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Barry's Prolog Reference Manual & User Guide

1. p_to_s_graph a b b c c d a c S s_to_p_graph S P S a b c b c c d d P a b a c b c c d yes Errors None See also s_to_p_graph 2 7 1 4 p_transpose 2 Synopsis p_transpose G1 G2 Description This predicate takes a graph G1 in P representation transposes that graph and unifies G2 with the result in P representation Examples p_transpose a b b c c d a c S S b a c b d c c a yes 250 CHAPTER 7 THE GRAPHS LIBRARY Errors None See also s_transpose 2 7 1 5 s_member 3 Synopsis s_member V1 V2 G Description Succeeds if there is an edge from vertex V1 to vertex V2 in the graph G which is given in S representation Examples p_to_s_graph a b b c S s_member V1 V2 S S a b b c c Vi a V2 b s a b b c c 1 Vi V2 c no Errors None See also p_member 3 7 1 6 s_to_p_graph 2 Synopsis s_to_p_graph S P 7 1 PREDICATES 251 Description This predicate takes a graph S in S representation and unifies P with the equivalent P representation graph Examples p_to_s_graph a b b c c d a c S s_to_p_graph S P a b c b c c d d a b a c b c c d UW Nn oul yes Errors None See also p_to_s_graph 2 7 1 7 s_to_p_trans 2 Synopsis s_to_p_trans S P Description This predicate takes a graph S in S representation tr
2. 157 4 1 167private_procedure l 158 4 1 168procedure_property 2 159 4 11 169proleg lexical digit I corr KES 159 4 1 170 prolog_lexical_letter 1 160 4 1 171 prolog_lexical_lower_case_letter 1 161 41 172 prolog_ lexical symbol 1 i ee c a go 88244 161 4 1 173 prolog_lexical_upper_case_letter 1 162 4 1 174prolog_lexical_W8 l o ee coos Tioga e he 163 vili CONTENTS aL 175prompt i cecs iseni EEE HH ER itea 163 4 1 176 public_procedure 1 a osoa 164 CI Ue MM 165 ALIAS Dre 2 e ea e A e de y e e 165 ayo pe ebar E e ke acea A ek ee PR Se De e 166 cl dl nos a Soe eo ee oe eee haw 167 41 181 ppt e0de 1 ws ae So ee a Oh ee 168 AV VO2 PGE code 2 e oi ue ae Re he 168 4 1183 query_class 5 2 124 4 66 Pe RES So wee 169 Al Peo query imput 3d isos sir bo ae ad kw wm A 170 4A 1 185query_map 4 o 171 4 1 186query_read_line 2 o 172 LASER e E A A ote SS 172 LL IBSEN oc ee ke See ee Ye o ee 173 4 Tee read term 2 cocoa peue baw a eee 173 4 1 190 mead Germs csee ae be be dad ES 174 A VIGbMecenenlt 1 s oas la hae da ee ee a 176 A Lerepeat O0 ociosos Se RE dakie ES 177 A LIS retractile e eae ee eae a ee eo 177 A lL MWaretractall 1 seca Ra eR eee Re A LRG e 178 a A 179 ALIS cor E ds 180 e roar A A ee eee Gh a amp 181 A TAGS SEU SORE POEs Enis edo eck be yore bE YR ee DA oS 182 41 190 set prolog flag 2 o ca eca net uaa
3. L 2 270 CHAPTER 8 THE LISTS LIBRARY L 1 h no Errors None See also subseq1 2 8 1 23 subseq1 2 Synopsis subseqi L1 L2 Description Succeeds if the list L2 is a proper sub sequence of the list L1 Examples subseq1 1 2 L L 2 L L 1 no Errors None See also subseq0 2 8 1 PREDICATES 271 8 1 24 sumlist 2 Synopsis sumlist L S Description Succeeds if the sum of all of the elements of the list L is a equal to S Examples sumlist 1 2 3 S Ss 6 yes sumlist S S 0 yes Errors Since the elements of the list are evaluated errors may be thrown by eval 2 See also None 272 CHAPTER 8 THE LISTS LIBRARY Chapter 9 The ordset library The predicates in this library implement a set data type using sorted lists ordered according to 0 lt 2 To use the predicates in this library you will need to load the ordset fasl file One way to do this is with the following call ensure_loaded runtime ordset The advantage with ordered sets is that certain operations take much fewer instructions As an example consider the insertion of an element E1 into an ordered set when comparing E1 to each element of the list to avoid having duplicate entries we know that as soon as we find an element E2 in the list such that E20 gt E1 we have compared all of the elements we need to 9 1 Predica
4. yes add_file_search_path backup_logging dir logging_dir backups yes file_search_path backup_logging dir D D usr local logs backups yes Errors None See also add_file_search_path 2 4 1 95 findall 3 Synopsis findall Template Goal Bag Description Similar to bagof 3 but with the following exceptions e Should Goal be unsatisfiable finda11 3 does not fail as bagof 3 does Instead Bag is unified with the empty list Bag e Any uninstantiated variables free in Goal and not in Template are automatically existentially quantified This means finda11 3 does not enumerate solutions for these variables as bagof 3 does Examples bagof X member X Y 1 2 3 4 5 6 L X _521856 Y 2 L Tie 3 102 CHAPTER 4 BUILT IN PREDICATES Ps Il _521856 4 L 3 lt J Ps Il _521856 Y 6 5 E gt Il no findall X member X Y 1 2 3 4 5 6 L _522304 _525584 1 3 5 HR K ll yes bagof nothing fail Bag no findall nothing fail Bag Bag yes Errors instantiation_error The argument Goal was not instantiated type_error callable Goal The argument Goal was not callable type_error list Bag The argument Bag was neither uninstantiated nor a list See also bagof 3 4 1 96 float 1 Synopsis float T Description Succeeds if T is a floating point number 4 1 PREDICAT
5. yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error Either the argument L or the argument Alpha was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L and the argument Alpha are evalu ated errors may be thrown by eval 2 See also None 13 1 11 sample_absolute_deviation 3 Synopsis sample_absolute_deviation L C Result Description Result is the arithmetic mean of the absolute deviations of the members of the list of numbers L from the value C The value C should be some central value e g the mean or median of L 320 CHAPTER 13 THE STATISTICS LIBRARY Examples L 1 2 3 4 5 6 7 8 9 10 sample_arithmetic_mean L Mean sample_absolute_deviation L Mean D L 1 2 3 4 5 6 7 8 9 10 Mean 5 5 D 2 5 yes L 1 2 3 4 5 6 7 8 9 10 sample_median L Median sample_absolute_deviation L Median D L 1 2 3 4 5 6 7 8 9 10 Median 5 0 D 2 5 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error Either the argument L or the the argument C was an uninstantiated variable type_error list L The argument L was not a list Also as the argument C and the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_mean_absolute_deviation 2 sample_median_abs
6. yes Errors domain_error not_less_than_zero S The argument S was less than 0 instantiation_error At least one of the arguments X M or S was an unin stantiated variable Also as the arguments X M and S are evaluated errors may be thrown by eval 2 318 CHAPTER 13 THE STATISTICS LIBRARY See also None 13 1 9 normal_quantile 4 Synopsis normal_quantile P M S Zp Description Zp is the P quantile 0 lt P P lt 1 of the normal distribution with mean M and variance S Examples normal_quantile 0 9 70 16 Zp Zp 75 126915 yes Errors domain_error not_greater_than_one P The argument P was greater than 1 domain_error not_less_than_zero N Either the argument P or the ar gument S was less than 0 instantiation_error At least one of the arguments X M or S was an unin stantiated variable Also as the arguments P M and S are evaluated errors may be thrown by eval 2 See also None 13 1 10 population_mean_confidence_interval 4 Synopsis population_mean_confidence_interval L Alpha Low High 13 1 PREDICATES 319 Description This predicate calculates confidence interval Low High with significance level Alpha of the list of numbers L This means that the population mean lies within Low High with a probability of 1 Alpha Examples population_mean_confidence_interval 1 2 3 4 5 6 7 8 9 10 0 5 Low High Low 4 827195 High 6 172805
7. is_upper 0 c no is_upper 0 C yes Errors As Code is evaluated errors may be thrown by eval 2 See also None 12 1 17 read_line 1 Synopsis read_line Codes 303 304 CHAPTER 12 THE READSENT LIBRARY Description This predicate behaves as if it were defined as follows read_line Codes current_input Stream read_line Stream Codes Examples See read_line 2 Errors See read_line 2 See also read_line 2 12 1 18 read_line 2 Synopsis read_line Stream Codes Description Reads a list of character codes Codes from Stream until the newline code ASCII 10 is seen Note that Codes contains the newline code This predicate behaves as if it were defined as follows read_line Stream Codes is_newline Newline read_until Stream Newline Codes Examples read_line Codes 123 foo Codes 49 50 51 32 102 111 111 10 7 yes Errors See read_until 2 12 1 PREDICATES See also is_newline 1 read_until 2 12 1 19 read_sent 1 Synopsis read_sent Words Description Behaves as if it were defined as read_sent Words current_input Stream read_sent Stream Words Examples See read_sent 2 Errors See read_sent 2 See also read_sent 2 12 1 20 read_sent 2 Synopsis read_sent Stream Words Description 305 This predicate will read character codes from Stream until a code represent ing ei
8. This is information yes 2 4 Loading Prolog Files You can load files of Prolog code with the predicates consult 1 reconsult 1 ensure_loaded 1 and 2 See the manual pages for these predicates to find out which one suits your needs Each of the loading methods will pro cess directives which allow you to control the loading process The rest of this section describes these directives 2 4 1 discontiguous 1 The argument to this directive is a predicate indicator a sequence of predi cate indicators separated by 2 or a list of predicate indicators This directive informs the system that the procedures indicated by the predicate indicators may be declared by a sequence of discontiguous clauses This will prevent any warning messages being displayed See the documentation for the Prolog flag discontiguous_clauses_warnings for more information This indicator has no effect outside the file it is defined unless the file is included in another file Example discontiguous foo 1 2 4 2 dynamic 1 This is defined by the ISO standard but has no meaning when loading in Barry s Prolog The compiler on the other hand will process this directive See Chapter 15 for more information Example dynamic foo 1 6 CHAPTER 2 USING BARRY S PROLOG 2 4 3 ensure_loaded 1 This has the effect of calling ensure_loaded 1 as soon as the directive has been read This means that the loading of the current file may be p
9. domain_error not_less_than_zero Length The argument Length was an integer less than zero type_error atom Atom The argument Atom was not an atom type_error atom SubAtom The argument SubAtom was not an atom type_error integer After The argument After was not an integer type_error integer Before The argument Before was not an integer type_error integer Length The argument Length was not an integer 198 See also atom_index 3 atom_length 2 4 1 214 subsumes_chk 2 Synopsis subsumes_chk T1 T2 Description Same as subsumes_term 2 Examples See subsumes_term 2 Errors See subsumes_term 2 See also subsumes_term 2 4 1 215 subsumes_term 2 Synopsis subsumes_term T1 T2 Description CHAPTER 4 BUILT IN PREDICATES Succeeds if there is a substitution that when applied to T1 unifies it with T2 The variables of T1 are not bound Examples subsumes_term foo A B foo 1 2 A _524592 B _525456 yes Errors None 4 1 PREDICATES 199 See also None 4 1 216 system_error 0 Synopsis system_error Description Exits the Prolog system with a system error code Examples None Errors None See also None 4 1 217 Term comparison Synopsis L R L R L lt R L lt R L gt R L gt R Description These predicates compare the terms L and R with respect to the term order ing Term ordering is defined a
10. 308 CHAPTER 12 THE READSENT LIBRARY See also read_until 3 12 1 24 read_until 3 Synopsis read_until Stream Delimiters Codes Description Reads a list of character codes Codes from Stream until one of the codes in the list Delimiters is seen The character code 1 which represents an end of file is always considered to be a delimiter Note Codes contains the delimiter code Examples current_input S read_until S 13 10 Codes Hello S stream 0 Codes 72 101 108 108 111 10 yes Errors See get_code 2 See also None 12 1 25 trim_blanks 2 Synopsis trim_blanks Codes TrimmedCodes Description Removes all leading and trailing layout character codes in Codes and unifies the result with TrimmedCodes Here a layout character code is defined by is_layout 1 12 1 PREDICATES Examples trim_blanks 123 4 Trimmed Trimmed 49 50 51 32 52 yes Errors See is_layout 1 See also is_layout 1 309 310 CHAPTER 12 THE READSENT LIBRARY Chapter 13 The statistics library The predicates in this library implement common statistics functions To use these predicates you will need to load the statistics fasl file One way to do this is with the following call ensure_loaded runtime statistics 13 1 Predicates 13 1 1 chi_squared_cdf 3 Synopsis chi_squared_cdf X N Answer Description Answer is the probability that Y lt X
11. CONTENTS vil ALIS TNeme 2 isidro rasa 130 ALISO AAA 130 Mae abs Bi e e Bae si e 131 AD A343 numbers ooo a Ee 132 Ad loo munbervars S s o cos E e Soke Geen h ee Ee 132 a 6 on ee eee ee oe ae 134 a o oe Be tok e A ee Be 134 AW TSSWGHOKS a da od a e RR oe 135 4 1 1389number_base_codes 3 136 A 1 lAQnumberchars 2 coo ka e a e p oe Ee a 136 4 1 141number_codes 2 137 AA MR Led e A ee eS 138 LEAR ei o ii e e o a 139 LAMAS pido codes E 140 AM AI 141 AA JAG op specitier l colonos ideada 143 41 14 partial ViSt L eea ee a da 144 A LAS peeR Bytes cies tee whe REWER ERE sa 144 4 1 149peek_byte 2 ico wow ewe Eee Eee 145 AL loU peek char 1 1 cee eee we ipapa te dri 146 415i peek char 2 ocd ee ee ee ea ee ee 146 Al 162peek_ code l oss cone semo ed aap e Re 147 AM Ipo peak Codey 2 orie a Ree eR Se 8 a 148 A Toe phrase Za fog ole x Re A eed ini gre 149 AM lOO phrase 3 oo on hk ee ee hae RS 149 AL ASG POLA Zo ach tS ae ee oe a 2 151 AL lo portray_clamee 1 o so e paora ee oe e ee a 151 4 1 158portray_clause 2 152 4 1 159postfix_ op specifier l o sios skiyor e enaa 153 4 1 160 predicate_indicator 1 153 AA 16 Lpredication 1 ion hoe A wR a 154 4 1 162prefix_op_specifier l 154 o o s coe cscs eee wee he wl oe eg ee a 155 AN AGS DEIA og ek A ee he RR ee a OR Be 156 4 1 165print_message 2 156 4 1 166print_message_lines 3
12. VAR 2 Count 3 yes Errors instantiation_error The argument Start was not instantiated type_error integer Start The argument Start was not an integer domain_error not_less_than_zero Start The argument Start must not be less than zero See also write_term 3 writeq 2 134 CHAPTER 4 BUILT IN PREDICATES 4 1 136 nonvar 1 Synopsis nonvar T Description Succeeds if T is not a variable This predicate behaves as if it was defined as follows nonvar T var T Examples nonvar 9 yes nonvar foo X X _523056 yes nonvar X no Errors None See also var l ALIS 1 Synopsis we CAT Description Succeeds if and only if cal1 T fails This is negation by failure This predicate behaves as if it were defined as follows T call T gt fail true 4 1 PREDICATES 135 Examples fail yes true no Errors instantiation_error The argument T was not instantiated type_error callable T The argument T was not a callable term See also None 4 1 138 nth0 3 Synopsis nth0 N L E nthO N L E Description Succeeds if the list L at index N contains the element E The first element has index 0 This predicate is deterministic Examples nthO N a b c c N 2 yes nth0 1 a b c E E b2 yes Errors None See also nth1 3 136 CHAPTER 4 BUILT IN P
13. assert 1 callable_term 1 4 1 194 retractall 1 Synopsis retractall T Description Removes all dynamic clauses from the clause store which have a head term that unifies with the argument T Behaves as if it were defined as follows retractall Head retract Head _ fail true 4 1 PREDICATES Examples assert foo 1 assert foo 2 yes listing foo 1 foo 1 foo 2 yes retractall foo _ yes listing foo 1 yes Errors See retract 1 See also retract 1 4 1 195 reverse 2 Synopsis reverse L1 L2 Description Succeeds if the list L1 is the reverse of L2 Examples reverse A 1 2 3 A 3 2 1 yes reverse A B A B 11 Fa A _29760 B 29760 A _29760 29840 B _29840 _29760 179 180 CHAPTER 4 BUILT IN PREDICATES gt ll _29760 29840 29920 _29920 29840 29760 w ll Errors None See also None 4 1 196 seek 4 Synopsis seek Stream 0ffset Whence Result Description Sets the byte offset of the stream indicated by Stream to a new byte offset determined by Offset and Whence then unifies this new offset with Result Stream can be either a binary or a text stream The byte offset is not necessarily the same as the character or character code offset such as in the case of a Unicode text stream The argument Offset is an integer value greater tha
14. domain_error stream_or_alias S The argument Sis not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error One of the arguments S or C was not instantiated permission_error output stream S There is a lack of permission to write to stream S permission_error output binary_stream S The argument S refers to a binary stream representation_error character_code C The argument C was instan tiated but was not a valid character code type_error integer C The argument C was instantiated but was not an integer See also character_code 1 integer 1 4 1 183 query_class 5 Synopsis query_class Class Prompt InputMethod MapMethod FailureMode Description This predicate is used internally by ask_query 4 The predicate Class names the query class being defined This will correspond to the first argu ment of ask_query 4 The arguments Prompt and InputMethod are used in a subsequent call query_input InputMethod Prompt Input The argument MapMethod is used along with Input from the previous call query_map MapMethod Input Result Answer The predicate ask_query 4 will then use the argument FailureMode to de termine what to do if Result is unified with failure in the previous call The predefined query classes are 170 CHAPTER 4 BUILT IN PREDICATES query_class query T Vs term T variable_names Vs query query_class so
15. file_search_path 2 open 4 4 1 5 add_file_search_path 2 Synopsis add_file_search_path A D Description Creates the mapping between the path alias A and the directory D which is used by file_search_path 2 which is in turn used by absolute_file_name 2 to build file names Examples add_file_search_path logging dir usr local logs yes absolute_file_name logging dir system log A A usr local logs system log yes Errors instantiation_error Fither the argument A or the argument D was not instantiated type_error atom A The argument A was not an atom See also current_file_search_path 2 del_file_search_path 2 4 1 PREDICATES 27 4 1 6 add_generate_message 1 Synopsis add_generate_message A Description Registers the predicate identified by the predicate indicator A 3 as a generate message hook A generate message hook is a predicate with arity 3 the first argument being the input term the second argument being the expansion of the input term the third being unified with the atom when it is called When a message is written by print_message 2 then the second argument is given to each generate message hook one at a time in the order they were registered with add_generate_message 1 If one of the hooks succeeds then the message which was given as an argument is discarded and its expansion is used instead If none of the hooks succeed then the process just contin
16. h yes Errors None 88 CHAPTER 4 BUILT IN PREDICATES See also delete_al1 3 4 1 84 delete_deterministically 3 Synopsis delete_deterministically Element Before After Description Deletes the first occurrence of Element from the list Before giving the list After The members of Before are compared with Element using 2 This predicate is a deterministic version of de1 3 Examples delete_deterministically 1 1 2 1 Lst Lst 2 1 yes delete_deterministically X 1 2 1 Lst X 1 Lst 2 1 yes Errors None See also del 3 4 1 85 Disjunction 2 Synopsis T1 T2 Description This is the disjunction predicate It succeeds if at least one of either T1 or T2 succeed 4 1 PREDICATES Examples fail true yes Errors None See also None 4 1 86 display 1 Synopsis display T Description Behaves as if it were defined as follows display Term current_output S display S Term Examples See display 2 Errors See display 2 See also display 2 4 1 87 display 2 Synopsis display S T 89 90 CHAPTER 4 BUILT IN PREDICATES Description Behaves as if it were defined as follows display Stream Term write_term Stream Term ignore_ops true Examples See write_term 2 Errors See write_term 2 See also write_term 2 4 1 88 Dot 2 Synopsis File Fi
17. yes X is 2 div 3 X 0 7 4 1 PREDICATES yes X is 2 div 3 1 yes X is floor 1 5 12 yes X is gamma 1 5 2 363271 yes X is In exp 1 1 0 yes X is log 10 S107 yes X is 5 mod 3 2 lt 2 yes X is 5 mod 3 1 yes X is 5 3 15 yes X is 5 rem 3 yes X is 5 rem 3 yes X is round 5 3 97 98 CHAPTER 4 BUILT IN PREDICATES yes X is round 5 3 X 5 yes X is 5 Y is X X 5 Y 5 yes X is sin 1 X 0 841471 yes X is sqrt 2 X 1 414214 yes X is 2 3 X 1 yes X is truncate 3 14 X 3 yes Errors domain_error not_less_than_zero An argument that should have been greater than or equal to zero was not evaluation_error zero_divisor An attempt was made to divide by zero instantiation_error A given expression was an uninstantiated variable type_error evaluable E A given expression was not evaluable type_error evaluable F N A given compound did not have an arith metic functor type_error integer N An argument which should have been an integer was not See also floating_point_precision 4 1 PREDICATES 99 4 1 91 Existential quantification gt 2 Synopsis V T Description Succeeds if there exists a V such that T is true This is equivalent to call T Examples X print hello nl hello X
