocam1 os_type string Operating system currently executing the Caml program One of Unix Win32 or MacOS word_size int Size of one word on the machine currently executing the Caml program in bits 32 or 64 max_string_length int Maximum length of a string max_array_length int Maximum length of an array Chapter 17 The standard library 255 Signal handling type signal_behavior val val val val val val val val val val val val val val val val val val val val val val val Signal_default Signal_ignore Signal_handle of int gt unit What to do when receiving a signal Signal_default take the default behavior usually abort the program Signal_ignore ignore the signal Signal_handle f call function f giving it the signal number as argument Signal int gt signal_behavior gt signal_behavior Set the behavior of the system on receipt of a given signal The first argument is the signal number Return the behavior previously associated with the signal set_signal int gt signal_behavior gt unit Same as signal but return value is ignored sigabrt int Abnormal termination sigalrm int Timeout sigfpe int Arithmetic exception sighup int Hangup on controlling terminal sigill int Invalid hardware instruction sigint int Interactive interrupt ctrl C sigkill int Termination cannot be i
364. unit Reposition the descriptor to the beginning of the directory val closedir dir_handle gt unit Close a directory descriptor Pipes and redirections val pipe unit gt file_descr file_descr Create a pipe The first component of the result is opened for reading that s the exit to the pipe The second component is opened for writing that s the entrance to the pipe val mkfifo string gt file_perm gt unit Create a named pipe with the given permissions High level process and redirection management val create_process string gt string array gt file_descr gt file_descr gt file_descr gt int create_process prog args new_stdin new_stdout new_stderr forks a new process that executes the program in file prog with arguments args The pid of the new process is returned immediately the new process executes concurrently with the current process The standard input and outputs of the new process are connected to the descriptors new_stdin new_stdout and new_stderr Passing e g stdout for new_stdout prevents the redirection and causes the new process to have the same standard output as the current process The executable file prog is searched in the path The new process has the same environment as the current process All file descriptors of the current process are closed in the new process except those redirected to standard input and outputs val create_process_env string gt string array gt string a
365. unit method times float gt a Chapter 2 Objects in Caml end 47 Here the representation of the object is known only to a particular object To make it available to other objects of the same class we are forced to make it available to the whole world However we can easily restrict the visibility of the representation using the module system module type MONEY HH HHH H HHH HHH FH HHH H HHH H OH OF sig type t class c object a module Euro struct float val repr t method value method print method times method leq method plus end end MONEY type t float class c x object self val repr x method value method print method times method leq p method plus end end gt t unit float gt a a gt bool a gt a 2a repr print_float repr k lt repr k x gt a repr lt p value p a lt repr x p value gt Another example of friend functions may be found in section 4 2 3 These examples occur when a group of objects here objects of the same class and functions should see each others internal representation while their representation should be hidden from the outside The solution is always to define all friends in the same module give access to the representation and use a signature constraint to make the representation abstract outside of the module 48 Chapter 3 Th
366. ure v string_length v returns the length number of characters of the string v Byte v n returns the nt character of the string v with type char Characters are num bered from 0 to string_length v 1 Byte_u v n returns the n character of the string v with type unsigned char Characters are numbered from 0 to string_length v 1 String_val v returns a pointer to the first byte of the string v with type char This pointer is a valid C string there is a null character after the last character in the string However Caml strings can contain embedded null characters that will confuse the usual C functions over strings Double_val v returns the floating point number contained in value v with type double Double_field v n returns the n element of the array of floating point numbers v a block tagged Double_array_tag Store_double_field v n d stores the double precision floating point number d in the nt element of the array of floating point numbers v The expressions Field v n Byte v n and Byte_u v n are valid l values Hence they can be assigned to resulting in an in place modification of value v Assigning directly to Field v n must be done with care to avoid confusing the garbage collector see below Chapter 15 Interfacing C with Objective Caml 177 15 4 4 Allocating blocks Simple interface Atom t returns an atom zero sized block with tag t Zero sized blocks are preallocated
367. val val val val val get_normalize_ratio_when_printing unit gt bool set_normalize_ratio_when_printing bool gt unit Get or set the flag normalize_ratio_when_printing When on rational numbers are normalized before being printed When off rational numbers are printed as is without normalization Initially on get_approx_printing unit gt bool set_approx_printing bool gt unit Get or set the flag approx_printing When on rational numbers are printed as a decimal approximation When off rational numbers are printed as a fraction Initially off get_floating_ precision unit gt int set_floating precision int gt unit Get or set the parameter floating_precision This parameter is the number of digits displayed when approx_printing is on Initially 12 286 Chapter 20 The str library regular expressions and string processing The str library provides high level string processing functions some based on regular expressions It is intended to support the kind of file processing that is usually performed with scripting languages such as awk perl or sed Programs that use the str library must be linked in custom runtime mode as follows ocamlc custom other options str cma other files cclib lstr ocamlopt other options str cmxa other files cclib lstr For interactive use of the str library do ocamlmktop custom o mytop str cma cclib lstr mytop 20 1 Module Str regular expres