18. 2 5 1 Abort This choice is equivalent to a call of abort 0 This is useful if your code is stuck in an endless loop and you wish to abort the execution and jump back to the query prompt 2 5 2 Continue This choice simply exits the interrupt handler and continues execution from where it was interrupted 8 CHAPTER 2 USING BARRY S PROLOG 2 5 3 Set debug flag This choice is equivalent to a call of debug 0 This is useful if the debugger is loaded and you have spypoints set but debugging is turned off Setting the flag debug will then mean that the next spypoint hit will enter the debugger 2 5 4 Exit Prolog This choice is equivalent to a call of halt 0 2 5 5 Clear trace amp debug flags This choice is equivalent to a call of nodebug 0 2 5 6 Set trace amp debug flags This choice is equivalent to a call of trace 0 This is useful if the debugger is loaded and you wish to see whereabouts in the code you are executing Chapter 3 The Prolog Language 3 1 Syntax Input is written using the Unicode character set The syntax rules which determine if a sequence of input characters is acceptable Prolog are a superset of those defined by the ISO standard By far the most important syntax rule defines the term it is either a variable an atom a number or a compound Variables There are two mutually exclusive types of variable which are distinguished according to the format of their names Anonymous A variable with
19. 4 1 PREDICATES 31 4 1 9 add_portray_message 1 Synopsis add_portray_message A Description Registers the predicate identified by the predicate indicator A 2 as a por tray message hook A portray message hook which is not to be confused with a portray hook is a predicate with arity 2 the first argument being a severity term and the second argument the message to be portrayed Such a hook can be used to override the operation of print_message 2 which will call all registered hooks until one succeeds Should no hook succeed then print_message 2 is written as it normally would be Portray message hooks are found in the order that they are registered with add_portray_message 1 The subsequent registration of an already registered hook has no effect Examples assert ph Severity Message print Hook provided with print Severity Message nl Severity _523024 Message _525456 yes add_portray_message ph Hook provided with informational yes foo a b c d Hook provided with error error existence_error predicate foo 4 existence_error foo a b c d not_applicable predicate foo 4 Errors instantiation_error The argument A was not instantiated type_error atom A The argument A was not an atom See also current_portray_message 1 del_portray_message 1 32 CHAPTER 4 BUILT IN PREDICATES 4 1 10 add_query_class_hook 1 Synopsis add_query_class_hook A Descr
20. AF Description The relative file name RF is translated into the absolute file name AF The argument RF is a term such that source_sink RF is true and AF is an atom whose name is the corresponding absolute file name The argument Options is a list of terms which control the translation process Should conflicting options be given the last such option in the list is given precedence The list of valid option terms are as follows 24 CHAPTER 4 BUILT IN PREDICATES access A The access permission or existence of AF can be checked or even ignored with this option If Options contains file_errors error then an exception will be thrown upon permission or existence errors otherwise the call of absolute_file_name 3 will fail Here A can either be an atom or a list of atoms chosen from the following read The file specified by AF must be readable write The file specified by AF must be writable or at least it can be created if it does not exist append The same as the option write but with the addition that the file position can be set to the end of the file exist The file specified by AF must already exist none The file system is not used nothing is checked and no errors can occur extensions E The argument E is either an atom or a list of atoms Each such atom is a file extension that should be tried when building AF The atom with no name signifies no extension Should RF have an extension already then this op
21. callable_term foo yes callable_term 99 7 no callable_term T no Errors None See also cal1 1 4 1 41 catch 3 Synopsis catch T1 T2 T3 Description Sets up an environment for the duration of a call of T1 whereby any un handled call to throw 0bj where T2 0bj is handled by a call to T3 subject any variable bindings introduced by T2 0bj This means catch 3 can succeed in two ways i cal1 T1 succeeds or ii ca11 T1 throws an unhandled exception with throw 0bj where T2 0bj and T2 0bj cal1 T3 succeeds 58 CHAPTER 4 BUILT IN PREDICATES Should it be the case that T2 0bj fails then the throw is unhandled and any outer catch 3 environments are checked for successful handling Should call T1 or ca11 T3 fail then cal1 3 fails Examples catch true object print cought n1 yes catch fail object print cought n1 no catch throw object object fail no Errors instantiation_error The argument T1 was not instantiated type_error callable T1 The argument T1 was not a callable term See also throw 1 4 1 42 char_code 2 Synopsis char_code Char Code char_code Char Code Description Succeeds if the one atom character Char has the character code Code Examples char_code Char 65 Char A yes char_code B Code Code 66 yes 4 1 PREDICATES 59 Errors instantiation_
22. discard any other possible answers for AF all Make absolute_file_name 3 non deterministic i e a later fail ure could give another answer for AF Examples bagof P absolute_file_name f_b file_type prolog ignore_underscores true solutions all access none P Ps P _521856 Ps f_b fasl f_b pl f_b fb fasl fb pl fb yes absolute_file_name login access none P P home bwat login yes Errors instantiation_error The arguments RF and Options were not both ground domain_error source_sink RF The argument RF is not a source _sink term domain_error absolute_file_name_option 0 An invalid option 0 was glven type_error list 0 The argument Options wasn t a proper list Note it is not necessarily so that O will be the full argument Options permission_error access read AF The access permissions of the file specified by AF didn t include reading 26 CHAPTER 4 BUILT IN PREDICATES permission_error access write AF The access permissions of the file specified by AF didn t include writing permission_error access append AF The access permissions of the file specified by AF didn t include appending existence_error source_sink AF The file specified by AF doesn t exist permission_error access home_directory UserName The home direc tory of the user UserName couldn t be accessed due to a lack of per mission See also
23. gt mouse T assert T T noun _547440 _547408 _547440 mouse _547408 yes expand_term verb gt chases T assert T T verb _547664 _547632 _547664 chases _547632 yes phrase s L L a cat chases a cat yes phrase s the dog chases the cat yes phrase s the cat chases the mouse all day L L all day yes Errors instantiation_error The argument R was not instantiated type_error callable R The argument R was not a callable term 4 1 PREDICATES 151 See also Section 4 2 4 1 156 portray 2 Synopsis portray S T Description Succeeds if there is a portray hook that has been registered with add_portray 1 that succeeds with the same arguments This predicate behaves as if it was defined as follows portray Stream Term current_portray Functor Goal Functor Stream Term call Goal Examples assert my_portray S foo write S goo_not_foo nl S _524784 yes add_portray my_portray yes portray user_output foo goo_not_foo yes Errors None See also add_portray 1 current_portray 1 del_portray 1 4 1 157 portray_clause 1 Synopsis portray_clause C 152 CHAPTER 4 BUILT IN PREDICATES Description This predicate behaves as if it was defined as follows portray_clause C current_output S portray_clause S C
24. instantiation_error The argument A was not instantiated type_error atom A The argument A was not an atom See also current_generate_message 1 del_generate_message 1 expand_term 2 4 1 7 add_message_hook 1 Synopsis add_message_hook A Description Registers the predicate identified by the predicate indicator A 3 as a message hook A message hook is called by the procedure print_message 2 with the first argument being the message severity the second being the message and the third being the list of message lines The first hook that succeeds terminates the message printing process If no such hook succeeds or no hook has been registered then print_message 2 prints the lines onto the stream user_error Examples assert test Severity Msg Lines format Severity w nMsg w nLines wn 4 1 PREDICATES 29 Severity Msg Lines print_message_lines user_error Severity Lines Severity _620352 Msg _622160 Lines _623168 yes add_message_hook test Severity informational Msg yes Lines w Lyes yes Severity query Msg Lines print_message error I am an error Severity error Msg I am an error Lines w I am an error I am an error Severity informational Msg yes Lines w yes yes Severity query Msg Lines Errors instantiation_error The argument A was not instantiated type_error atom
25. sample_median 1 2 3 4 5 6 7 8 9 10 Result Result 5 0 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as all members of the argument L are evaluated errors may be thrown by eval 2 326 CHAPTER 13 THE STATISTICS LIBRARY See also sample_quantile 3 13 1 19 sample_median_absolute_deviation 2 Synopsis sample_median_absolute_deviation L Result Description Result is the arithmetic mean of the absolute deviations of the members of the list of numbers L from the median of L This predicate behaves as if it were defined as sample_mean_absolute_deviation L Result sample_median L Median sample_absolute_deviation L Median Result Examples sample_median_absolute_deviation 1 2 3 R R 0 666667 yes Errors domain_error non_empty_list The argument L was the empty list 0 instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_absolute_deviation 3 13 1 20 sample_quantile 3 Synopsis sample_quantile L Q Result 13 1 PREDICATES 327 Description Result is the 1 Q quantile of the list of numbers L This predicate behaves as if
26. yes 50 CHAPTER 4 BUILT IN PREDICATES Errors instantiation_error At least one of the arguments A or I was not instan tiated type_error integer I The argument I was not an integer domain_error not_less_than_zero I The argument I was less than zero See also None 4 1 31 atom_length 2 Synopsis atom_length T N Description The number of characters in the name of atom T is the integer N Examples atom_length atom_length N N 11 7 yes atom_length N N 0 7 yes Errors instantiation_error The argument T was not instantiated type_error atom T The argument T was not an atom type_error integer N The argument N was instantiated and not an in teger domain_error not_less_than_zero I The argument N was instantiated and was an integer less than zero See also None 4 1 PREDICATES 51 4 1 32 atomic 1 Synopsis atomic T Description Succeeds if the term T is atomic This definition of atomic term is i all atoms are atomic terms and ii all integers are atomic terms Note that floating point numbers are not atomic the reason being that they are represented by compound terms Examples atomic atomic yes atomic 99 yes atomic 99 0 no Errors None See also atom 1 integer 1 4 1 33 between 3 Synopsis between Low High Value Description Succeeds if Low lt Value and Value lt High This p
27. yes Errors None See also None 4 1 206 stream_alias 2 Synopsis stream_alias A 7S Description Succeeds if the atom A is an alias for the stream identified by the stream term S That is to say alias A is a property of S Examples stream_alias user_input S S stream 0 yes Errors None See also None 192 CHAPTER 4 BUILT IN PREDICATES 4 1 207 stream_position_byte_count 2 Synopsis stream_position_byte_count Position Count Description This predicate succeeds if Position is a stream position term and Count is the number of bytes read from or written to the stream Examples See set_stream_position 2 Errors None See also set_stream_position 2 stream_property 2 4 1 208 stream_position_character_count 2 Synopsis stream_position_character_count Position Count Description This predicate succeeds if Position is a stream position term and Count is the number of characters read from or written to the stream Examples See set_stream_position 2 Errors None See also set_stream_position 2 stream_property 2 4 1 PREDICATES 193 4 1 209 stream_position_line_count 2 Synopsis stream_position_line_count Position Count Description This predicate succeeds if Position is a stream position term and Count is the number of lines written to or read from the stream A newly opened stream has a line count of 1 Giving the first line a count
28. 0 0 0 yes Errors None 276 CHAPTER 9 THE ORDSET LIBRARY See also ord_all_subsets 2 9 1 5 ord_all_unordered_pairs 3 Synopsis ord_all_unordered_pairs 01 02 703 Description Succeeds if the ordered set 03 contains all unordered pairs of the ordered sets 01 and 02 Each pair is itself an ordered set which means that the order of the first two arguments does not matter Examples ord_all_unordered_pairs 1 2 3 a b R R 1 a1 1 b 2 a 2 b 3 a 3 bJ yes ord_all_unordered_pairs a b 1 2 3 R R 1 a1 1 b 2 a1 2 b 3 a 3 bJ yes Errors None See also ord_product 3 9 1 6 ord_disjoint 2 Synopsis ord_disjoint 01 02 Description Succeeds if the two ordered sets 01 and 02 have no element in common 9 1 PREDICATES 277 Examples ord_disjoint 1 2 3 4 5 6 yes ord_disjoint 1 2 3 3 4 5 no Errors None See also None 9 1 7 ord_insert 3 Synopsis ord_insert 01 E 02 Description Succeeds if the ordered set 02 is equal to the ordered set 01 with the element E inserted into it Examples ord_insert 1 2 3 4 0 0 1 2 3 4 yes ord_insert 1 2 3 2 1 2 3 yes Errors None See also None 9 1 8 ord_intersect 2 Synopsis ord_intersect 01 02 278 CHAPTER 9 THE ORDSET LIBRARY Description Succeeds if the ordered sets 01 and 02
29. 12 1 11 is_lower 1 Synopsis is_lower Code Description Succeeds if Code represents an English language letter of lower case 12 1 PREDICATES Examples is_lower 0 c yes is_lower 0 C no Errors As Code is evaluated errors may be thrown by eval 2 See also None 12 1 12 is_newline 1 Synopsis is_newline Code Description Succeeds if Code is the newline code ASCII 10 Examples is_newline X X 10 yes Errors None See also None 12 1 13 is_paren 2 Synopsis is_punct LeftCode RightCode 301 302 CHAPTER 12 THE READSENT LIBRARY Description Succeeds if the pair LeftCode RightCode represents one of the following pairs characters or 4 Examples is_paren 0 0 yes Errors None See also None 12 1 14 is_period 1 Synopsis is_period Code Description Succeeds if Code represents one of the following characters or Examples is_period 0 yes Errors None See also None 12 1 15 is_punct 1 Synopsis is_punct Code 12 1 PREDICATES Description Succeeds if Code represents one of the following characters Examples is_punct 0 yes Errors None See also None 12 1 16 is_upper 1 Synopsis is_upper Code Description zap OT s Succeeds if Code represents an English language letter of upper case Examples
30. A fgh yes atom_codes yes Errors instantiation_error Either both arguments were uninstantiated or A was uninstantiated and L was not ground type_error atom A The argument A was instantiated but it was not an atom type_error list L The argument L was instantiated but it was not a list representation_error character_code The argument L contained an el ement which was not a character code domain_error code_list_not_too_long L The argument L contained too many elements See also atom_chars 2 character_code 1 name 2 4 1 29 atom_concat 3 Synopsis atom_concat T1 T2 T3 atom_concat T1 T2 T3 Description The name of atom T3 is a concatenation of the names of the atoms T1 and T2 in that order 4 1 PREDICATES 49 Examples atom_concat hello world A A helloworld yes atom_concat A world helloworld A hello yes Errors instantiation_error Either both T1 and T3 are uninstantiated or both T2 and T3 are uninstantiated type_error atom T An instantiated argument T was not a concatable atom See also concatable_atom 1 4 1 30 atom_index 3 Synopsis atom_index A 1 C Description Succeeds if the It character code of the name of the atom A is C The first character code is indexed by the integer 0 Examples yes atom_index foo 1 C C 111 yes atom_index foo 0 C C 102
31. Conditionals The grammar operator gt 2 behaves in the same way as the Prolog pred icate with the same name but it must be the topmost grammar operator on the left hand side of a 2 you can t have a gt 2 without a 2 The grammar rule for the conditional forces gt 2 to be non associative dcg_body_conditional gt dcg_body_conjunction gt dcg_body_conjunction Conjunctions As in a Prolog clause 2 denotes conjunction which is equivalent to a grammatical concatenation The second conjunction rule shows that this is optional dcg_body_conjunction gt dcg_body_not 7 dcg_body_conjunction dcg_body_conjunction gt dcg_body_not 4 2 DEFINITE CLAUSE GRAMMAR 223 Negations The optional grammar operator 1 behaves as its namesake does in Prolog dcg_body_not gt dcg_body_not dcg_body_not gt dcg_body_terminal It is translated verbatim expand_term a gt b T T a _553552 _ 553520 A b _553552 554784 _553552 _553520 yes Terminals Note we re confusing the term terminals which usually means symbols from some alphabet with atomic DCG terms We ll call the symbols actual terminals The terminals are perhaps unsurprisingly described by the largest gram matical category A terminal can be a single variable the operator 1 is described later dcg_body_terminal
32. Description Behaves as if it were defined as follows phrase R L phrase R L Examples See phrase 3 Errors See phrase 3 See also phrase 3 4 1 155 phrase 3 Synopsis phrase R L0 L1 Description Succeeds if there is a list L2 such that append L2 L1 LO and L2 belongs to the language of definite clause grammar rule R To put it another way some prefix of the list LO can be generated accepted by the definite clause grammar rule R and what follows after this prefix is the list L1 Examples expand_term s gt np vp T assert T T s _546656 546624 np _546656 _547920 vp _547920 546624 yes expand_term np gt det noun T assert T T np _547552 547520 det _547552 548816 noun _548816 _547520 yes 150 CHAPTER 4 BUILT IN PREDICATES expand_term vp gt verb np T assert T T vp _547328 _ 547296 verb _547328 _ 548592 np _548592 547296 yes expand_term det gt a T assert T T det _546320 _546288 _546320 al_546288 yes expand_term det gt the T assert T T det _546768 546736 _546768 the _546736 yes expand_term noun gt cat T assert T T noun _546992 _546960 _546992 cat _546960 yes expand_term noun gt dogl T assert T T noun _546992 _546960 _546992 dog _546960 yes expand_term noun
33. Description Succeeds if the term T1 can be constructed from the elements of the list T2 where the head of T2 is the principle functor of T1 and the remaining elements of T2 are the arguments of T1 in the correct order This predicate considers atomic terms to be compounds of arity zero Floating point numbers are processed as the compound terms that represent them Examples foo 1 2 3 L L f00 1 2 3 yes T a b T a b yes 99 L L 99 yes foo L L foo yes 3 14 L L float 14480694097861998019 2 64 yes Errors domain_error non_empty_list The argument T2 was the atom instantiation_error Either both T1 and T2 are not instantiated or both T1 and the head of the list T2 are not instantiated representation_error max_arity The length of the list L2 was too long 210 CHAPTER 4 BUILT IN PREDICATES type_error atom H The head of the list T2 is H which is not an atom and T2 contains more than one element type_error atomic H The argument T2 is a single element list H and H is not atomic type_error list L The argument T2 was not a proper list The prob lematic sub list is L See also functor 3 4 1 231 var 1 Synopsis var T Description Succeeds if T is an uninstantiated variable Examples var 99 no var X X _524480 yes X 99 var X no Errors None S
34. Each entry corresponds to a non terminal and an input sequence Goal caching is controlled by these two options cache_goals off Do not cache parse results cache_goals on Cache parse results The lack of such an option is equivalent to passing cache_goals off 6 1 PREDICATES 241 6 1 Predicates 6 1 1 bup_compile 2 Synopsis bup_compile FileInput FileQutput Description Behaves as if it were defined as bup_compile FileInput File0utput bup_compile FileInput File0utput Examples See bup_compile 3 Errors See bup_compile 3 See also bup_compile 3 6 1 2 bup_compile 3 Synopsis bup_compile FileInput FileOutput Options Description A BUP grammar is read in from FileInput The parser source code which is generated in accordance with Options is written to File0utput The argument Options is a list of terms Each element of this list must be one of the following dictionary_lookup Functor off Terminals not found in the parser s grammar are searched for by calling the predicate Functor 4 dictionary_lookup Functor on Terminals not found in the parser s gram mar are searched for by calling the predicate Functor 4 All terminals successfully found are cached in the clause store using the predicate bup_wf_dict 4 cache_goals off No goals are cached 242 CHAPTER 6 THE BUP LIBRARY cache_goals on Successful goals are cached in the clause store using the predicate b
35. Examples current_portray F no add_portray foo yes current_portray F F foo yes del_portray foo yes current_portray F no Errors None 74 CHAPTER 4 BUILT IN PREDICATES See also add_portray 1 del_portray 1 4 1 64 current_portray_message 1 Synopsis current_portray_message F Description Succeeds if at some point add_portray_message F has been called to add the procedure specified by the predicate indicator F 2 Examples current_portray_message F no add _portray_message foo yes current_portray_message F F foo yes del _portray_message foo yes current_portray_message foo no Errors None See also add_portray_message 1 del_portray_message 1 4 1 65 current_predicate 1 Synopsis current_predicate T Description Succeeds if T is a predicate indicator which identifies a dynamic predicate This means that no compiled predicates can be found by T 4 1 PREDICATES 79 Examples assert foo h yes current_predicate foo N N 07 yes Errors type_error predicate_indicator T The argument T was neither unin stantiated nor a predicate indicator See also predicate_indicator 1 4 1 66 current_prolog_flag 2 Synopsis current_prolog_flag F V Description Succeeds if the Prolog flag F currently has the value V Examples current_pro
36. See also None 8 1 3 last 2 Synopsis last E L Description Succeeds if E is the last element of the list L 8 1 PREDICATES 257 Examples last E 1 2 3 E 37 yes last E no Errors None See also None 8 1 4 nextto 3 Synopsis nextto E1 E2 L Description Succeeds if the list L contains the elements E1 and E2 and that these two elements are positioned next to each other Examples nextto A B 1 2 3 A 1 B 2 7 Errors None See also None 258 CHAPTER 8 THE LISTS LIBRARY 8 1 5 nmember 3 Synopsis nmember E L N Description Succeeds if the list L contains the element E at index N Examples nmember E a b c N E a N 1 E b no Errors None See also None 8 1 6 nmembers 3 Synopsis nmembers Ns L Es Description Succeeds if the list L contains the elements of the list Es at the corresponding indices of the list Ns Examples nmembers 2 a b c L L b 8 1 PREDICATES 259 yes nmembers 3 2 1 a b c L L c b a yes Errors None See also None 8 1 7 nth1 3 Synopsis nthi N L E nthi N L E Description Succeeds if the list L at index N contains the element E The first element has index 1 This predicate is deterministic Examples nthi N a b c c N 3 7 yes nthi 2 a b c E E b yes
37. _520432 yes Errors None See also calls 4 1 92 expand_term 2 Synopsis expand_term T E Description Expands the the term T using term expansion hooks and Definite Clause Grammar DCG translations giving the result E First term_expansion 2 is called and the result of this is passed on to the internal DCG expander Examples expand_term a gt b E E a _541648 541616 b _541648 541616 yes Errors None 100 CHAPTER 4 BUILT IN PREDICATES See also Section 4 2 term_expansion 2 4 1 93 fail 0 Synopsis fail Description The predicate which never succeeds Examples fail h no Errors None See also true 0 4 1 94 file_search_path 2 Synopsis file_search_path A D Description Translates a path alias A into a directory D The connection between an alias and a term is made with add_file_search_path 2 If this term is an atom then this is also the directory result of file_search_path 2 If however this term is a compound with a single argument then we treat the functor as another alias to be resolved and the argument as the directory name to be appended onto the result of resolving the new alias It is the result of the append that becomes the result of add_file_search_path 2 4 1 PREDICATES 101 Examples add_file_search_path logging dir usr local logs yes file_search_path logging dir D D usr local logs
38. assert C Description Equivalent to assertz C 4 1 PREDICATES 43 Examples See assertz 1 Errors None See also asserta 1 4 1 22 asserta 1 Synopsis asserta C Description Adds the clause C to the clause store The first clause of the relevant proce dure will be C To ensure that all clauses have a body term if C is an atom or a compound term with a principle functor different from 2 then the argument is rewritten to be C true Examples asserta foo 2 yes asserta foo 1 yes foo X print X nl fail print done nl 1 2 done X _521408 yes Errors instantiation_error The head of the argument C was not instantiated type_error callable Head The head of the argument C was not callable that is to say it was not a predication type_error callable Body The body of the argument C was not callable that is to say not a well formed body term 44 CHAPTER 4 BUILT IN PREDICATES permission_error modify static_procedure Proc The procedure to be modified was static See also assert 1 assertz 1 predication 1 well_formed_body_term 1 4 1 23 assertz 1 Synopsis assertz C Description Adds the clause C to the clause store The last clause of the relevant proce dure will be C To ensure that all clauses have a body term if C is an atom or a compound term with a principle functor different from 2 then the argument is r
39. c d e T T a _556800 _556768 b _556800 _558064 c _558064 559440 d _558064 _559440 e _559440 _556768 yes A rule a is referenced by another rule b when the non terminal on the left hand side of a is used in the right hand side of b dcg_body_terminal gt dcg_nonterminal A non terminal on the right hand side is expanded into the appropriate call expand_term a gt a T T a _542064 _542032 a _542064 _542032 yes 226 CHAPTER 4 BUILT IN PREDICATES Terminal Lists As shown above actual terminals are provided in a list dcg_terminals gt Term dcg_terminals gt Term dcg_terminals The following two rules are equivalent rule_a gt one two three rule_b gt one two three Non terminals As we can see from its grammar rule a non terminal is a callable term dcg_nonterminal gt Term callable_term Term This callable term is the basis of the procedure name for this rule Each term has two arguments added to it and these are equivalent to the two list arguments that our hand crafted Prolog clauses had in the examples given earlier expand_term a gt b T T a _542064 542032 b _542064 542032 yes expand_term a 1 2 gt b T T a 1 2 _545408 _545376 b _545408 _545376 yes 4 3 Flags 4 3 1 bounded Description This flag is specified by both the ISO Prolog an
40. character T Description Succeeds if T is a character Examples character 99 no character character c yes Errors None See also None 4 1 45 character_code 1 Synopsis character_code T Description Succeeds if T is a character code 4 1 PREDICATES 61 Examples character_code 99 yes character_code no character_code c no Errors None See also None 4 1 46 clause 2 Synopsis clause H B Description Succeeds if the term H B has been asserted into the clause store Only dy namic a k a public predicates are found in the clause store Predicates which are static a k a private cannot be retrieved with clause 2 Examples assert foo yes clause foo true yes Errors instantiation_error The argument H was not instantiated type_error callable H The argument H was not a callable term type_error callable B The argument B was neither a variable nor a callable term permission_error access private_procedure F N The argument H was the head term of a private procedure which has the predicate indicator F N 62 CHAPTER 4 BUILT IN PREDICATES See also callable_term 1 4 1 47 close 1 Synopsis close S Description Equivalent to close S See close 2 Examples See close 2 Errors See close 2 See also close 2 4 1 48 close 2 Synopsis
41. close S 0 Description Closes the stream S according to the list of options 0 The possible members of the options list are e force false If there is an error upon closing then the stream is not closed e force true The stream is always closed regardless of whether closing is in error or not If there is an error upon closing the stream contents may be in an invalid state The default option in the case 0 is force false In the event that 0 contains conflicting options the last such option takes precedence 4 1 PREDICATES 63 Examples open foo txt write Stream0 close Streamo0 Stream0 stream 3 yes Errors instantiation_error The argument S was not instantiated or the argu ment and O was not ground existence_error stream S The argument S was not an open stream domain_error stream_or_alias S The argument S was neither an atom nor a stream term type_error list 0 The argument O was not a list domain_error close_option Option The argument O was a list which contained an invalid option Option See also close 1 4 1 49 compare 3 Synopsis compare A L R Description Succeeds if the relation A holds between the terms L and R This predicate behaves as if it were defined as follows compare lt A B A lt B compare gt A B A B B compare A B A Examples compare 2 2 yes compare lt
42. current_portray_message 1 84 CHAPTER 4 BUILT IN PREDICATES 4 1 78 del_query_class_hook 1 Synopsis del_query_class_hook A Description Deregisters a query class hook registered with add_query_class_hook 1 This predicate always succeeds Examples current_query_class_hook F no add_query_class_hook foo yes current_query_class_hook F F foo yes del_query_class_hook foo yes current_query_class_hook F no Errors None See also add_query_class_hook 1 current_query_class_hook 1 4 1 79 del_query_input_hook 1 Synopsis del_query_input_hook A Description Deregisters a query input hook registered with add_query_input_hook 1 This predicate always succeeds 4 1 PREDICATES 85 Examples current_query_input_hook F no add_query_input_hook foo yes current_query_input_hook F F foo yes del_query_input_hook foo yes current_query_input_hook F no Errors None See also add_query_input_hook 1 current_query_input_hook 1 4 1 80 del_query_map_hook 1 Synopsis del_query_map_hook A Description Deregisters a query map hook registered with add_query_map_hook 1 This predicate always succeeds Examples current_query_map_hook F no add_query_map_hook foo yes current_query_map_hook F F foo yes del_query_map_hook foo yes 86 CHAPTER
43. fail true yes 1 fail true 7 no 1 fail gt fail true yes once fail true yes Errors None See also None 4 1 72 del 3 Synopsis del Element Before After Description Succeeds if deleting Element from the list Before is equal to the list After Examples del A 1 2 3 L A 1 L 2 3 A 2 L 1 3 80 CHAPTER 4 BUILT IN PREDICATES E 1 2 h no Errors None See also None 4 1 73 del_file_search_path 2 Synopsis del_file_search_path A D Description Deletes any link between the path alias A with the directory D created by add_file_search_path A D This predicate always succeeds Examples add_file_search_path a b yes current_file_search_path a b yes del_file_search_path a b yes current_file_search_path a b no Errors None See also add_file_search_path 2 current_file_search_path 2 4 1 PREDICATES 81 4 1 74 del_generate_message 1 Synopsis del_generate_message A Description Deregisters a generate message hook registered with add_generate_message 1 This predicate always succeeds Examples current_generate_message F no add_generate_message foo yes current_generate_message F F foo yes del_generate_message foo yes current_generate_message F no Errors None S
44. t exit and this is due to clause c C failing A small change to trace2 1 would allow us to trace such an event Another interesting event linked to failure is the recalling of a goal due to the failure of subsequent goals In the running 14 2 THE DEBUGGER 341 example the sub goal b is called twice the second calling being forced by the failure of goal c This recalling will lead to failure as clause b C succeeds only once Again a small change to trace2 1 would allow us to trace recalling events Let us call the failure of the current goal fail and the recalling of a goal due to backtracking redo We change trace2 1 to give us trace3 1 which will trace the events call exit redo and fail trace3 true trace3 G1 G2 trace3 G1 trace3 G2 trace3 G1 G2 trace3 G1 trace3 G2 trace3 G pre G clause G C trace3 C post G pre G write call tab 1 write G nl pre G write fail tab 1 write G nl fail post G write exit tab 1 write G nl post G write redo tab 1 write G nl fail When we feed the goal a to trace3 1 we get the following output trace3 a call call exit call fail redo fail call exit p QT OOoOou0Npy exit yes Here we can easily see how c fails which backtracks to b which in turn fails 14 2 The Debugger The provided debugger is essentially trace 3 extended with the following features e When a goal exits
45. versity of Edinburgh 1981 339 Lawrence Byrd Understanding control flow of prolog programs In Proc Workshop on Logic Programming 1980 339 Pierre Deransart and Jan Maluszynski A grammatical view of logic programming MIT Press 1993 217 MTH 83 Yuji Matsumoto Hozumi Tanaka Hideki Hirakawa Hideo O K90 Miyoshi and Hideki Yasukawa Bup A bottom up parser em bedded in prolog New Generation Comput 1 2 145 158 1983 237 Richard A O Keefe The craft of Prolog Logic programming Cambridge Mass MIT Press 1990 224 361 Index arity 13 atom 10 0 13 fx 15 fy 15 xfx 15 xfy 15 xf Lo yfx 15 yf 15 comment 14 compound term 13 directive 5 discontiguous 1 5 dynamic 1 5 ensure_loaded 1 6 include 1 6 initialization 1 6 multifile 1 6 modulo 230 number_output_base 231 singleton_var_warnings 231 trace 8 355 unknown 231 floating point 11 functor 13 grammatical operator 2172 0 225 3 2 123 gt gt 2 222 gt gt 2 221 2 gt 2 237 232 2 222 1 223 7 1 224 gt 1 gt 2 222 cal1 1 224 phrase 1 223 integer 11 error 5 17 escape code 10 list 13 exception 17 loading 5 execution aborting 7 message 5 exiting 8 interrupting 7 number 11 tracing 8 operator 15 flag 2x gt 2 18 bounded 226 xx gt 2 18 char_conversion 227 2 gt 2 18 char_escapes 10 227 24272 18 collapse_multiple_minuses 227 gt 9 1 18 debug_wri
46. 1 153 predication 1 154 prefix_op_specifier 1 154 print 1 155 print 2 156 print_message 2 156 print_message_lines 3 157 print_tree 1 285 print_tree 2 286 private_procedure 1 158 procedure_property 2 159 prolog_lexical_digit 1 159 prolog_lexical_letter 1 160 prolog_lexical_lower_case_letter 1 10 161 prolog_lexical_symbol 1 10 161 prolog_lexical_upper_case_letter 1 9 162 prolog_lexical_ws 1 14 163 prompt 1 163 public_procedure 1 164 put_assoc 4 236 put_byte 1 165 put_byte 2 165 put_char 1 166 put_char 2 167 put_code 1 168 put_code 2 168 query_class 5 169 query_input 3 170 query_map 4 171 query_read_line 2 172 read 1 172 read 2 173 read_in 1 289 read_in 2 290 read_line 1 303 read_line 2 304 read_sent 1 305 read_sent 2 305 read_sentence 1 306 read_sentence 2 307 read_term 2 173 read_term 3 174 read_until 2 307 read_until 3 308 reconsult 1 176 remove_dups 2 263 remove_spypoint 1 352 repeat 0 177 retract 1 177 retractall 1 178 rev 2 264 reverse 2 179 s_member 3 250 s_to_p_graph 2 250 s_to_p_trans 2 251 s_transpose 2 252 same_length 2 264 sample_absolute_deviation 3 319 sample_arithmetic_mean 2 320 sample_coefficient_of_variation 2 321 sample_geometric_mean 2 322 sample_harmonic_mean 2 323 sample_interquartile_range 2 323 sample_mean_absolute_deviation 2 324 sample_median 2 325 sample_median_absolute_deviati
47. 11 warshal1 2 Synopsis warshall G1 G2 Description This predicate takes a graph G1 in S representation and unifies G2 with a graph in S representation which is the transitive closure of G1 254 CHAPTER 7 THE GRAPHS LIBRARY Examples p_to_s_graph a b b c c d a c S warshall S Closure s_to_p_graph Closure ClosureP s a b c b c c d d Closure a b c d b c d c d d ClosureP a b a c a d b c b d c d yes Errors None See also None Chapter 8 The lists library To use the predicates in this library you will need to load the lists fas file One way to do this is with the following call ensure_1oaded runtime lists 8 1 Predicates 8 1 1 correspond 4 Synopsis correspond E1 L1 L2 E2 Description Succeeds if the position of element El in list L1 corresponds to the position of element E2 in list L2 This predicate is deterministic Examples correspond 1 1 21 a b E E a yes correspond E 1 2 a b b E 2 7 yes Errors None 259 256 CHAPTER 8 See also None 8 1 2 delete 3 Synopsis delete L1 E L2 Description THE LISTS LIBRARY Succeeds is the list L2 is the result of deleting all occurrences of E from the list L1 This predicate is deterministic Examples delete 1 1 1 1 L L 2 yes delete 1 2 3 4 L L 1 2 3 yes Errors None
48. 3 Synopsis op P S A Description Creates or updates the entry in the operator table for the atom s A with operator specifier S and priority P The operator table is used when parsing and printing terms The argument A is either an atom or a list of atoms When it is a list the table entries are created updated for each atom in the list Any such atom is the name of the operator being processed The argument S is an atom and it specifies the fixity and associativity of the operator It must be one of the following fx The operator is prefix and non associative fy The operator is prefix and right associative xfx The operator is infix and non associative xfy The operator is infix and right associative yfx The operator is infix and left associative xf The operator is postfix and non associative yf The operator is postfix and left associative The argument P is an integer and it specifies the priority of the operator The range of this argument is between 0 and 1200 inclusive The lower of two priorities has a higher precedence that is to say it binds more tightly It is not possible to call op 3 to alter the status of the operator A call of op 3 where the priority P is 0 will remove the entry associated with atom A and specifier S There can be no two operators with the same specifier and name There can be no two operators with the same name where one has a prefix specifier and the other has a postfix specifier 1
49. 700 xfy f enabling us to write 1g2f3h By changing the fixity of the operators we have completely transformed the input but it still represents the same term To demonstrate how priority alters the parsing of input consider the input 1f2h which with the definitions given above represents the term 1 h 2 Now should we alter the priority of h 1 from a level lower than 2 to a level higher than it e g op 0 xf h op 800 xf h the term which the input represents changes to h f 1 2 As we can see the operator with the highest priority value becomes the principle functor It is useful to know that parenthesis overrides priorities by giving the term enclosed a priority of zero So we can write 1 f 2 h 3 2 EXCEPTIONS 17 to force 2 to be the principle functor i e give us 1 h 2 Note that the comma that is used to separate functor arguments or list elements is actually an operator 2 with priority 1000 and associativity xfy This means that any term with a principle functor of 1000 or more in an argument or list will have to be written with parenthesis All that remains is to show how associativity alters the parsing of input With the configuration of the operator f 2 as infix right associative xfy the input 11213 would represent the term f 1 2 3 Should we change f 2 to be left associative instead op 0 xfy f op 700 yfx f then the same input
50. DCG grammar rules is very similar to the hand crafted examples Compare the code for noun phrases that we wrote by hand with that generated by expand_term 2 listing noun_phrase 2 dcg_noun_phrase 2 noun_phrase A B det A C noun C B dcg_noun_phrase A B dcg_det A C dcg_noun C B yes 4 2 2 DCG Grammar This section describes the syntax of a DCG rule in terms of DCG rules The consequence of this is that if you want to understand the DCG formalism from this description you will have to either 220 CHAPTER 4 BUILT IN PREDICATES e already understand the DCG formalism or e translate the following grammar into another formalism e g Backus Naur Form by replacing gt with and X with X The grammar of the DCG rule is as follows dcg_rule gt dcg_nonterminal L dcg_terminals gt dcg_body dcg_rule gt dcg_nonterminal gt dcg_body dcg_body gt dcg_body_disjunction dcg_body_disjunction gt dcg_body_conditional dcg_body dcg_body_disjunction gt dcg_body_conditional dcg_body dcg_body_disjunction gt dcg_body_conjunction dcg_body dcg_body_disjunction gt dcg_body_conjunction dcg_body dcg_body_disjunction gt dcg_body_conjunction dcg_body_conditional gt dcg_body_conjunction gt dcg_body_conjunction dcg_body_conjunction gt dcg_body_not dcg_b
51. Offset was not an integer See also open 4 set_stream_position 2 4 1 197 set_input 1 Synopsis set_input T Description Instructs the system to use the stream identified by the argument T as the default input stream 182 CHAPTER 4 BUILT IN PREDICATES Examples current_input S S stream 0 yes open foo txt read InStream set_input InStream current_input InStream close InStream InStream stream 3 yes current_input S S stream 0 yes Errors domain_error stream_or_alias T The argument T was not a valid stream term or alias atom existence_error stream T The argument T identified a nonexistent stream instantiation_error The argument T was not instantiated permission_error input stream T There was no permission to use the argument T as an input stream See also None 4 1 198 set_output 1 Synopsis set_output T Description Instructs the system to use the stream identified by the argument T as the default output stream 4 1 PREDICATES 183 Examples current_output S S stream 1 yes open foo txt write OutStream set_output OutStream current_output OutStream close OutStream DutStream stream 3 yes current_output S S stream 1 yes Errors domain_error stream_or_alias T The argument T was not a valid stream term or alias atom existence_erro