368. value method Considering m of type comparable would allow to call method leq on m with an argument that does not have a method value which would be an error Similarly the type money2 below is not a subtype of type money class money2 x object inherit money x method times k lt repr k repr gt end class money2 float gt object a val repr float method leq a gt bool method times float gt a method value float end It is however possible to define functions that manipulate objects of type either money or money2 the function min will return the minimum of any two objects whose type unifies with comparable The type of min is not the same as comparable gt comparable gt comparable as the abbreviation comparable hides a type variable an ellipsis Each occurrence of this abbreviation generates a new variable let min x comparable y if x leq y then x else y val min comparable as a gt a gt a lt fun gt This function can be applied to objects of type money or money2 min new money 1 3 new money 3 1 value float 1 3 min new money2 5 0 new money2 3 14 value float 3 14 More examples of binary methods can be found in sections 4 2 1 and 4 2 3 46 Notice the use of functional update for method times Writing new money2 k repr instead of lt repr k repr gt would not behave well with inh
369. ver hashing Hashing performs a depth first right to left traversal of the structure x stopping after n meaningful nodes were encountered or m nodes meaningful or not were encountered Meaningful nodes are integers floating point numbers strings characters booleans and constant constructors Larger values of m and n means that more nodes are taken into account to compute the final hash value and therefore collisions are less likely to happen However hashing takes longer The parameters m and n govern the tradeoff between accuracy and speed 17 12 Module Lazy deferred computations type a status Delayed of unit gt a Value of a Exception of exn type a t a status ref A value of type a Lazy t is a deferred computation also called a suspension that computes a result of type a The expression lazy expr returns a suspension that computes expr val force a t gt a Lazy force x computes the suspension x and returns its result If the suspension was already computed Lazy force x returns the same value again If it raised an exception the same exception is raised again 17 13 Module Lexing the run time library for lexers generated by ocamllex Lexer buffers type lexbuf refill_buff lexbuf gt unit mutable lex_buffer string mutable lex_buffer_len int mutable lex_abs_pos int mutable lex_start_pos int mutable lex_curr_pos int mutable lex_last_pos int
370. wait_read and wait_write but wait for at most the amount of time given as second argument in seconds Return true if the file descriptor is ready for input output and false if the timeout expired val select Unix file_descr list gt Unix file_descr list gt Unix file_descr list gt float gt Unix file_descr list Unix file_descr list Unix file_descr list Suspend the execution of the calling thead until input output becomes possible on the given Unix file descriptors The arguments and results have the same meaning as for Unix select val wait_pid int gt int Unix process_status wait_pid p suspends the execution of the calling thread until the Unix process specified by the process identifier p terminates A pid p of 1 means wait for any child A pid of 0 means wait for any child in the same process group as the current process Negative pid arguments represent process groups Returns the pid of the child caught and its termination status as per Unix wait val wait_signal int list gt int wait_signal sigs suspends the execution of the calling thread until the process receives one of the signals specified in the list sigs It then returns the number of the signal received Signal handlers attached to the signals in sigs will not be invoked Do not call wait_signal concurrently from several threads on the same signals 296 21 2 Module Mutex locks for mutual exclusion Mutexes mutual exclusion locks are used to
371. words major_words promoted_words Multiply by the word size 4 on a 32 bit machine 8 on a 64 bit machine to get the number of bytes type control mutable minor_heap_size int mutable major_heap_increment int mutable space_overhead int mutable verbose int mutable max_overhead int mutable stack_limit int The GC parameters are given as a control record The fields are minor_heap_size The size in words of the minor heap Changing this parameter will trigger a minor collection Default 32k major_heap_increment The minimum number of words to add to the major heap when increasing it Default 62k space_overhead The major GC speed is computed from this parameter This is the memory that will be wasted because the GC does not immediatly collect unreachable objects It is expressed as a percentage of the memory used for live data The GC will work more use more CPU time and collect objects more eagerly if space_overhead is smaller The computation of the GC speed assumes that the amount of live data is constant Default 42 max_overhead Heap compaction is triggered when the estimated amount of free memory is more than max_overhead percent of the amount of live data If max_overhead is set to 0 heap compaction is triggered at the end of each major GC cycle this setting is intended for testing purposes only If max_overhead gt 1000000 compaction is never triggered Default 1000000 verbose Th