52. PREDICATES representation_error max_arity PI must be a predicate indicator with an arity that is less than the value of the Prolog flag max_arity domain_error not_less_than_zero Arity PI must be a predicate indi cator with an arity that is not less than zero type_error integer Arity PI must be a predicate indicator with an arity that is of type integer type_error atom Name PI must be a predicate indicator with a valid name that is an atom permission_error modify static_procedure PI The predicate to be abolished must not be static See also retract 1 retractall 1 4 1 2 abort 0 Synopsis abort Description Exit the current break level The initial break level cannot be exited This predicate neither succeeds nor fails Examples break Entering break level 1 1 abort yes abort Errors None See also break 0 4 1 PREDICATES 23 4 1 3 absolute_file_name 2 Synopsis absolute_file_name RF AF Description Behaves as if it were defined as follows absolute_file_name RF AF absolute_file_name RF file_type prolog access exist ignore_underscores true file_errors fail AF 1 absolute_file_name RF AF absolute_file_name RF AF Examples See absolute_file_name 3 Errors See absolute_file_name 3 See also absolute_file_name 3 4 1 4 absolute_file_name 3 Synopsis absolute_file_name RF Options
53. PREDICATES setof Template Goal Set bagof Template Goal Bag sort Bag Set Examples bagof X member X 3 2 1 1 2 3 Result X _524928 Result 3 2 1 1 2 3 yes setof X member X 3 2 1 1 2 3 Result X _524928 Result 1 2 3 yes Errors instantiation_error The argument Goal was uninstantiated type_error callable Goal The argument Goal was not callable 187 type_error list Set The argument Set was neither a list nor a partial list See also bagof 3 findal1 3 sort 2 4 1 202 sort 2 Synopsis sort T1 T2 Description Succeeds if T2 is a list representation of the sorted contents of the list T1 where duplicate elements have been removed The ordering relation used is EA Examples sort 3 2 1 1 2 3 L L 1 2 3 188 CHAPTER 4 BUILT IN PREDICATES yes Errors instantiation_error The argument T1 was not instantiated type_error list T1 The argument T1 was not a list See also None 4 1 203 source_sink 1 Synopsis source_sink T Description Succeeds if the given argument is a term which can be used to specify a source or a sink This predicate behaves as if it was defined as follows source_sink Source_sink atom Source_sink gt true compound Source_sink Source_sink _ Arg source_sink Arg Examples source_sink file yes source_sink runtime file yes Er
54. See also reverse 2 8 1 15 same_length 2 Synopsis same_length L1 L2 Description Succeeds if the lists L1 and L2 have the same length 8 1 PREDICATES 265 Examples same_length a b c L L _554624 554672 554720 yes same_length 1 2 3 a b c yes Errors None See also None 8 1 16 select 4 Synopsis select E1 L1 E2 L2 Description Succeeds if the lists L1 and L2 have the same length and differ only in a certain list position where L1 has the element E1 and L2 has E2 Examples select 1 1 1 1 b X X b 1 1 p lt Il 1 b 1 Ps Il 1 1 b 7 no Errors None See also selectchk 4 266 CHAPTER 8 THE LISTS LIBRARY 8 1 17 selectchk 4 Synopsis selectchk E1 L1 E2 L2 Description This is a deterministic version of select 4 This predicate behaves as if it were defined as follows selectchk E1 Li E2 L2 once select E1 Li E2 L2 Examples selectchk 1 1 1 1 b X X b 1 1 no Errors None See also select 4 8 1 18 select 3 Synopsis select E1 L1 L2 Description This predicate behaves as if it were defined as follows select E1 L1 L2 del E1 Li L2 8 1 PREDICATES 267 Examples select E 1 2 3 L E 1 L 2 3 7 E 2 L 1 3 E 3 L 1 2 7 no Errors None See also del 3 selectchk 3 8
55. a foo 1 yes compare R 9 99 64 CHAPTER 4 BUILT IN PREDICATES R lt yes Errors None See also 20 lt gt 2 0 gt 2 gt 2 4 1 50 compound 1 Synopsis compound T Description Succeeds if T is a compound term Note that floating point numbers have a compound representation Examples compound compound Compound Compound _524624 yes compound compound no compound 3 14 yes Errors None See also None 4 1 51 concatable_atom 1 Synopsis concatable_atom T 4 1 PREDICATES Description Succeeds if T is a concatable atom This definition of concatable atom is i all atoms are concatable atoms and ii all variables are concatable atoms Examples concatable_atom foo h yes concatable_atom Foo Foo _524064 yes concatable_atom 99 no Errors None See also atom 1 atom_concat 3 var 1 4 1 52 Conjunction 2 Synopsis T1 T2 Description This is the conjunction predicate It succeeds if both T1 and T2 succeed Examples true true yes Errors None See also None 66 CHAPTER 4 BUILT IN PREDICATES 4 1 53 consult 1 Synopsis consult F Description Opens the file specified by F and loads the terms found in the file into the clause store Note that since consult uses open 4 the argument F is in turn passed to absolute_file_name 2 for tra
56. aa a a Bae 210 4 1 232well_formed_body_term 1 210 ANOS WELT Vs e wo ee ee i ee See e 211 AN ISA oe oh ee ee eo ee 212 AA QS WEA CeO A kh ee ee Ee BA Roe S 212 ALBUL A 2 ase Pee bee eee He ee eS 213 4 123 7write_canonical l o EEE EES 213 AN UBS write canonical vis cua A 214 1 1 239 Write Term 2 occi foe a eo ear Re a 214 AA O40 rite EOS 2c se ee le ba we ee bee ek 215 AAA version 0 6 8 a hee AA Bae a 217 Definite Clause Grammar 00 0004 217 Al MIGEIVERION o irc BS a RES 218 4 22 DUG Morante o os eh Pek ep ee oS 219 4 23 DCG Expansion e c s s 64652 bea eae 221 Plage nb hb ba eae bee eh bw A ae ee 226 Adsl BAET 6 soa ade ea whee Bee 226 Hes CHAT CONVERSION ic e ido ae Ye p bok aes 227 43 3 CHar2SSCapen cp eee ew ea ee 227 4 3 4 collapse_multiple_minuses 227 4 3 5 discontiguous_clauses_warnings 228 4 3 6 duble Quotes e o cere read eR eS 228 4 3 7 floating_point_output_format 229 4 3 8 floating_point_output_precision 229 43 0 floating point precision o a lt e rex wessa 229 4 3 10 integer rounding_function 230 All MALATI ai a aa BO Rete 230 denl MOQU O o y aca sua par o te wl be aAa 230 4 3 13 mumber_output_base 231 4 3 14 singleton_var_warnings gt o o c ers ainka 231 ALO WB RMOWE ee ce Sw a A OG Boe A aw 231 5 The 5 6 The 6 1 7 The tl 8 The 8 1 CONTENTS assoc library 233 a sc i ce e
57. an arithmetic functor will first have all of its arguments evaluated before the functor is interpreted and the result calculated The precision of a number is the amount of bits used in its representation The integers are of arbitrary precision which means that if you multiply two integers then the result may be an integer of greater precision The largest number which can be represented depends upon how much memory can be allocated by the system Floating point numbers are represented by a compound of three arguments parts float F E P F The fraction part This is an integer of fixed precision 92 CHAPTER 4 BUILT IN PREDICATES E The exponent part This is an integer of arbitrary precision P The floating point precision part This determines the number of bits used in the part E above This value is a system wide parameter that can be changed via the flag floating_point_precision Now if F is an integer of P bits then we can imagine that it has the bi nary point at its far right hand side Should we shift the binary point left P E bits then we would have the floating point number represented by float F E P Should P E be less than zero then we would shift the point right by abs P E bits Here is an example current_prolog_flag floating_point_precision P P 64 yes write_canonical 3 14 nl gt float 14480694097861998019 2 64 yes X is 14480694097861998019 gt gt 6
58. as follows listing P current_output S listing S P Examples See listing 2 Errors See listing 2 See also current_output 1 listing 2 4 1 126 listing 2 Synopsis listing Stream Pred Description Displays the clauses connected with the predicate s Pred on Stream The argument Pred can be e A variable which is ignored e A predicate indicator F N If F N specifies an existing dynamic predi cate then the clauses connected with this predicated are passed on to portray_clause 2 If no such dynamic predicate exists then nothing is done and the call succeeds e Anatom A A which is equivalent to a call of listing Stream A O e A list which has its elements processed one at a time 126 CHAPTER 4 BUILT IN PREDICATES Examples assert a b c yes assert d X X _548128 yes listing a d 1 ac b gt C d A yes Errors See portray_clause 2 See also portray_clause 2 4 1 127 max 3 Synopsis max A B C Description Succeeds if C is the maximum of A and B This predicate behaves as if it were defined as max A B C A gt B C A max _ B B Examples max 1 2 Max Max 2 yes max 2 1 Max Max 2 4 1 PREDICATES yes Errors Since A and B are evaluated errors may be thrown by eval 2 See also None 4 1 128 member 2 Synopsis member Element L
59. defined as follows copy_term T1 T2 asserta dummy_copy_functor T1 retract dummy_copy_functor FreshT1 FreshT1 T2 Examples copy_term foo A B Copy A _523696 B _524352 Copy foo _536064 _536080 68 CHAPTER 4 BUILT IN PREDICATES yes copy_term A B _522720 _523376 um Se ool yes copy_term A 99 A _522720 yes Errors None See also None 4 1 56 current_char_conversion 2 Synopsis current_char_conversion T1 T2 Description Succeeds if at some point char_conversion T1 T2 where T1 T2 has been used to update the character conversion table and this conversion is still valid i e hasn t been deleted with char_conversion T1 T1 Examples bagof T1 T2 current_char_conversion T1 T2 Bag no char_conversion p q yes bagof T1 T2 current_char_conversion T1 T2 Bag T1 _521856 T2 _522848 Bag p q yes char_conversion p p yes bagof T1 T2 current_char_conversion T1 T2 Bag 4 1 PREDICATES 69 no Errors type_error character T One of the arguments T1 or T2 was neither uninstantiated nor a character See also character 1 char_conversion 2 4 1 57 current_file_search_path 2 Synopsis current_file_search_path A D Description Succeeds if at some point add_file_search_path A D has been called to link the path alias A with
60. dynamic Examples assert public_pred yes public_procedure public_pred 0 yes 4 1 PREDICATES 165 Errors See procedure_property 2 See also procedure_property 2 private_procedure 1 4 1 177 put_byte 1 Synopsis put_byte B Description Behaves as if it were defined as follows put_byte Byte current_output S put_byte S Byte Examples See put_byte 2 Errors See put_byte 2 See also current_output 1 put_byte 2 4 1 178 put_byte 2 Synopsis put_byte S B Description Succeeds if the byte B can be written to the binary stream S 166 CHAPTER 4 BUILT IN PREDICATES Examples test_put_byte open test_file bin write Stream type binary put_byte Stream Byte close Stream Errors domain_error stream_or_alias S The argument S is not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error One of the arguments S or B was not instantiated permission_error output stream S There is a lack of permission to write to stream S permission_error output text_stream S The argument S refers to a text stream type_error byte B The argument B was instantiated but not a valid byte See also byte 1 4 1 179 put_char 1 Synopsis put_char C Description Behaves as if it were defined as follows put_char Char current_output S put_char S Char Examples
61. event is leashed or the goal has a spypoint then execution will stop and the user will be asked for a new command Creeping is the equivalent to single stepping found in debuggers for other programming languages carriage return Creep See above Display goal The current goal is passed to display 1 Fail Instead of continuing with normal execution the predicate fail 0 is called This only makes sense at call events Ancestor goals A list of the ancestor goals of the current goal are shown starting with the most recent ancestor then continuing back in time Each goal is written using write_term 2 along with the value of the flag debug_write_term_options This list may not be complete because the debugger cannot trace ancestors inside static predicates This means that the list which starts with the current goal s parent should it exist continues up to and not including the first ancestor which is a static goal Leap The flag trace is set to off and execution continues Trace messages will not be shown again until either the flag trace is set to on or execution progresses to a spypoint Use this command to leap from spypoint to spypoint without any trace messages in between No debug The predicate nodebug 0 is called and execution continues The effect of this is to turn of debugging Print goal The current goal is passed to print 1 This should be avoided if print 1 calls dynamic predicates when portraying as this cou
62. fy xfx xfy yfx xf yf yes Errors None See also current_op 3 op 3 infix_op_specifier 1 postfix_op_specifier 1 prefix_op_specifier 1 144 CHAPTER 4 BUILT IN PREDICATES 4 1 147 partial_list 1 Synopsis partial_list T Description Succeeds if T is a partial list The collection of partial lists is the smallest one satisfying i all variables are partial lists ii the atom is a partial list 111 if P is a partial list then so is _ P Examples partial_list _1_1 yes partial_list _ yes partial_list 1 yes Errors None See also var 1 4 1 148 peek_byte 1 Synopsis peek_byte 7B Description Behaves as if it were defined as follows peek_byte Byte current_input S peek_byte S Byte 4 1 PREDICATES 145 Examples See peek_byte 2 Errors See peek_byte 2 See also current_input 1 peek_byte 2 4 1 149 peek_byte 2 Synopsis peek_byte S 7B Description Succeeds if B would be the next byte read from the binary stream S Examples test_peek_byte open test_file bin read Stream type binary peek_byte Stream Byte get_byte Stream Byte close Stream Errors domain_error stream_or_alias S The argument S is not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error The argument S was not instantiated permission_error input
63. have at least one element in common Examples ord_intersect 1 2 3 8 4 5 yes ord_intersect 1 2 no Errors None See also ord_intersect 3 9 1 9 ord_intersect 3 Synopsis ord_intersect 01 02 03 Description Succeeds if the ordered set 03 is the set of all common elements of the ordered sets 01 and 02 Examples ord_intersect 1 2 3 3 4 5 0 O 3 yes ord_intersect 1 2 3 4 5 6 0 0 yes Errors None See also ord_intersect 2 9 1 PREDICATES 279 9 1 10 ord_powerset 2 Synopsis ord_powerset 01 702 Description Succeeds if the ordered set 02 is the powerset of the ordered set 01 Examples ord_powerset P P ENI yes ord_powerset 1 2 3 P P 0 11 1 2 1 2 31 1 31 21 2 31 31 yes Errors None See also None 9 1 11 ord_product 3 Synopsis ord_product 01 02 03 Description Succeeds if the ordered set 03 is the Cartesian product of the ordered sets 01 and 02 Examples ord_product 1 2 3 a b R R 1 a1 1 b 2 a 1 2 b 3 a 3 b yes ord_product a b 1 2 3 R R la 11 a 21 a 31 b 1 1 b 2 1 b 31 280 CHAPTER 9 THE ORDSET LIBRARY yes Errors None See also ord_all_unordered_pairs 3 9 1 12 ord_seteq 2 Synopsis ord_seteq 01 02 Description Succeeds if the ordered sets 01 and 02 are e
64. of each other Examples perm a b c L L a b c s L la c b s L b a c s L b c a EA ll y c a b ER i y c b a no Errors None See also None 8 1 12 perm2 4 Synopsis perm2 T1 T2 T3 T4 Description Succeeds if the first two arguments are a permutation of the second two arguments This predicate is defined as follows perm2 T1 T2 T1 T2 perm2 T1 T2 T2 T1 8 1 PREDICATES Examples assert zero A B perm2 0 _ A B gt ll _548608 _549280 w ll yes zero 5 0 yes zero AxB A 0 _547856 7 w Il A _547184 B 0 no Errors None See also None 8 1 13 remove_dups 2 Synopsis remove_dups L1 L2 Description 263 The list L2 is the result of taking the list L1 and removing all duplicated elements You will want the list L1 to be ground to avoid problems with unintended bindings This predicate is defined as follows remove_dups L1 L2 sort L1 L2 Examples remove_dups 1 1 1 L L 1 yes 264 CHAPTER 8 THE LISTS LIBRARY remove_dups 1 2 3 L L 1 2 3 yes Errors See sort 2 See also sort 2 8 1 14 rev 2 Synopsis rev L1 L2 Description Behaves as if it were defined as follows rev L1 L2 reverse L1 L2 Examples See reverse 2 Errors See reverse 2
65. past_end_of_stream S Tried to read past the end of the stream permission_error input stream S There is a lack of permission to read from stream S permission_error input text_stream S The argument S refers to a text stream type_error in_byte B The argument B was instantiated but not a valid input byte 146 CHAPTER 4 BUILT IN PREDICATES See also in_byte 1 get_byte 2 4 1 150 peek_char 1 Synopsis peek_char C Description Behaves as if it were defined as follows peek_char Char current_input S peek_char S Char Examples See peek_char 2 Errors See peek_char 2 See also current_input 1 peek_char 2 4 1 151 peek_char 2 Synopsis peek_char S C Description Succeeds if C would be the next character read from the text stream S Examples test_peek_char open test_file txt read Stream peek_char Stream C get_char Stream C close Stream 4 1 PREDICATES 147 Errors domain_error stream_or_alias S The argument Sis not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error The argument S was not instantiated permission_error input past_end_of_stream S Tried to read past the end of the stream permission_error input stream S There is a lack of permission to read from stream S permission_error input binary_stream S The argument S refers to a binary stream type_error i
66. prompt 4 query 4 radix 12 syntax 9 term 9 variable 9 warning 5 whitespace 14 367
67. t Replace with Unicode code 9 horizontal tab v Replace with Unicode code 11 vertical tab Replace with Unicode code 97 backslash c Ignore all subsequent whitespaces up to the next non whitespace charac ter C Here C is any whitespace character It is ignored Replace with Unicode code 127 delete C Here C is a character whose Unicode code modulo 32 is the Unicode code of the escape sequence These are the usual carat control codes for ASCII values 0 to 31 000 Here 000 is a sequence of from 1 to 3 octal digits Replace with the character represented by the Unicode code equal to the octal number uXXXXXX Here XXXXXX is a sequence of from 1 to 6 hexadecimal digits Re place with the character represented by the Unicode code equal to the hexadecimal number C Here C is any character not defined as an escape character The backslash is ignored and the entire escape sequence is replaced with C Numbers A number can be of the type integer or floating point Both types are of arbitrary precision See the documentation for the built in predicate eval 2 A number can be given in any radix from 2 binary to 36 The radix digits used to build numbers are the usual digits 0 to 9 and the alphabetical characters a to z or A to Z character case has no meaning The alphabetical characters are used for radices 11 to 36 An integer is an optional negative sign followed by a sequence of radix digits Exa
68. takes precedence over a conflicting default Examples write_term a b 1 2 VAR 26 O nl a b 1 2 VAR 26 yes write_term a b 1 2 VAR 26 lignore_ops true numbervars true quoted true nl a b 1 2 A1 OS yes Errors domain_error stream_or_alias S The argument S is not a stream term or a stream alias domain_error write_option Option One of the elements of the argu ment O Option was not a valid write option existence_error stream S Either the argument S does not refer to a currently open stream or S is not a current stream alias instantiation_error Either one of the arguments S or O is not instanti ated or an element of O was not ground permission_error output binary_stream S The argument S refers to a binary stream permission_error output stream S The argument S refers to an input stream type_error list 0 The argument 0 is not a list 4 2 DEFINITE CLAUSE GRAMMAR 217 See also add_portray 1 current_op 3 numbervars 3 read_term 3 4 1 241 version 0 Synopsis version Description Uses print_message 2 to display version information for Barry s Prolog and the Barry s Prolog Abstract Machine Examples version Abstract Machine version P1401 Prolog version P1A01 yes Errors None See also None 4 2 Definite Clause Grammar A Definite Clause Grammar DCG is a formalism simila
69. the name _ Named One of the following e A variable whose name starts with an upper case letter which is optionally followed by a sequence of characters where each char acter is either alphanumeric or _ The upper case letters that can start the name are those accepted by the built in predicate prolog_lexical_upper_case_letter 1 e A variable whose name starts with _ and is followed by a non empty sequence of characters where each character is either al phanumeric or _ The difference between these two types of variables is that two copies of the same named variable may refer to the same variable However two anonymous variables always refer to two different variables Examples Foo foo 10 CHAPTER 3 THE PROLOG LANGUAGE Atoms An atom is a symbol whose name is comprised of a sequence of characters which conform to one of the following cases e A lower case letter optionally followed by a sequence of alphanumeric characters The lower case letters that can start the name are those ac cepted by the built in predicate prolog_lexical_lower_case_letter 1 e A sequence comprised solely of characters drawn from either the fol lowing set amp lt gt V7 i QO t 1 273 pq i t gt 4 2G or a subset of all Unicode mathematical arrows and symbols Each possible character is accepted by the built in predicate prolog_lexical_symbol 1 Note The sequence is not a valid prefix for an atom name it s
70. value0 Assoc0 put_assoc key1 AssocO valuel Assoc1 get_assoc key0 Assoc1 Value0 get_assoc Key1 Assoc1 valuel findall Key Value get_assoc Key Associ Value Associations AssocO t key0 value0 t t Assocl t key0 value0 t t key1 valuel t t ValueO valueO Keyl keyl Key _573344 5 1 PREDICATES 235 Value _574336 Associations key0 value0 key1 valuel yes Errors None See also put_assoc 4 5 1 3 map_assoc 3 Synopsis map_assoc Pred OldAssoc NewAssoc Description For each element Key Value of OldAssoc there is an element Key NewValue of NewAssoc such that the call Pred Value NewValue succeeds The two association lists are structurally identical with the exception of the values Examples assert map_assoc_pred a 1 yes assert map_assoc_pred b 2 yes assert map_assoc_pred c 3 yes put_assoc b t b Assoc2 put_assoc a Assoc2 a Assoc3 put_assoc c Assoc3 c Assoc4 map_assoc map_assoc_pred Assoc4 Assoc5 get_assoc a Assoc5 1 get_assoc b Assoc5 2 get_assoc c Assoc5 3 Assoc2 t b b t t Assoc3 t b b t a a t t t Assoc4 t b b t a a t t t c c t t Assoc5 t b 2 t a 1 t t t c 3 t t yes 236 Errors None See also None CHAPTER 5 5 1 4 put_assoc 4 Synopsis THE Assoc LIBRARY put_assoc Key 0ldAssoc Value NewAssoc Description Succeeds if th
71. would represent f 1 2 3 Note that if we change 2 to be non associative xfx then the input in this example would lead to a syntax error The operators that are defined at system start up are shown in Table Sell 3 2 Exceptions Exceptions are used to report errors Prolog code can signal an error with throw 1 and handle an error with catch 3 The format of an error ex ception is error Error Details The term Error indicates the class of error and the term Details provides additional information intended to help pin point failure The predicate print_message 2 in combination with add_generate_message 1 can be used to print user friendly error messages What follows is a description of all the possible error exceptions error domain_error A B domain_error G N A B Argument num ber N of the goal G was the term B which was not of domain A error evaluation_error A existence_error G N A Argument num ber N of the goal G could not be evaluated due to reason A 18 Priority Associativity CHAPTER 3 THE PROLOG LANGUAGE Name 1200 1200 1200 1200 1159 1159 1159 1159 1159 1159 1100 1050 1000 900 700 700 700 700 700 700 700 700 700 700 700 700 700 700 700 700 500 500 500 500 400 400 400 400 400 400 400 400 200 200 200 200 xfx xfx fx fx fx fx fx fx fx y x y x y x y x y x y x y x y x y x y x yfx y x xfx xfy fy fy discontiguous d
72. 1 PREDICATES 291 See also get_code 2 292 CHAPTER 11 THE READIN LIBRARY Chapter 12 The readsent library To use the predicates in this library you will need to load the readsent fasl file One way to do this is with the following call ensure_loaded runtime readsent This library implements predicates that may be useful for reading sen tences of natural languages The code for these predicates is based on the Edinburgh public domain Prolog library 12 1 Predicates 12 1 1 case_shift 2 Synopsis case_shift MixedCaseCodes LowerCaseCodes Description The input list of character codes MixedCaseCodes is converted into the out put list LowerCaseCodes where each element of the input list which is an upper case alphabetic character code is converted into the equivalent lower case character code All other character codes are not altered This predicate behaves as if it were defined as follows case_shift Upper Mixeds Lower Lowers is_upper Upper Lower is Upper A a 1 case_shift Mixeds Lowers case_shift Lower Mixeds Lower Lowers case_shift Mixeds Lowers case_shift 293 294 CHAPTER 12 THE READSENT LIBRARY Examples case_shift AaBb Codes Codes 97 97 98 98 yes Errors As each element of MixedCaseCodes is evaluated errors may be thrown by eval 2 See also is_upper 1 12 1 2 chars_to_atom 3 Synopsis chars_to_atom Codes Input InputRe
73. 1 19 selectchk 3 Synopsis selectchk E1 L1 L2 Description This is a deterministic version of select 3 This predicate behaves as if it were defined as follows selectchk E1 L1 L2 once select E1 Li L2 Examples selectchk E 1 2 3 L E 1 L 2 3 no Errors None 268 CHAPTER 8 THE LISTS LIBRARY See also select 3 8 1 20 shorter_list 2 Synopsis shorter_list L1 L2 Description Succeeds if the list L1 is shorter in length than the list L2 This predicate can be used to exhaustively solve for L1 given L2 but not vice versa Examples shorter_list L 1 2 3 L 07 L 555216 L _555216 _ 555264 no shorter_list 1 2 L L _554544 _ 554592 _554640 _554656 no Errors None See also None 8 1 21 subseq 3 Synopsis subseq L1 L2 L3 8 1 PREDICATES 269 Description Succeeds if the list L2 is a sub sequence of the list L1 and those elements not in L2 are found in the list L3 The order of the elements in L1 is preserved in L1 and L2 Examples subseq a b L1 L2 Li L2 a b Li b L2 a Li a L2 b Li a b L2 no Errors None See also None 8 1 22 subseq0 2 Synopsis subseq0 L1 L2 Description Succeeds if the list L2 is a not necessarily proper sub sequence of the list L1 Examples subseg0 1 21 L L 1 2
74. 3333 yes format i k n dummy 1 2 1 2 yes format lLine 2n Nline n line line yes format p qn P a a 1 a a yes format r 16r n 24 24 30 18 yes format s 3s n Hello World Hello Wor yes format w n VAR 16 Q yes format 07n print Hello World Hello World yes Errors existence_error stream S The argument S was not an open stream domain_error empty_arguments The argument A was not of the cor rect length domain_error not_optional_argument C An optional argument was given to the format control character C domain_error not_less_than_zero N The numerical argument N was less than zero domain_error number_base N The numerical argument N given to r was not a valid base 108 CHAPTER 4 BUILT IN PREDICATES domain_error stream_or_alias S The argument S was not a stream term or an atom stream alias instantiation_error The arguments S A or C were not instantiated type_error atom T The argument to a was not an atom type_error atom_or_list C The argument C was neither an atom nor a list type_error character_code T The argument to c was not an character code type_error format_control C The character C is not a valid control character type_error integer T The given numerical argument was not an inte ger type_error list A Either the argume
75. 4 BUILT IN PREDICATES current_query_map_hook F no Errors None See also add_query_map_hook 1 current_query_map_hook 1 4 1 81 del_term_expansion 1 Synopsis del_term_expansion A Description Deregisters the predicate identified by the predicate indicator A 2 as a term expansion hook This predicate always succeeds Examples add_term_expansion foo yes current_term_expansion foo yes del_term_expansion foo yes current_term_expansion foo no Errors None See also add_term_expansion 1 current_term_expansion 1 term_expansion 2 4 1 82 delete_all 3 Synopsis delete_all Element Before After 4 1 PREDICATES 87 Description Deletes all occurrences of Element from the list Before giving the list After The members of Before are compared with Element using 2 This predicate is deterministic Examples delete_all 1 1 2 1 3 1 4 Lst Lst 2 3 4 yes Errors None See also delete_all_equal_terms 3 4 1 83 delete_all_equal_terms 3 Synopsis delete_all_equal_terms Element Before After Description Deletes all occurrences of Element from the list Before giving the list After The members of Before are compared with Element using 2 This predicate is deterministic Examples delete_all_equal_terms 1 1 2 1 Lst Lst 2 yes delete_all_equal_terms _ 1 2 1 Lst Lst 1 2 1
76. 4 2 X 37 yes X is 14480694097861998019 100 gt gt 64 2 X 314 7 yes Since part E is an arbitrary precision integer the magnitude of a floating point number s exponent can be arbitrarily large The arithmetic functors which represent the bit wise operations lt lt El E2 E1 E2 gt gt gt E1 E2 E1 E2 and E only work on integers greater than or equal to zero There is also the issue of word size With these operations the smallest multiple of the target machine word size which is large enough to hold all of the given arguments is the result word size So if you were to calculate the logical not negation inversion of zero then on a 64 bit machine the result would be a positive integer of precision 64 bits with all bits set to one whereas on a 32 bit machine the result would be a positive integer of precision 32 bits with all bits set to one What follows is a list of arithmetic functors and their evaluation abs E Calculates the absolute value of the argument E1 E2 Calculates the addition of the arguments atan E Calculates the arc tangent of the argument in radians This is an elementary function found in elementary_functions fasl 4 1 PREDICATES 93 gt E1 E2 Calculates the bit wise and of the two arguments Both ar guments must be integers greater than or equal to zero E Calculates the bit wise not negation inversion of the
77. 40 CHAPTER 4 BUILT IN PREDICATES Examples op 200 xfx yes op 300 xfx 4 yes write_canonical a b amp c nl amp a b c Errors domain_error operator_priority P The argument P was either less than O or greater than 1200 domain_error operator_specifier S The argument S was not a valid operator specifier instantiation_error One of the arguments P S or A was not ground permission_error create operator A An attempt was made to cre ate the operator A but this couldn t be done permission_error modify operator An attempt was made to mod ify the operator type_error atom S The argument S was not an atom type_error integer P The argument P was not an integer type_error list A The argument A was not an atom and it was not a list See also current_op 3 infix_op_specifier 1 postfix_op_specifier 1 prefix_op_specifier 1 4 1 144 open 3 Synopsis open F M S Description Equivalent to open F M S 4 1 PREDICATES 141 Examples See open 4 Errors See open 4 See also open 4 4 1 145 open 4 Synopsis open F M S 0 Description Opens the file specified by the path F mode M and options 0 The result is the stream term S which can be used to input or output data The argument F is passed to absolute_file_name 2 and it is the result of this that is the specified file The argument M must be one of the foll
78. 47 4 120 atom Canea La iaa ao e ae 48 4 1 30 ArOm_ Inde Bi oos es acp eeu oep ee Ee 49 A L3l atom Length le cocino cara a ae 50 401 32 aconte ono howe aa dl 2S 51 4 183 DENSA a 51 LL bagof 3 eco se 52 4 1 85 Break 0 o 2 4 ice eR EAR ER Oe EEL ae ee 53 AAO PEGG ti oo a Eee ee a ee eS 54 Bi oe is es we a a se Bd de 55 MBS Sead Li ee oo A e t 55 HBO LI ra a OE Ree aw 56 AAA callable termal ooo ao ee Ae ws 57 ALAL CAE ia Ao kw Poe BR ee OA 57 AAG char Cga oi a woe a A a AS 58 CONTENTS 4 1 43 4 1 44 4 1 45 4 1 46 4 1 47 4 1 48 4 1 49 4 1 50 4 1 51 4 1 52 4 1 53 4 1 54 4 1 55 4 1 56 4 1 57 4 1 58 4 1 59 4 1 60 4 1 61 4 1 62 4 1 63 4 1 64 4 1 65 4 1 66 4 1 67 4 1 68 4 1 69 4 1 70 Alel AZ eN 4 1 74 4 1 75 4 1 76 AL 4 1 78 4 1 79 4 1 80 4 1 81 4 1 82 4 1 83 4 1 84 4 1 85 4 1 86 v char conversion 2 2 12 46 484 ee EER EES 59 Chatacion l cok eek Ae eRe ES Ee 60 character code 1 cj bh ea e E 60 CLAS o so Kiko eR ee ee EES e ee 61 e s y i feds BR ee BR Go ae hed ee E i 62 GLOBE Dok ewe eee o A A E 62 COMPALE Si looks ds Sth be Soe RG BS 63 COMpanmd l A a ee e ORS hy 64 concatable_atom l o 64 Conjunction 9737 2 crios r ies e soda e 65 cORSUIE o sr ia aa we BOE ee 66 COMPEEE char 2 co de e Sh ee ee eS 66 Copy Tere Di o a hee PA ed 67 current_char_conversion 2 68 current_file_search_path 2 69 current_generate_message 1 70 CHP
79. 57 57 yes Errors instantiation_error Both arguments were uninstantiated See also atom_codes 2 number_codes 2 4 1 132 n1 0 Synopsis nl Description Equivalent to current_output S n1 S 4 1 PREDICATES 131 Examples See n1 1 Errors See n1 1 See also current_output 1 n1 1 4 1 133 n1 1 Synopsis n1 5 Description Behaves as if it were defined as follows nl S put_code S 13 put_code S 10 flush_output S Examples print a nl print user_error b nl user_error a b yes Errors instantiation_error The argument S was not instantiated domain_error stream_or_alias S The argument S was neither a stream term nor an alias existence_error stream S The argument S referred to a nonexistent stream permission_error output binary_stream S The argument S referred to a binary stream permission_error output stream S The argument S referred to an in put stream 132 CHAPTER 4 BUILT IN PREDICATES See also flush_output 1 put_code 2 4 1 134 number 1 Synopsis number T Description Succeeds if T is a number A number is either a floating point number or an integer This predicate behaves as if it was defined as follows number T integer T number T float T Examples number 9 yes number 9 0 yes number nine no Errors None See also float 1 integer 1 4 1 135 numberv
80. A The argument A was not an atom See also current_message_hook 1 del_message_hook 1 print_message_lines 3 4 1 8 add_portray 1 Synopsis add_portray A 30 CHAPTER 4 BUILT IN PREDICATES Description Registers the predicate identified by the predicate indicator A 2 as a portray hook A portray hook is a predicate with arity 2 the first argument being a stream term and the second argument the term to be portrayed A call of write_term S T 0 where the list 0 contains the element portray true such as in the case of print 2 will for each subterm U of T in turn search for a portray hook which succeeds when passed the stream term S and U Should such a portray hook exist then the writing of U as a sub process of the writing of T is complete Should no such portray hook exist then U is written as it normally would be Portray hooks are found in the order that they are registered with add_portray 1 The subsequent registration of an already registered hook has no effect Examples assert my_portray S foo write S goo_not_foo S _524784 yes print foo nl foo yes add_portray my_portray yes print foo nl goo_not_foo yes del _portray my_portray yes print foo nl foo yes Errors instantiation_error The argument A was not instantiated type_error atom A The argument A was not an atom See also current_portray 1 del_portray 1
81. Barry s Prolog Reference Manual amp User Guide Version P1A02 Barry Watson ii Copyright 2013 2014 Barry Watson All rights reserved No part of this publication may be reproduced stored in an information retrieval system or transmitted in any form or by any means electronic mechanical photocopying recording or otherwise without the prior permission of Barry Watson http www barrywatson se Contents 1 Introduction 1 LI Aborto corsario ee eee eee Ea 1 1 2 Notations so sesa bebe eee SA RAR Cee S 1 1 21 Types 20 sicpi ea A ERO eo Be i 1 1 2 2 Predicate reference 000 eee 1 1 2 3 Modedeclaration 0 008 2 ae 2 2 Using Barry s Prolog 3 2A Getting Started io sso been wae ee eed we dee 3 22 QUIRES we ch we hee Pewee he ene E 4 Did Modafan s iere aoe eh amp eae a me Ae ep eg ed 5 2 4 Loading Prolog Files 0 o pop a 5 24 1 discovtignoue 1 so et eA ae pior pe bos rs 5 2A o sd os bok ek wh See hee eee T 5 24 3 nsure loaded 1 e s ces de he be me es 6 Za ee AM x a ees geal et elas SO ee ee 6 24 5 Anmtrializabtion Ll lt rocio ora 6 ZO Bucal L essegi ee RO ee eS 6 DAY Prolog Term e cose AR 7 20 Interrupting Execution i e i so 6a ca bk Rhee Pe ad 7 Doll ADO 6 455 4 Gee a BEM A RG Phe AES 7 2058 CONNUE o s sorg t we hee ew ee ly whee ee AHS A T 20 Seb debug Mae a ce ma disa we ka n a A ee 8 20d Ert POOE ooe oe a eoe Ro Dap ee e e a a 8 2 5 5 Clear trace
82. CDF 5 0 yes sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 0 00 015 as LinearInterpolationCalifornia LinearInterpolationCalifornia 5 0 yes sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 0 5 0 0 O ClosestElement ClosestElement 5 0 yes sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 0 5 0 0 1 LinearInterpolationHydrologist LinearInterpolationHydrologist 5 5 yes sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 0 1 0 1 Wiebull Wiebull 5 5 yes 13 1 PREDICATES 329 sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 1 1 0 1 ModeEstimate ModeEstimate 5 5 yes sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 3 8 1 4 0 1 NormalDistributionEstimate NormalDistributionEstimate 5 5 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error At least one of the arguments L Q P1 P2 P3 or P4 was an uninstantiated variable type_error list L The argument L was not a list Also as almost all of the arguments are evaluated errors may be thrown by eval 2 See also None 13 1 22 sample_semi_interquartile_range 2 Synopsis sample_semi_interquartile_range L Result Description Result is the sample semi interquartile range of the list of numbers L This predicate behaves as if it were defined as sample_semi_interquartile_range L Result sample_interquar
83. DEBUG PREDICATES 347 Examples add_spypoint fact 2 yes debugging Debugging is off Tracing is off Spying on the following list of predicates fact 2 yes Errors instantiation_error The argument PI was not ground type_error predicate_indicator PI The argument PI was not a valid predicate indicator See also debugging 0 spy 1 14 3 2 debug 0 Synopsis debug Description Sets the flag debug to the value on and the flag trace to the value of f Examples debug yes debugging Debugging is on Tracing is off Spying on the following list of predicates fact 2 yes Errors None See also nodebug 0 notrace 0 trace 0 348 CHAPTER 14 DEBUG 14 3 3 debugging 0 Synopsis debugging Description Display the status of the debugging flags and a list of the spypoints which have been placed on predicates Examples debugging Debugging is on Tracing is off Spying on the following list of predicates fact 2 yes Errors None See also debug 0 spy 1 trace 0 14 3 4 leash 1 Synopsis leash Mode Description Configures the debugger to stop upon certain trace events prompt for a debugging command from the user then execute the given command These trace events correspond to the the debugger entering and leaving a predicate namely on calling successful exit redo upon backtracking complete failure and upon the throwing of an excep
84. ES 103 Examples float 9 no float 9 0 yes Errors None See also None 4 1 97 flush_output 0 Synopsis flush_output Description Flushes the current output stream This predicate behaves as if it was defined as follows flush_output current_output S flush_output S Examples flush_output yes Errors None See also flush_output 1 4 1 98 flush_output 1 Synopsis flush_output S 104 CHAPTER 4 BUILT IN PREDICATES Description Flushes the stream identified by S Examples open test txt write 0 print 0 foo flush_output 0 close 0 0 stream 3 yes Errors instantiation_error The argument S was not instantiated domain_error stream_or_alias S The argument S was neither a stream term nor an alias atom existence_error stream S The argument S did not identify an existing stream permission_error output stream S The argument S was not an out put stream See also flush_output 1 4 1 99 format 2 Synopsis format C A Description Equivalent to current_output S format S C A Examples See format 3 Errors See format 3 4 1 PREDICATES 105 See also current_output 1 format 3 4 1 100 format 3 Synopsis format S C A Description Formats the control string C with the arguments A and writes the result onto the stream S C is either a list of characters or an atom A is
85. Errors None See also nth0 3 260 8 1 8 ntho 4 Synopsis nth0 N L1 E L2 nthO N L1 E L2 Description CHAPTER THE LISTS LIBRARY Succeeds if the list L1 at index N contains the element E and the remainder of the list is L2 The first element has index 0 This predicate is deterministic Examples nth0 3 L x a b c d L a b c x d yes nthO N a b c d c L N 2 L a b d yes Errors None See also nth1 4 8 1 9 nth1 4 Synopsis nth1 N L1 E L2 nthi N L1 E L2 Description Succeeds if the list L1 at index N contains the element E and the remainder of the list is L2 The first element has index 1 This predicate is deterministic 8 1 PREDICATES 261 Examples nthi 4 L x a b c d L a b c x d yes nthi N a b c d c L N 3 a b d EA Il h yes Errors None See also nth0 4 8 1 10 numlist 3 Synopsis numlist Low High L Description Succeeds if the list L is the sequence of numbers from Low to High sorted in numerical order Examples numlist 1 3 L L 1 2 3 yes numlist 4 3 L no Errors Since Low and High are evaluated errors may be thrown by eval 2 See also None 262 CHAPTER 8 THE LISTS LIBRARY 8 1 11 perm 2 Synopsis perm L1 L2 Description Succeeds if the two arguments are lists which are permutations