372. write profile information when the program is executed The profile information can then be examined with the analysis program gprof See chapter 14 for more information on profiling The p option must be given both at compile time and at link time Linking object files not compiled with p is possible but results in less precise profiling 138 Unix See the Unix manual page for gprof 1 for more information about the pro files Full support for gprof is only available for certain platforms currently Intel x86 Linux and Alpha Digital Unix On other platforms the p option will result in a less precise profile no call graph information only a time profile Windows The p option does not work under Windows pp command Cause the compiler to call the given command as a preprocessor for each source file The output of command is redirected to an intermediate file which is compiled If there are no compilation errors the intermediate file is deleted afterwards The name of this file is built from the basename of the source file with the extension ppi for an interface m1i file and ppo for an implementation m1 file rectypes Allow arbitrary recursive types during type checking By default only recursive types where the recursion goes through an object type are supported S Keep the assembly code produced during the compilation The assembly code for the source file x ml1 is saved in the file z s thread Compile or
373. xpr DIV expr 1 3 MINUS expr prec UMINUS 2 Here is the definition for the corresponding lexer File lexer ml1l open Parser The type token is defined in parser mli exception Eof rule token parse DNE token lexbuf skip blanks l P p EOL 0 9 INT int_of_string Lexing lexeme lexbuf o PLUS i MINUS 148 2 TIMES l DIV EEG LPAREN Ie 298 RPAREN eof raise Eof Here is the main program that combines the parser with the lexer File calc ml let _ try let lexbuf Lexing from_channel stdin in while true do let result Parser main Lexer token lexbuf in print_int result print_newline flush stdout done with Lexer Eof gt exit 0 To compile everything execute ocamllex lexer mll generates lexer ml ocamlyacc parser mly generates parser ml and parser mli ocamlc c parser mli ocamlc c lexer ml ocamlc c parser ml ocamlc c calc ml ocamlc o calc lexer cmo parser cmo calc cmo 11 7 Common errors ocamllex transition table overflow automaton is too big The deterministic automata generated by ocamllex are limited to at most 32767 transitions The message above indicates that your lexer definition is too complex and overflows this limit This is commonly caused by lexer definitions that have separate rules for each of the alphabetic keywords of the language as in the following example rule
374. y unsafe Turn bound checking off on array and string accesses the v i and s i constructs Programs compiled with unsafe are therefore slightly faster but unsafe anything can happen if the program accesses an array or string outside of its bounds use runtime runtime name Generate a bytecode executable file that can be executed on the custom runtime system runtime name built earlier with ocamlc make runtime runtime name See section 15 1 4 for more information yv Print the version number of the compiler w warning list Enable or disable warnings according to the argument warning list The argument is a string of one or several characters with the following meaning for each character A a enable disable all warnings F f enable disable warnings for partially applied functions i e f x expr where the appli cation f x has a function type Chapter 7 Batch compilation ocamlc 121 M m enable disable warnings for overriden methods P p enable disable warnings for partial matches missing cases in pattern matchings S s enable disable warnings for statements that do not have type unit e g exprl expr2 when ezpr1 does not have type unit U u enable disable warnings for unused redundant match cases V v enable disable warnings for hidden instance variables X x enable disable all other warnings The default setting is w A all warnings enabled 7 3 Modules and the file system This short section is inte
375. ype type type type type type type type string The type of character strings float The type of floating point numbers bool The type of booleans truth values unit The type of the unit value exn The type of exception values a array The type of arrays whose elements have type a a list of a a list The type of lists whose elements have type a a option None Some of a The type of optional values Ca b c format The type of format strings a is the type of the parameters of the format c is the result type for the printf style function and b is the type of the first argument given to a and t printing functions see module Printf Exceptions val raise exn gt a exception Match_failure of string int int Raise the given exception value Exception raised when none of the cases of a pattern matching apply The arguments are the location of the pattern matching in the source code file name position of first character position of last character Chapter 16 The core library 195 exception Assert_failure of string int int Exception raised when an assertion fails The arguments are the location of the pattern matching in the source code file name position of first character position of last character exception Invalid_argument of string Exception raised by library functions to signal that the given argument
376. ype class ref 7a gt Chapter 2 Objects in Caml 35 object val mutable x a method get a method set a gt unit end The method get has type a where a is unbound The reason is that at least one of the methods has a polymorphic type here the type of the value stored in the reference cell thus the class should be parametric or the method type should be constrained to a monomorphic type A monomorphic instance of the class could be defined by class ref x_init int object val mutable x x_init method get x method set y x lt y end class ref int gt object val mutable x int method get int method set int gt unit end HH H H A class for polymorphic references must explicitly list the type parameters in its declaration Class type parameters are always listed between and The type parameters must also be bound somewhere in the class body by a type constraint class a ref x_init object val mutable x x_init a method get x method set y x lt y end class a ref a gt object val mutable x a method get a method set a gt unit end HH H H let r new ref 1 in r set 2 r get int 2 The type parameter in the declaration may actually be constrained in the body of the class def inition In the class type the actual value of the type parameter is displayed in the constraint clause class a ref_succ

The Objective Caml system release 2.04 - The Caml language

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