86. Errors instantiation_error The argument F was not instantiated 4 1 PREDICATES 177 See also absolute_file_name 2 consult 1 2 4 1 192 repeat 0 Synopsis repeat Description Succeeds and creates a looping choice point Behaves as if defined as follows repeat repeat repeat Examples skip_to_end_of_text_file Stream repeat get_char Stream _ at_end_of_stream Stream failure loops at repeat 0 L remove choicepoint Errors None See also None 4 1 193 retract 1 Synopsis retract T Description Removes a dynamic clause from the clause store which unifies with the ar gument T If the argument is not a compound term with a principle functor of 2 then this call will behave as that of a new call of retract T true This predicate will succeed as many times as there are clauses in the clause store which unify with T 178 CHAPTER 4 BUILT IN PREDICATES Examples assert g 1 assert g 2 yes g X X 1 gt lt ll N no retract g X fail no clause g _ C no Errors instantiation_error T he head of the argument clause T was not instanti ated permission_error access static_procedure F N The head of the ar gument clause T has a predicate indicator of F N and this identifies a static procedure type_error callable H The head of the argument clause T was H and this is not a callable term See also
87. Examples See portray_clause 2 Errors See portray_clause 2 See also current_output 1 portray_clause 2 4 1 158 portray_clause 2 Synopsis portray_clause S C Description Pretty prints the clause C on the stream S This predicate is very useful for programs which generate Prolog code Examples current_output S portray_clause S a X b X c X Y d X gt e X a A b A 1 c A B s d A gt e A S stream 1 _553488 _557056 lt ps oul yes 4 1 PREDICATES 153 Errors This predicate uses write 2 which may raise errors See also None 4 1 159 postfix_op_specifier 1 Synopsis postfix_op_specifier T Description Succeeds if T is an postfix operator specifier Examples findall 0 postfix_op_specifier 0 L _522304 D L xf yf1 yes Errors None See also current_op 3 op 3 op_specifier 1 infix_op_specifier 1 prefix_op_specifier 1 4 1 160 predicate_indicator 1 Synopsis predicate_indicator P Description Succeeds if P is a valid predicate indicator P unifies with F N where F is an atom and N is an integer that is greater than or equal to 0 and less than the value of the flag max_arity 154 CHAPTER 4 BUILT IN PREDICATES Examples predicate_indicator predicate_indicator 1 yes predicate_indicator X no Errors None See also atom 1 integer 1 4 1 161 predication 1 Sy
88. ILT IN PREDICATES Examples prolog_lexical_digit 0 5 yes prolog_lexical_digit 5 no between 0 16 22ff Code prolog_lexical_digit Code put_code Code fail nl 0123456789 Code _514512 yes Errors None See also prolog_lexical_lower_case_letter 1 prolog_lexical_symbol 1 prolog_lexical_upper_case_letter 1 prolog_lexical_ws 1 4 1 170 prolog_lexical_letter 1 Synopsis prolog_lexical_letter Code Description Succeeds if the character code Code represents an alphabetical character Behaves as if it were defined as follows prolog_lexical_letter CodePoint prolog_lexical_lower_case_letter CodePoint prolog_lexical_upper_case_letter CodePoint Mey Examples prolog_lexical_letter 0 p h yes prolog_lexical_letter 0 P yes 4 1 PREDICATES 161 Errors None See also prolog_lexical_upper_case_letter 1 prolog_lexical_lower_case_letter 1 4 1 171 prolog_lexical_lower_case_letter 1 Synopsis prolog_lexical_lower_case_letter Code Description Succeeds if the character code Code represents an alphabetical character that can be used to start a Prolog atom name Examples prolog_lexical_lower_case_letter 0 p yes prolog_lexical_lower_case_letter 0 P no If your terminal can display the Latin 1 codepage characters you can try the following between 0 16 22ff Code prolog_lexical_lower_case_lett
89. INDEX key_pair 1 122 keysort 2 122 last 2 256 leash 1 348 length 2 123 less_than 2 40 less_than_equal 2 40 list_to_ord_set 2 273 listing 0 124 listing 1 124 listing 2 125 map_assoc 3 235 max 3 126 member 2 127 message_hook 3 127 min 3 129 name 2 130 nextto 3 257 n1 0 130 n1 1 131 nmember 3 258 nmembers 3 258 nodebug 0 8 349 nonvar 1 134 normal_cdf 4 316 normal_pdf 4 317 normal_quantile 4 318 nospy 1 350 nospyal1 0 350 notrace 0 351 nth0 3 135 nth0 4 260 nth1 3 259 nth1 4 260 number 1 132 number_base_codes 3 136 number_chars 2 136 number_codes 2 137 numbervars 3 132 numlist 3 261 once 1 138 op 3 7 15 139 op_specifier 1 143 open 3 140 open 4 141 ord_all_nonempty_subsets 2 274 ord_all_subsets 2 274 ord_all_subsets 3 275 ord_all_unordered_pairs 3 276 ord_disjoint 2 276 ord_insert 3 277 ord_intersect 2 277 ord_intersect 3 278 ord_powerset 2 279 365 ord_product 3 279 ord_seteq 2 280 ord_subset 2 280 ord_subtract 3 281 ord_symdiff 3 281 ord_union 3 282 p_member 3 248 p_to_s_graph 2 249 p_transpose 2 249 partial_list 1 144 peek_byte 1 144 peek_byte 2 145 peek_char 1 146 peek_char 2 146 peek_code 1 147 peek_code 2 148 perm 2 262 perm2 4 262 phrase 2 149 phrase 3 149 population_mean_confidence_interval 4 318 portray 2 151 portray_clause 1 151 portray_clause 2 152 postfix_op_specifier 1 153 predicate_indicator
90. N was an unin stantiated variable type_error integer I Either the argument M or the argument N did not evaluate to an integer Also as the arguments X M and N are evaluated errors may be thrown by eval 2 See also None 13 1 5 f_pdf 4 Synopsis f_pdf X M N Answer 13 1 PREDICATES 315 Description Answer is the probability density at Y X where Y is a random variable distributed according to the F distribution with M numerator and N de nominator degrees of freedom Examples f_pdf 1 100 100 Answer Answer 1 989731 yes f_pdf 3 1 1 Answer Answer 0 045944 yes Errors domain_error not_less_than_one I Either the argument M or the ar gument N was less than 1 domain_error not_less_than_zero X The argument X was less than 0 instantiation_error At least one of the arguments X M or N was an unin stantiated variable type_error integer I Either the argument M or the argument N did not evaluate to an integer Also as the arguments X M and N are evaluated errors may be thrown by eval 2 See also None 13 1 6 f_quantile 4 Synopsis f_quantile P M N Zp Description Zp is the P quantile 0 lt P P lt 1 of the F distribution with M numerator and N denominator degrees of freedom 316 CHAPTER 13 THE STATISTICS LIBRARY Examples f_quantile 0 9 9 9 Zp Zp 2 440334 yes Errors domain_error not_greater_than
91. OR ex 183 4 1 200set_stream_position 2 184 dll SUISECOL S ak e a eR cir ee a aa ke 2 186 a 2s on ok bow ee ee ee aa beak ee we 187 4203 sores sine Lo ee ee ee e a a 188 4 20a Statistics ts a he ea ee oe ee 189 LL BUOStESII L fo RG PR ee eS pe ee Ba oS 190 4 1 206stream_alias 2 191 4 1 207 stream_position_byte_count 2 192 4 1 208 stream_position_character_count 2 192 4 1 209 stream_position_line_count 2 193 4 1 210 stream_position_line_position 2 193 4 1 211stream_property l 194 4 1212 Stream propertyl2 ocio es eS 194 ALBERDI pr ido e A 196 AZUL SHDSUMEBZCRR 2 8605 a lhe eee Gh ae Ge 198 Ale le Subsumes LSO o e ek oe ee OE RS ea ae 198 A 2 o errors 0 ek e ke ae ee Se hoe ew 199 4 1 217Term comparison 02 4 199 4 1 218term_expansion 2 00 4 201 CONTENTS ix 4 2 4 3 A oe eb eee eA ee BAe REDE SS 201 Ah POU RPGS LO ca ck et Ba ee ek A SR Fo Ee 202 A L222 ungetcpyte i ik hehe he ee eS ES 202 AA 22M A ee ee a Ee A ES 203 AN 223 eget Cher Lois a ea ee he a ee ot 204 ALIADO chery a RR eee ek Be 204 AM 220 ungeteode lo he ee aa O e 205 AL 226unpet Cod 2 ok ke ke ee he A we e E RE ee a 206 AMOR St o e a bk be ow eo BO oe he wl betel amp x 207 ALIS S972 2 ka ht a OE ee Rw ae ER ee 207 41 229 unity with _occirecheck 2 o ce c regen aine ee 208 ALUS E RA 209 ALOE e ai a a a ed SS
92. REDICATES 4 1 139 number_base_codes 3 Synopsis number_base_codes N B L Description Succeeds if the name of the number N corresponds to the list of character codes L represented in base B Acceptable values for B satisfy both 2 lt B and B lt 36 Examples number_base_codes 99 16 L atom_codes A L L 49 54 39 54 51 A 1663 yes Errors domain_error number_base B The argument B was an integer but it was either less than 2 or greater than 36 instantiation_error Either the argument N or the argument B was an uninstantiated variable type_error integer B The argument B was instantiated but it was not an integer type_error number N The argument N was instantiated but it was not a number See also number_codes 2 name 2 4 1 140 number_chars 2 Synopsis number_chars N L number_chars N L Description Succeeds if the name of the number N corresponds to the list of characters L 4 1 PREDICATES 137 Examples number_chars N 3 1 4 N 3 14 yes number_chars 3 14 C C 3 1 4 yes Errors instantiation_error Either both arguments were uninstantiated or N was uninstantiated and L was not ground type_error number N The argument N was instantiated but it was not a number type_error list L The argument L was instantiated but it was not a list type_error character E The argument L contained an element E w
93. See put_char 2 4 1 PREDICATES 167 Errors See put_char 2 See also current_output 1 put_char 2 4 1 180 put_char 2 Synopsis put_char S C Description Succeeds if the character C can be written to the text stream S Examples test_put_char open test_file txt write Stream put_char Stream C close Stream Errors domain_error stream_or_alias S The argument S is not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error One of the arguments S or C was not instantiated permission_error output stream S There is a lack of permission to write to stream S permission_error output binary_stream S The argument S refers to a binary stream type_error character C The argument C was instantiated but not a valid character See also character 1 168 CHAPTER 4 BUILT IN PREDICATES 4 1 181 put_code 1 Synopsis put_code C Description Behaves as if it were defined as follows put_code Code current_output S put_code S Code Examples See put_code 2 Errors See put_code 2 See also current_output 1 put_code 2 4 1 182 put_code 2 Synopsis put_code S C Description Succeeds if the character code C can be written to the text stream Examples test_put_code open test_file txt write Stream put_code Stream C close Stream 4 1 PREDICATES 169 Errors
94. Singleton variables H G F E Singletons 240 CHAPTER 6 THE BUP LIBRARY File home bwat BarrysProlog bin linux_x86_64 grammar pl Position start of term line number 20 column number 0 Singleton variables E yes We now need to define vocabulary 4 For the purposes of this example we ll just add a noun and a verb The format of the predicate is specified to be vocabulary NonTerminal ArgumentList Input Remainder Input and Remainder together form a difference list It is the difference between these lists that is the terminal which is to be parsed as a type of NonTerminal with its argument in the list ArgumentList We can see from the following two clauses how to state that horse is a noun and dislikes is a verb assert vocabulary noun n horse horse Rest Rest Rest _553920 yes assert vocabulary verb v dislikes dislikes Rest Rest Rest _554880 yes We now have everything in place so we can test the new dictionary entries defined by vocabulary 4 bup_goal s Tree the horse dislikes the dog Tree s np d the n horse vp v dislikes np d the n dog yes There is another option that can be given which caches parse results There are in fact two caches e A cache of successful parses Each entry corresponds to a call of bup_goal 4 described later which succeeded e A cache of failed parses
95. T2 T3 where the cut is limited in scope to this goal i e should T1 succeed and T2 fail there will be no back track to T3 Examples true gt print YES nl YES yes fail gt print NO nl no true gt print YES nl fail print NO nl YES 7 no 118 CHAPTER 4 BUILT IN PREDICATES Errors None See also 12770 4 1 114 in_byte 1 Synopsis in_byte B Description Succeeds if B is a valid input byte Behaves as if it were defined as follows in_byte Byte integer Byte Byte gt 1 Byte lt 255 Examples in_byte 99 yes Errors None See also None 4 1 115 in_character 1 Synopsis in_character C Description Succeeds if C is a valid input character that is to say C is either the atom end_of_file or a valid character 4 1 PREDICATES 119 Examples in_character end_of_file yes in _character f yes in character ff no Errors instantiation_error The argument C was not instantiated See also character 1 4 1 116 in_character_code 1 Synopsis in_character_code C Description Succeeds if C is a valid input character code that is to say C is either 1 or a valid character code Examples in_character_code 1 yes in character_code 99 yes in character_code 99 7 no Errors None See also character_code 1 120 CHAP
96. TER 4 BUILT IN PREDICATES 4 1 117 infix_op_specifier 1 Synopsis infix_op_specifier T Description Succeeds if T is an infix operator specifier Examples findal1 0 infix_op_specifier 0 L _522304 0 L xfx xfy yfx yes Errors None See also current_op 3 op 3 op_specifier 1 postfix_op_specifier 1 prefix_op_specifier 1 4 1 118 integer 1 Synopsis integer T Description Succeeds if T is an integer Examples integer 9 yes integer 9 0 no Errors None 4 1 PREDICATES 121 See also None 4 1 119 io_mode 1 Synopsis io_mode T Description Succeeds if T is a valid I O mode used by open 4 Examples findall M io_mode M Modes M _522304 Modes read write append yes Errors None See also open 4 4 1 120 is 2 Synopsis T is E Description Succeeds if T is unified with to the arithmetic evaluation of E which was calculated with eval 2 Examples X is 1 2 X 3 yes X is 2 3 122 CHAPTER 4 BUILT IN PREDICATES X 8 7 yes Errors See eval 2 See also eval 2 4 1 121 key_pair 1 Synopsis key_pair T Description Succeeds if T is a key pair term The collection of key pairs consists of all compound terms with principle functor 2 Examples key_pair a 1 yes key_pair 99 no key_pair X Errors None See also keysor
97. TES Description This predicate is used internally by generate_message_lines 3 Behaves as if it were defined as follows generate_message_line gt generate_message_line Control Arguments T gt Control Arguments generate_message_line T generate_message_line write_term Term Options T gt write_term Term Options generate_message_line T Examples None Errors None See also generate_message_lines 3 4 1 103 generate_message_lines 3 Synopsis generate_message_lines 7A 7B C Description This predicate is used internally by print_message 2 Behaves as if it were defined as follows generate_message_lines gt generate_message_lines H T gt generate_message_line H n1 generate_message_lines T Examples None 4 1 PREDICATES 111 Errors None See also generate_message_line 3 print_message 2 4 1 104 get_byte 1 Synopsis get_byte B Description Behaves as if it were defined as follows get_byte Byte current_input S get_byte S Byte Examples See get_byte 2 Errors See get_byte 2 See also current_input 1 get_byte 2 4 1 105 get_byte 2 Synopsis get_byte S B Description Reads a byte B from the binary stream S 112 CHAPTER 4 BUILT IN PREDICATES Examples test_get_byte open test_file bin read Stream type binary get_byte Stream 16 de get_byte Stream 16 ad ge
98. TeNnt input l e cics eet oaei ak a at do 70 current_message_hook 1 71 c rrent OP 8 fice ea wh Le Se 72 Current CULPUUST ac ei whe Ba is i 72 Current portray i lt eeds oor ee a 73 current_portray_message l 74 current _predicate l corsa AA eS 74 current prolog flag 2 oe o pe wee ee es 75 current_query_class_hook 1 76 current_query_input_hook 1 76 current_query_map_hook 1 77 current_term_expansion 1 78 Ub AUTO a RG he a SR Ae ee woe ee 78 A oben Bae be a we ee bee bee ee ed 79 del file search pathy o so m eo akg wee es 80 del_generate_message 1 81 del_message_ho0k 1l o o 81 del portray Loi e Bah BS 82 del_portray_message l 83 del_query_class_ho0k 1 84 del_query_input_ho0k 1 84 del_query_map_hook 1 85 del_term_expansion 1 86 delete ALIS pu Ge g a eR AA ee 86 delete_all_equal_terms 3 87 delete_deterministically 3 88 Wighinetion 72 2 6 4 6 ee bea Pk a 88 CPSP ey aa old Oo ae Dt oe he he 89 vi CONTENTS Aer display 2 coin he MRERER EH ELSES 89 A188 Det Zocor tee ee ee bee Ae 90 4 1 89 ensure_loaded l 90 AO AU ne A dn ee wn eck De 91 4 1 91 Existential quantification 2 99 Ale Sepend temisys 2 op se nore Poi e e haw 99 ALOS aay Oo cria Boh ee
99. _byte_count Position Value The number of bytes read from or written to the stream is Value stream_position_character_count Position Value The number of char acters read from or written to the stream is Value stream_position_line_count Position Value The number of lines read from or written to the stream is Value The line count for a newly opened file is 1 A line count of 0 is not valid stream_position_line_position Position Value The position in the current line is Value The first position in a line is 0 The argument Position is used to set the following internal counters that are updated upon the completion of a stream I O operation byte_count Updated upon get_byte 2 put_byte 2 and unget_byte 2 character_count Updated upon get_code 2 put_code 2 unget_code 2 get_char 2 put_char 2 and unget_char 2 line_count Updated upon get_code 2 put_code 2 unget_code 2 get_char 2 put_char 2 and unget_char 2 line_position Updated upon get_code 2 put_code 2 unget_code 2 get_char 2 put_char 2 and unget_char 2 As can be seen it makes little sense changing the value of byte_count for a text stream and likewise changing the character_count for a binary stream is meaningless It should be noted that changing the position of a Unicode text stream could place the current position in the middle of a character code and this could lead to errors Examples open test_set_stream_position write OutStr
100. _one P The argument P was greater than 1 domain_error not_less_than_one I Either the argument M or the ar gument N was less than 1 domain_error not_less_than_zero P The argument P was less than 0 instantiation_error At least one of the arguments P M or N was an unin stantiated variable type_error integer I Either the argument M or the argument N did not evaluate to an integer Also as the arguments P M and S are evaluated errors may be thrown by eval 2 See also None 13 1 7 normal_cdf 4 Synopsis normal_cdf X M S Answer Description Answer is the probability that Y lt X where Y is a random variable distributed according to the normal distribution with mean M and variance S Examples normal_cdf 0 O 1 Answer Answer 0 5 yes 13 1 PREDICATES 317 Errors domain_error not_less_than_zero S The argument S was less than 0 instantiation_error At least one of the arguments X M or S was an unin stantiated variable Also as the arguments X M and S are evaluated errors may be thrown by eval 2 See also None 13 1 8 normal_pdf 4 Synopsis normal_pdf X M S Answer Description Answer is the probability density at Y X where Y is a random variable distributed according to the normal distribution with mean M and variance S Examples normal_pdf 0 O 1 Answer Answer 0 398942 yes normal_pdf 0 0 4 Answer Answer 0 199471
101. a list Each character of the control string is written on the stream unless it is the character which is the escape character The next character after the escape is the control character and determines the action to be taken Some actions take an argument given as an element of a list passed via the argument A The order of the elements of this list matches the order of the argument taking control actions in C i e the fourth argument taking control action of C uses the fourth element of A There is another type of argument numerical arguments which are given between the escape and control characters or in the arguments list which is signified by placing the character between the escape and control characters This gives three different methods of argument passing format S a argument Control character a takes an argument in the arguments list format S 23a argument Control character a takes an argument in the arguments list and a numerical argument 23 in the control string format S a 23 argument Control character a takes an argument and a numerical argument in the arguments list Here is the list of valid control characters numerical arguments are taken by those characters which are prefixed by lt N gt a Interpret the argument as an atom and print it without quoting lt N gt a Interpret the argument as an atom and print its first N characters without quoting c Interpret the arg
102. able Chapter 2 Using Barry s Prolog 2 1 Getting Started The system is started with the command BarrysProlog When this com mand is given you should see something similar to the following prolog herbrand BarrysProlog Prolog Copyright C 2012 2014 Barry Watson All rights reserved Abstract Machine version P1A01 Prolog version P1A01 Welcome BarrysProlog file consulted One of the tasks performed by the system when it is initialising is the loading of the file named BarrysProlog which is found in your home directory The contents of this file can be used to configure the system to your liking load additional files set flags etc If this file doesn t exist then the following will be seen instead prolog herbrand BarrysProlog Prolog Copyright C 2012 2014 Barry Watson All rights reserved Abstract Machine version P1401 Prolog version P1A01 Welcome No BarrysProlog file found You should create this file and add at least the following lines to ensure trouble free usage 4 CHAPTER 2 USING BARRY S PROLOG add_file_search_path runtime opt BarrysProlog runtime add_file_search_path examples opt BarrysProlog examples ensure_loaded runtime elementary_functions ensure_loaded runtime special_functions 7 End of home prolog BarrysProlog The first two lines assume that BarrysProlog has been installed in the direc tory opt s
103. aces instead of two asterisks which indicate that this is not a spypoint 0 This is the global invocation count It is incremented on each sub goal call the debugger makes Static predicates do not increment the counter when calling sub goals This counter is set to zero before the top level loop tries to satisfy a query This is the depth count and should be interpreted as a count of the number of dynamic parent goals the current goal has This is set to zero upon two events when the global invocation count is set to zero and every time a static predicate passes control to a dynamic predicate call This is the trace event It is either call exit redo fail or exception dynamic This is an indication of the representation of the current goal s predi cate It is either dynamic indicating interpreted code or static indicating compiled code fact 3 _195168 This is the current goal This field is written using write_term 2 along with the value of the flag debug_write_term_options The question mark at the end of the output indicates that the system has stopped execution and is waiting for the user to input a debugging command As a consequence we know that either the goal predicate has a spypoint as it is in this example or this is a leashed event and we are tracing No question mark is shown when the debugger continues to execute the traced event without asking for a debugging command As an example of
104. ame arguments This predicate behaves as if it was defined as follows term_expansion TermIn Term0ut current_term_expansion Functor Goal Functor TermIn Term0ut call Goal Examples assert inconsistent_expander false true yes add_term_expansion inconsistent_expander yes false yes Errors None See also add_term_expansion 1 current_term_expansion 1 del_term_expansion 1 4 1 219 throw 1 Synopsis throw T Description This predicate searches for the nearest exception handler installed by catch 3 which can handle the argument T Control is then passed to this handler 202 CHAPTER 4 BUILT IN PREDICATES Examples catch throw foo E format Cought exception qn E Cought exception foo E foo yes Errors instantiation_error The argument T was not instantiated See also catch 3 4 1 220 true 0 Synopsis true Description The predicate which always succeeds Examples true yes Errors None See also fail 0 4 1 221 unget_byte 1 Synopsis unget_byte B 4 1 PREDICATES 203 Description Behaves as if it were defined as follows unget_byte Byte current_input S unget_byte S Byte Examples See unget_byte 2 Errors See unget_byte 2 See also current_input 1 unget_byte 2 4 1 222 unget_byte 2 Synopsis unget_byte S B Description Places a byte B into the binary str
105. amp debug flags ooa 8 2 5 6 Set trace amp debug flags 8 3 The Prolog Language 9 Bal e ae e i ie ee me Aes ee e ee Ep g 9 d ao e e E ek E R ee ee 17 iii iv CONTENTS 4 Built in Predicates 21 4 1 Predicates 424 2403 46 i408 HA RR eR EERE OS 21 A ee Ae ee Si we a 21 AD SO oe a A Ye ee Be ea Te R 22 4 1 3 absolute_file_name 2 23 4 14 absolute file name 3 ooe scu nob res eae u 23 4 1 5 add_file_search_path 2 26 4 1 6 add_generate_message 1 27 4 1 7 add_message_ho0k 1l o 28 Al add portray l cos socorro cts ad we m2 29 4 1 9 add_portray_message 1 31 4 1 10 add_query_class_ho0k 1l 32 4 1 1 add_query_input_hook 1 o0o o 33 4 1 12 add_query_map_ho0k 1l 35 4 1 13 add_term_expansion i 35 LL Spends ie bees Phoebe ada ds 37 A iy oe OS o e a ae E a SY EERE RGSS 37 d VAG arg 3 AE eo 38 4 1 17 Arithmetic comparison with evaluation 39 4 1 18 Arithmetic comparison without evaluation 40 ALLIED rca A a e ee ER e e 40 aa ask guera o ere ea ee i 41 ADO assert oona a a ek ee EE eae e 42 Adige asserta Leo ca ee rena koe raire Ee Se ODE S a 43 e125 asserta 1 2 kh eee e A AES e 44 AA 2A at end of str am O os of ASE LOL eR Bs 45 4 1 25 at_end_of_stream 1 45 LLO Edo ls 2 ec pias ira hr ee a 46 ie se e iy eb ae he ea a ke foe Ae a a 46 AI
106. an of a sample is already known In other cases sample_standard_deviation 2 should be used Examples sample_standard_deviation 1 1 1 1 D D 0 07 yes sample_standard_deviation 1 2 3 2 D D 1 0 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list 332 CHAPTER 13 THE STATISTICS LIBRARY Also as the argument M and the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_standard_deviation 2 13 1 25 sample_variance 2 Synopsis sample_variance L Result Description Result is the sample variance of the list of numbers L Examples sample_variance 1 1 1 V V 0 0 7 sample_variance 1 2 3 V 1 0 lt Il yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_variance 3 13 1 26 sample_variance 3 Synopsis sample_variance L M Result 13 1 PREDICATES 333 Description Result is the sample variance of the list of numbers L which has an arithmetic mean of M This predicate is provided for the cases where t
107. ansposes that graph and unifies P with the result in P representation Examples p_to_s_graph a b b c c d a c S s_to_p_trans S P S a b c b c c d d P b a c a c b d c yes Errors None See also s_to_p_graph 2 252 CHAPTER 7 THE GRAPHS LIBRARY 7 1 8 s_transpose 2 Synopsis s_transpose G1 7G2 Description This predicate takes a graph G1 in S representation transposes that graph and unifies G2 with the result in S representation Examples p_to_s_graph a b b c c d a c S s_transpose S S2 s_to_p_graph S2 Pt S a b c b c c d d S2 a b a c a b d c Pt b a c a c b d c yes Errors None See also s_to_p_trans 2 7 1 9 top_sort 2 Synopsis top_sort G L Description Succeeds if the topological sort of the graph G in S representation is the list of vertices L Examples p_to_s_graph a b b d c d d e S top_sort S Sorted S a b b d c d d e e 1 Sorted a b c d e yes 7 1 PREDICATES 253 Errors None See also None 7 1 10 vertices 2 Synopsis vertices G V Description This predicate takes a graph G in S representation and unifies V with a list of the vertices found in that graph Examples p_to_s_graph a b b c c d a c S vertices S V S a b c b c c d d V a b c d yes Errors None See also None 7 1
108. ap 4 Synopsis query_map Method Input Result Answer Description This predicate is used internally by ask_query 4 The argument Input is the output from a call to query_input 3 which is a list of character codes This is mapped to the argument Answer using a method indicated by Method The success of this mapping is indicated by unifying Result with either success or failure The argument Method is one of the following char Pairs Here Pairs should be a list of key pairs The keys are terms with lists of character codes as corresponding values This map method will search Pairs for the first character code say Code in Input that is either a newline Code 10 or non whitespace Code gt 32 The corresponding key is unified with Answer The arguments Answer and Input are unified Examples query_map char yes Yy no Nn yeah Answer Result Answer success Result yes yes query_map char yes Yy no Nn maybe Answer Result 172 CHAPTER 4 BUILT IN PREDICATES Answer failure Result _642464 yes Errors None See also ask_query 4 add_query_map_hook 1 key_pair 1 4 1 186 query_read_line 2 Synopsis query_read_line Stream Line Description This predicate reads a sequence of character codes from Stream and accu mulates these codes in Line Reading stops when an end of file code 1 or a newline code 10 is encountered Line includes a final ne
109. argument The argument must be an integer greater than or equal to zero lt lt E1 E2 Calculates the bit wise left shift of the arguments El is shifted left E2 bits Both arguments must be integers greater than or equal to zero E1 E2 Calculates the bit wise or of the arguments Both arguments must be integers greater than or equal to zero gt gt gt E1 E2 Calculates the bit wise right shift of the arguments El is shifted right E2 bits Both arguments must be integers greater than or equal to zero ceiling E Calculates the smallest integer that is not less than the argu ment cos E Calculates the cosine of the argument in radians This is an elemen tary function found in elementary_functions fasl exp E Calculates the value of natural antilogarithm of the argument This is an elementary function found in elementary_functions fasl xx E1 E2 Calculates the exponentiation of the arguments El is raised to the power of E2 This is an elementary function found in the file elementary_functions fasl If El is less than zero then E2 must be an integer If El is zero then E2 must be greater than or equal to zero factorial E Calculates the factorial of the argument The argument must be an integer greater than or equal to zero This is a special function found in special_functions fasl float E Converts the argument into a floating point number float_fractional_part E Calculates the fractional part of th
110. ars 3 Synopsis numbervars Term Start End Description The variables in Term are unified with terms of the form VAR C where C is a unique integer identifier for each such variable This identifier takes the form of a counter which has the initial value Start and a final value of End 1 4 1 PREDICATES 133 When the predicate write_term 3 is called with the option argument containing numbervars true and a argument which contains a term of the form VAR C where C is a positive integer then instead of VAR C a Prolog variable is written The name of this variable is unique for each individual C If C is less than 26 then the variable name is the single upper case letter identified with the C element of the English alphabet The letter A is considered to be the zeroth element of the alphabet Example writeq VAR 0 writeq VAR 25 AZ yes If C is greater than 25 then the variable name takes the form of a letter followed by a sequence of digits The letter is calculated to be the nt element of the English alphabet where n is C modulo 26 and the sequence of digits is the decimal representation of the integer division of C and 26 Example writeq VAR 26 writeq VAR 52 nl A1A2 yes Examples Term foo X Y Z numbervars Term 0 Count writeq Term nl foo A B C Term foo VAR 0 VAR 1 VAR 2 X VARCO Y VAR 1 Z
111. at See the flag number_output_base for the base representation scientific The text written comprises of a single digit integral part a radix point a fractional part the character e then an exponent part Example 1 23e4 4 3 8 floating_point_output_precision Description The value of this flag is the number of base digits after the radix point that are written by write_term 3 A value of N means generate all digits A value of N means generate N digits Default Value 6 Possible Values Any integer less than or equal to 0 4 3 9 floating_point_precision Description The value of this flag is the number of bits of precision used for the fraction part of a floating point number See eval 2 Default Value 64 230 CHAPTER 4 BUILT IN PREDICATES Possible Values Any integer greater than 0 4 3 10 integer_rounding function Description This is a flag specified by the ISO Prolog standard to show the direction in which integer division rounds Default Value toward_zero Possible Values This is a constant flag and cannot be changed from the default 4 3 11 max_arity Description The value of this flag is the maximum arity of any predicate or compound term Default Value 255 Possible Values This is a constant flag and cannot be changed from the default 4 3 12 modulo Description This is a flag specified by the ISO IEC 10967 standard to be false since the flag bounded is false Default Val
112. at atom A var B is true and A is the name of a variable that appears only once in the term and B is the corresponding variable variables V Vis unified with a list of all the variables read variable_names V Vis unified with a list of A B pairs such that atom A var B is true and A is the name of a variable that appears in the term and B is the corresponding variable 4 1 PREDICATES 175 Examples read_term T position P singletons S variables V variable_names N foo A B B T foo _565216 566080 566080 P stream_position 0 1 77 0 S A _565216 V _565216 _566080 N A _565216 B _566080 yes Errors domain_error read_option Option The element Option of the list O was not a valid read option domain_error stream_or_alias S The argument S was not a valid stream term or alias existence_error stream S The argument S does not refer to an open stream instantiation_error Fither one of the arguments T or 0 was not instan tiated or O was a list where one of the elements was a variable lexical_error end_of_file The input stream ended in the middle of a token lexical_error strange_character Char The character code Char was found inside a token permission_error input binary_stream S The stream S was not a text stream permission_error input past_end_of_stream S An attempt was made to read past the end of the stream S permission_error input
113. ation error Goal in error variable _628736 This exception was thrown because argument number 1 was not sufficiently instantiated Msg error instantiation_error instantiation_error variable _628736 1 lt Il _628736 ERROR n1 Error class instantiation error nl EA Il 4 1 PREDICATES 129 Goal in error q variable _628736 n1 This exception was thrown because argument number q was not sufficiently instantiated 1 n1 Lines ERROR Error class instantiation error Goal in error q variable _628736 This exception was thrown because argument number q was not sufficiently instantiated 1 yes Errors None See also add_generate_message 1 generate_message_lines 3 4 1 130 min 3 Synopsis min A B C Description Succeeds if C is the minimum of A and B This predicate behaves as if it were defined as min A B C A lt B C A min _ B B Examples min 1 2 Min Min 1 yes min 2 1 Min Min 1 yes 130 CHAPTER 4 BUILT IN PREDICATES Errors Since A and B are evaluated errors may be thrown by eval 2 See also None 4 1 131 name 2 Synopsis name A C name A C Description Succeeds if the argument C is a list of character codes which represent the argument A A can be a number or a symbol Examples name A foo A foo yes name 99 C C
114. aused whilst the file named in the argument of the directive is loaded should it need to be Example ensure_loaded runtime statistics 2 4 4 include 1 This has the effect of including the contents of the argument file into the current file The use of an include directive should have the same effect as if the user had manually included the contents of the argument file into the file being processed However any errors or warnings generated in the included file will be reported with the correct file name and position Example include home prolog code useful_operator_definitions 2 4 5 initialization 1 When the current load has been completed the initialization directive s ar gument is called A file can have several such directives However you should note that there is no guarantee given for the order in which the arguments of the directives are called Example initialization print Loaded Should the goal fail then a warning message is printed As an example consider the following directive initialization fail It generates the following message The following goal failed fail 2 4 6 multifile 1 The argument to this directive is a predicate indicator a sequence of predi cate indicators separated by 2 or a list of predicate indicators This directive informs the system that the procedures indicated by the predi cate indicators may be defined in more than one file T
115. bers L Examples sample_geometric_mean 2 8 M M 4 0 yes Errors domain_error non_empty_list The argument L was the empty list 0 instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also None 13 1 PREDICATES 323 13 1 15 sample_harmonic_mean 2 Synopsis sample_harmonic_mean L M Description This predicates calculates the harmonic mean M of a list of numbers L Examples sample_harmonic_mean 1 2 4 M M 1 714286 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also None 13 1 16 sample_interquartile_range 2 Synopsis sample_interquartile_range L Result Description Result is the sample interquartile range of the list of numbers L This pred icate behaves as if it were defined as sample_interquartile_range L Result sample_quantile L 0 75 SeventyFive sample_quantile L 0 25 TwentyFive Result is SeventyFive TwentyFive 324 CHAPTER 13 THE STATISTICS LIBRARY Examples sample_interquartile_range 1 2 3 4 5 6 7 8 R R 4 0 y
116. cally consulted by the query test compile_file test pl test fasl Compiling test pl Finished Writing test fasl Done yes test yes foo 1 yes bar 2 yes procedure_property foo 1 Prop Prop dynamic yes procedure_property bar 1 Prop Prop static yes Errors The compiler calls open 3 and read_term 3 both of which may throw errors 15 1 PREDICATES 359 See also None 15 1 2 compile_procedure 1 Synopsis compile_procedure PI Description Compiles the dynamic procedure indicated by the predicate indicator PI Examples assert foo X member X 1 2 3 X _548432 yes foo 2 yes procedure_property foo 1 Prop Prop dynamic yes compile_procedure foo 1 yes foo 2 yes procedure_property foo 1 Prop Prop static yes Errors instantiation_error The argument PI was not instantiated type_error dynamic_procedure PI The argument PI did not indicate a dynamic procedure type_error predicate_indicator PI The argument PI was not a pred icate indicator See also None 360 CHAPTER 15 COMPILING Bibliography BBPT81 D L Bowen L Byrd L M Pereira F C N Pereira and Byr80 DM93 D H D Warren PROLOG on the DECSystem 10 user s man ual Technical report Department of Artificial Intelligence Uni
117. d the procedure specified by the predicate indicator F 4 Examples current_query_map_hook F no add_query_map_hook foo yes current_query_map_hook F F foo yes del_query_map_hook foo yes 78 CHAPTER 4 BUILT IN PREDICATES current_query_map_hook F no Errors None See also add_query_map_hook 1 del_query_map_hook 1 4 1 70 current_term_expansion 1 Synopsis current_term_expansion A Description Succeeds if the predicate identified by the predicate indicator A 2 has been registered as a term expansion hook Examples add_term_expansion one yes add_term_expansion two yes findall X current_term_expansion X L X _522304 L one two yes Errors None See also add_term_expansion 1 del_term_expansion 1 term_expansion 2 4 1 71 Cut 0 Synopsis 4 1 PREDICATES 79 Description Removes all choice points created since the currently executing predicate was called The predicates call 1 once 1 and 1 block the cut that is to say the effect of any cut in a term given as an argument to these predicates is limited to any choice points created by that term The predicate gt 2 will limit the scope of any cuts in its first argument to just that argument that is to say that these cuts are also blocked Other predicates such as 2 979 9 2 and 2 do not block cuts Examples
118. d Bee ad Oe ed Hee ole 260 SLO AIRI wk death deka a he eee ee et bebo a 260 SL OEMIISE IE nu ha fe ee ie a bee eG bla x 261 SLIL PEA e e fae Rive Ae a eR a OR 2 262 PLE DUE ir A RES RS 262 CONTENTS 9 The 9 1 10 The 10 1 11 The TEI S 1 13 renove QUps 2 oa re de hw RA we RE e b a lIl Feya e yoro aia ee de Se me a a ee eo 8 1 15 same_length 2 oc ooe ca ee a a 8 1 10 pelegt f ooa nans a aae a a a a 8 1 17 s6lecpehk d ose amp bw ar ee ae eh es LIS s lect 3 ooo as copa ee ee Re ER a Cul lO BELeCEChK S 2s vs a eG sal woke ee ee el Bherper ISEI yed 45 a ack PhS DR we Ss A 36 en ek ee Roe Be we Wa he A we dae dw A 2 oo ek a eS ele Ee ee ee a L23 SUBE a i eae ee eee A a Ll BUSES Lo ci e eee a Re he eb ws ordset library Pedone ul e aoe ae Bie wb a wd ee woe O11 list to ord sets ici a 9 1 2 ord_all_nonempty_subsets 2 Cie ord all EUDEGESID curo a he ee 9 1 4 ord_all_subsets 3 9 1 5 ord_all_unordered_pairs 3 O68 Ord disjoint 2 cos corras eb be ew BOS HS OLI ord BaS ioare ce Res wo el ee eee ee 91 8 Grd inteFsect 2s 6 ac bb A ee e kerta 9 1 9 ard anters ct S ici a 91 10 ord powerset 2 so oeo es as ses ma e OL ord product 3 i nc ae hae hae ee the ee bee eS 91 12 ordssebeg 2 o ssc he ere ee eb eS 9 1 13 ord subeet 2 ociosas kh ee Eee a See 9 1 14 ord _subtract 3 oscense y a 0 1 15 E o sed ma eee k h aeea bee ds 0 1 10 ord union 3 asror es printtree library Ma
119. d input character permission_error input past_end_of_stream S Tried to read past the end of the stream permission_error input stream S There is a lack of permission to read from stream S permission_error input binary_stream S The argument S refers to a binary stream 114 CHAPTER 4 BUILT IN PREDICATES existence_error stream S The stream S does not exist domain_error stream_or_alias S The argument S is not a valid stream term or stream alias See also unget_char 2 4 1 108 get_code 1 Synopsis get_code C Description Behaves as if it were defined as follows get_code Code current_input S get_code S Code Examples See get_code 2 Errors See get_code 2 See also current_input 1 get_code 2 4 1 109 get_code 2 Synopsis get_code S C Description Reads a character code C from the text stream S 4 1 PREDICATES 115 Examples test_get_code open test_file txt read Stream get_code Stream 64 get_code Stream 65 get_code Stream 66 get_code Stream 67 skip_to_end_of_text_file Stream close Stream Errors instantiation_error The argument S was not instantiated representation_error in_character_code C The argument C was in stantiated but not a valid input character code permission_error input past_end_of_stream S Tried to read past the end of the stream permission_error input stream S There is a lack of permission to r
120. d oe eS Kew ce ee ee PR ES 233 SLI assoeztolist 2 he cee ee ee ee a 233 Dele get assot 3 orp ele eb a Ae aoe 234 Uli MAPAS e phe ae A da 235 Ola pubvassocy4 o pate eee wee eM ee ba ee 236 bup library 237 Predicates sos os eee ee ee ey be ee we 241 6 1 1 Dbup compile 2 2 vse kee eee hee Le oS 241 6 12 Dup compile jes ok ye ee Ey e GD hws 241 6 1 3 MPAA OE ales RAPE ew RE EES 242 Gils BOPA ob ce Shae PE RRE SE SRS ES EH 243 Gl Pup vi Bee ca he eee eee ee eR D Se 244 6 1 6 A c cese be ec ee eee bw ws 245 graphs library 247 Predicates 5 oe py eae bw Sb ah be ey ewe ws 247 Ask GOMBOEE 2 ed Bee id AG ee dS 247 Tell penro os Loe Ale ee OA ae e Be eS 248 LO PAoL e graph 2 o reci ee eee Re DR 8 249 GAA Plpranspose 2 ne eh ee woh we oY 249 lO B_UBMBELES o rios p ee bee Sea Rae Eb ee we 250 GLO SOPAS o bn cb ee ee ey PR ee OS HO 250 Tela BOPA on ee k ea oh ea 2s 251 TLS g transpos 2 2 ck keke wR E RDA Re LES OS 252 GRI o es ook BS Ads Pe Pa ee Se 252 AAD Werbices 2 ro Shas PR Se A ee 253 Voll warsball 2 occiso boas ee eS RE ewe HO 253 lists library 255 Predicates wo a ek oir a or a a a ae amp A 255 amp LIL wormespond 4 ost ecap oa nb eee Ee baw 255 Sle ABUECSIS cupo bk heed heed eA EGE 256 Glo WaAsSt 2 64 ii 428 he Bee OE RA ORE OE 256 SL MEMOS e ewe BEE ee nee ee eee es 257 S15 TMemberid car ee A ke ne ha e 258 S16 Timembers 3 cocos o bee eR ER sde 258 Bly eRe 2 ek ie ee BAe Be ea p e oe Bae a 259 E AUO Gs 2 6 ee eG e
121. d the ISO IEC 10967 stan dards to show whether or not bounded integer arithmetic is implemented The flag value of false indicates that we have arbitrary precision integers that is to say the maximum and minimum integers are not bounded by some predefined constants Default Value false 4 3 FLAGS 227 Possible Values This is a constant flag and cannot be changed from the default 4 3 2 char_conversion Description A switch which enables or disables the conversion of characters in unquoted terms read by read_term 3 Characters are converted according to the char acter conversion table which is described by current_char_conversion 2 Default Value on Possible Values on Unquoted terms are subject to character conversion off Unquoted terms are not subject to character conversion 4 3 3 char_escapes Description A switch which controls the behaviour of read_term 3 when it encounters the backslash character ASCII 92 X in a symbol When enabled the next character is interpreted as an escape character Default Value on Possible Values on Enable the interpretation of as an escape character off Disable the interpretation of as an escape character 4 3 4 collapse_multiple_minuses Description A switch which controls the behaviour of read_term 3 when it encounters any atoms which have names which comprise only of three or more minus characters When set to on any such atom is report
122. d_t_test 5 14 Debug 14 1 A Simplified Tracer 14 2 The Debugger 14 2 1 Starting the debugger 14 2 2 Trace output 14 2 3 Debugging Commands 14 3 Debug Predicates 14 3 1 add_spypoint 1 14 3 2 debug 0 gt o ra ecas 14 3 3 debugging O 14 34 Leash 1 co 14 3 5 nodebug O 1436 Hespy l ess cossu 14 3 7 nospyal1 0 14 3 8 notra e Q o oso 14 3 9 remove_spypoint 1 LEN ea we ees 14 3 11trace 0 14 4 Debug Flags TAAT debt g os Soe ed 14 4 2 debug_write_term_options MAS trace oo fs ane 15 Compiling 15 1 Predicates 15 1 1 compile_file 2 15 1 2 compile_procedure 1 xiii 323 323 324 325 326 326 327 329 330 331 332 332 333 334 335 336 339 339 341 342 343 344 346 346 347 348 348 349 350 350 351 352 352 353 354 354 354 355 xlv CONTENTS Chapter 1 Introduction 1 1 About The Barry s Prolog Manual describes a mostly ISO compliant Prolog system which consists of an interpreter a compiler a debugger and a collection of useful predicates This manual tells you how to configure and start the system and provides a reference to all the library predicates This manual is intended for any user of the system It assumes you are familiar with Prolog programming 1 2 Notation 1 2 1 Typeface Throughout the manual examples of Prolog code or interactions with the Prolog system are indicated b
123. des Input InputRest Description Succeeds if Codes is the difference between the lists Input and InputRest and the last element of Codes is a double quote character code ASCII 34 Two adjacent double quotes in the difference list correspond to one double quote in Codes This predicate is used to parse the remainder of string literals when the leading double quote has already been consumed This predicate behaves as if it were defined as follows chars_to_string 34 Cs gt 34 34 chars_to_string Cs chars_to_string gt 34 chars_to_string C Cs gt C chars_to_string Cs Examples yes chars_to_string foo A B A 102 111 111 34 _554928 B _554928 yes chars_to_string Codes foo Rest Codes 102 111 111 Rest yes Errors None See also None 12 1 5 chars_to_words 2 Synopsis chars_to_words Codes Words 12 1 PREDICATES 297 Description Behaves as if it were defined as follows chars_to_words Codes Words chars_to_words Words Codes Examples See chars_to_words 3 Errors instantiation_error Codes must be ground As each element of Codes is evaluated errors may be thrown by eval 2 See also chars_to_words 3 12 1 6 chars_to_words 3 Synopsis chars_to_words Words Codes CodesRest Description The character codes in the list Codes are scanned and transformed into the list of terms Words Th
124. e aposts Rest yes chars_to_words Words 123 foo Rest Words integer 123 atom foo Rest yes Errors If Codes is not ground then an endless loop will be entered As each element of MixedCaseCodes is evaluated errors may be thrown by eval 2 See also None 12 1 7 is_digit 1 Synopsis is_digit Code Description Succeeds if Code represents an decimal digit Examples is_digit 0 3 yes 12 1 PREDICATES 299 Errors As Code is evaluated errors may be thrown by eval 2 See also None 12 1 8 is_endfile 1 Synopsis is_endfile Code Description Succeeds if Code is the end of file character code which is 1 Examples is_endfile Code Code 1 yes Errors None See also None 12 1 9 is_layout 1 Synopsis is_layout Code Description Succeeds if Code represents an unprintable layout character which is any code value less than or equal to 32 Examples is_layout 32 yes 300 CHAPTER 12 THE READSENT LIBRARY Errors As Code is evaluated errors may be thrown by eval 2 See also None 12 1 10 is_letter 1 Synopsis is_letter Code Description Succeeds if Code represents an English language letter of either upper or lower case Examples is_letter 0 a yes is_letter 0 B yes Errors As Code is evaluated errors may be thrown by eval 2 See also None
125. e 307 12 4a red motile ke eae es ae ee Ae A 308 12 ELO Grim blanks 2 oo bee oh renh ine eo we DE 308 13 The statistics library 311 tool Predicates oa on5 4 ba ee ee Ge Gee a 311 ESE ERE UA TRES e we eee ee ew 311 13 1 2 chi squared pat S ocios a 312 13 1 3 chi_squared_quantile 3 313 IODA Ple es ee ee Ea Eee a 314 WE Sopa ee a ek Noe ee Ra Ree be ek Bae U 314 13 1 6 Poquantile 4 6 eee eee eee eee eS 315 13 1 7 normalcdi door be E OES Ee Oe we 316 3 1 8 mormal pdt 4 vc aa a eae 317 13 1 9 normal_quantile 4 318 13 1 10 population_mean_confidence_interval 4 318 13 1 11 sample_absolute_deviation 3 319 13 1 12sample_arithmetic_mean 2 320 13 1 13 sample_coefficient_of_variation 2 321 13 1 14sample_geometric_mean 2 322 CONTENTS 13 1 15sample_harmonic_mean 2 13 1 16 sample_interquartile_range 2 13 1 17 sample_mean_absolute_deviation 2 13 1 18sample_median 2 13 1 19 sample_median_absolute_deviation 2 13 1 20sample_quantile 3 13 1 21 sample_quantile 7 13 1 22 sample_semi_interquartile_range 2 13 1 23 sample_standard_deviation 2 13 1 24sample_standard_deviation 3 13 1 25sample_variance 2 13 1 26sample_variance 3 13 1 27 students_t_cdf 3 13 1 28 students_t_pdf 3 18 129 students tuquantile S oci en be ee eS 13 1 30unpaire
126. e Values on If the debugger is loaded then it is engaged and it will start operation off Disengage the debugger 14 4 2 debug_write_term_options Description A list of options used to configure the output of the current goal in trace output Default Value quoted true numbervars true Possible Values Any possible legal option list that can be passed to write_term 3 You might want to avoid the option portray true as this could lead to the debugger calling dynamic predicates which could lead to a recursive call to the debugger 14 4 DEBUG FLAGS 14 4 3 trace Description A switch to control the debugger s trace output generation Default Value off Possible Values on Turn on debugger trace outputs off Turn off debugger trace outputs 355 356 CHAPTER 14 DEBUG Chapter 15 Compiling The compiler is used to speed up the execution of Prolog procedures Com piled static procedures cannot be analysed with the debugger nor can existing compiled procedures be augmented by consulting or replaced by reconsulting The user who wishes to compile has two options Dynamic procedures in the clause store can be individually compiled In this case they are removed from the clause store and placed into the code section They then cease to be dynamic and become static instead This method of compilation is useful during program devel opment when the user is not entirely confident that a procedure is workin
127. e also functor 3 4 1 20 ask_query 4 Synopsis ask_query Class Query Help Answer Description Prompts the user for input reads input and possibly provides help upon input failure The body of ask_query 4 is essentially the following query_class Class Prompt InputMethod MapMethod FailureMode generate_message_lines HelpLines Help generate_message_lines QueryLines Query message_hook query Query QueryLines query_input InputMethod Prompt Input query_map MapMethod Input Result Answer Should Result be success then ask_query 4 has finished Otherwise be haviour depends upon FailureMode where the possible values are none Control loops back to query_input 3 42 CHAPTER 4 BUILT IN PREDICATES query Control loops back to message_hook 3 redisplaying the query text help The help text is displayed with message_hook help Help HelpLines and control loops back to query_input 3 help_query The help text is displayed with message_hook help Help HelpLines then control loops back to message_hook 3 redisplaying the query text Examples ask_query query J Input term 1 2 3 Input term 1 2 3 yes ask_query yes_or_no Reboot nl Please answer yes or no nl Answer Reboot y or n m Please answer yes or no Reboot y or n n Answer no yes Errors None See also None 4 1 21 assert 1 Synopsis
128. e association list NewAssoc is the result of inserting the pair Key Value into the association list OldAssoc Should Key already be associated with a value in OldAssoc the insertion operation updates the existing association Examples put_assoc key t value Assoc0 get_ assoc key Assoc0O Value0 put_assoc key AssocO new_value Associ get_ AssocO Valued Associ Valuei yes Errors None See also assoc key Associ Valuel t key value t t value t key new_value t t new_value get_assoc 3 Chapter 6 The bup library To use the predicates in this library you will need to load the bup fas1 file One way to do this is with the following call ensure_loaded runtime bup This library implements a parser generator as described in the paper MITH 83 The main differences between parsers generated by BUP and those generated by a DCG are e BUP creates a bottom up parser which can process a left recursive grammar A DCG parser is of the top down type and cannot process these grammars e BUP can split input processing into grammar rule application and dic tionary look up This permits the independent processing of grammar terminals For example a natural language parser may make use of a dictionary too large to store in the grammar itself so the system could store the dictionary in a file and search this file for words when needed e BUP can be configured to create a
129. e floating point argument float_integer_part E Calculates the integer part of the floating point argument The result is a floating point number E1 E2 Calculates the floating point division of El by E2 E2 must not evaluate to zero gt E1 E2 Calculates the integer division of E1 by E2 Both arguments must be integers E2 must not evaluate to zero 94 CHAPTER 4 BUILT IN PREDICATES div E1 E2 Calculates the floored division of E1 by E2 Both arguments must be integers E2 must not evaluate to zero floor E Calculates the largest integer that is not greater than the argu ment gamma E Calculates the gamma generalised factorial of the argument This is a special function found in special_functions fasl In E Calculates the natural logarithm of the argument This is an elemen tary function found in elementary_functions fasl log E Calculates the base 10 logarithm of the argument This is an ele mentary function found in elementary_functions fasl mod E1 E2 Calculates El modulo E2 Both arguments must be integers E2 must not evaluate to zero E1 E2 Calculates the multiplication of the two arguments rem E1 E2 Calculates E1 remainder E2 Both arguments must be integers E2 must not evaluate to zero round E Calculates the nearest integer to the argument sign E The result is the sign of the argument gt E Calculates the unary minus of the argument i e the sign of the argument is rev
130. e is generated and if any generate message hooks exist they are called Output is sent to the stream user_error The following are the valid severity values for S banner The message has no prefix error The message is prefixed with help The message has no prefix informational The message is prefixed with none The message has no prefix query The message has no prefix 4 1 PREDICATES 157 silent The message is not output warning The message is prefixed with Examples print_message banner I am a banner I am a banner yes print_message error I am an error I am an error yes print_message help I am help I am help yes print_message informational I am informational I am informational yes print_message none I am none I am none yes print_message query I am a query I am a query yes print_message silent I am silent yes print_message warning I am a warning I am a warning yes Errors None See also add_portray_message 1 add_generate_message 1 4 1 166 print_message_lines 3 Synopsis print_message_lines Stream Severity Lines 158 CHAPTER 4 BUILT IN PREDICATES Description This procedure is used internally by print_message 2 to print the message Lines with Severity on Stream This procedure should be used to generate formatted output in a message h
131. e option cache_goals on is given The parser then uses this predicate as a cache of pairs of grammar non terminals and input sequences Such a pair indicates a failure to parse the input sequence as being of the type described by the non terminal This cache is used to avoid recomputation in subsequent parses You may wish to use retractall 1 to remove this predicate and flush the cache Examples Here we assume that we have compiled the file grammar bup defined above with the option cache_goals on bup_goal s A the cat chases the rat no listing bup_fail_goal 2 bup_fail_goal noun rat bup_fail_goal np the rat bup_fail_goal vp chases the rat bup_fail_goal s the cat chases the rat yes Errors None See also bup_compile 3 retractal1 1 6 1 4 bup_goal 4 Synopsis bup_goal NonTerminal ArgumentList Input Remainder Description Succeeds if Input and Remainder form a difference list and the actual differ ence can be parsed as a NonTerminal with grammar arguments ArgumentList Examples Here we assume we have loaded the grammar contained in grammar pl which was defined above 244 CHAPTER 6 THE BUP LIBRARY bup_goal np Args the cat chases the mouse X Args np d the n cat X chases the mouse yes Errors None See also bup_compile 3 6 1 5 bup_wf_dict 4 Synopsis bup_wf_dict NonT
132. e remainder of Codes which could not be scanned is unified with CodesRest i e Codes and CodesRest form a difference list Each term element of the list Words is one of the following apost Corresponds to an apostrophe ASCII 39 which was not followed by an s or S ASCII 83 or 115 aposts Corresponds to an apostrophe ASCII 39 which was followed by an s or S ASCII 83 or 115 atom A Corresponds to a sequence of upper and or lower case letters The argument A is the atom whose name is represented by this sequence where all upper case letters have been shifted to lower case letters integer I Corresponds to a sequence of decimal digits The argument I is the integer representation of these digits 298 CHAPTER 12 THE READSENT LIBRARY string S Corresponds to a double quote ASCII 34 followed by a sequence of character codes terminated by a double quote Any adjacent occur rences of the double quote character code which are seen when forming the sequence lead to a single double quote being added to the sequence and the formation of the sequence continues Atom The single character atom Atom corresponds to a character code which has a value greater than 32 and which is neither an alphabetic character code a decimal digit character code an apostrophe ASCII 39 nor a double quote ASCII 34 Examples chars_to_words Words quote quote s Rest Words apost atom quote apost atom quot
133. ead from stream S permission_error input binary_stream S The argument S refers to a binary stream existence_error stream S The stream S does not exist domain_error stream_or_alias S The argument S is not a valid stream term or stream alias See also unget_code 2 4 1 110 ground 1 Synopsis ground T Description Succeeds if T is a ground term 116 Examples ground X no ground x yes ground foo x yes Errors None See also None 4 1 111 halt 0 Synopsis halt Description CHAPTER 4 BUILT IN PREDICATES Halts execution The operating system is given a exit status code equivalent to the call exit EXIT_SUCCESS in the C programming language Examples halt Errors None See also halt 1 4 1 112 halt 1 Synopsis halt N 4 1 PREDICATES 117 Description Halts execution with exit code N The predicate fails if N is not an integer that fits into a target machine word The operating system is given a exit status code equivalent to the call exit N in the C programming language Examples halt 99 Errors instantiation_error N must be ground type_error integer N N must be of type integer See also halt 0 4 1 113 If gt gt 2 Synopsis Ti gt T2 T1 gt T2 T3 Description The case T1 gt T2 is equivalent to T1 gt T2 fail The case Ti gt T2 T3 is equivalent to call T1
134. eam reposition true stream_position_byte_count Pos0 1 stream_position_line_count Pos0 2 stream_position_character_count Pos0 3 186 CHAPTER 4 BUILT IN PREDICATES stream_position_line_position Pos0 4 set_stream_position OutStream Pos0 stream_property OutStream position Pos1 stream_position_byte_count Pos1 1 stream_position_line_count Pos1 2 stream_position_character_count Pos1 3 stream_position_line_position Pos1 4 close OutStream DutStream stream 3 PosO stream_position 1 2 3 4 Posi stream_position 1 2 3 4 yes Errors domain_error stream_position Position The argument Position was not a valid stream position domain_error stream_or_alias Stream The argument Stream was not a valid stream term or alias atom existence_error stream Stream The argument Stream identified a nonex istent stream instantiation_error One of the arguments Stream or Property was not instantiated permission_error reposition stream Stream There was no permis sion to reposition the stream Strean See also seek 4 stream_position_byte_count 2 stream_position_character_count 2 stream_position_line_count 2 stream_position_line_position 2 4 1 201 setof 3 Synopsis setof Template Goal Set Description Similar to bagof 3 but whereas that predicate computes a multiset this predicate computes a sorted set Thus setof 3 behaves as if it had the following definition 4 1
135. eam S so that it will be the next byte read from that stream Examples test_unget_byte open test_file bin read Stream type binary unget_byte Stream 16 11 get_byte Stream 16 11 close Stream Errors domain_error stream_or_alias S The argument Sis not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error The argument S was not instantiated 204 CHAPTER 4 BUILT IN PREDICATES permission_error input stream S There is a lack of permission to read from stream S permission_error input text_stream S The argument S refers to a text stream representation_error byte The argument B was instantiated but not a valid byte type_error integer B The argument B was instantiated but not a valid integer See also byte 1 integer 1 4 1 223 unget_char 1 Synopsis unget _char C Description Behaves as if it were defined as follows unget_char Char current_input S unget_char S Char Examples See unget_char 2 Errors See unget_char 2 See also current_input 1 unget_char 2 4 1 224 unget_char 2 Synopsis unget_char S C 4 1 PREDICATES 205 Description Places a character C into the text stream S so that it will be the next character read from that stream Examples test_unget_char open test_file txt read Stream unget_char Stream d get_char Stream d close Stream Err
136. ed as 228 CHAPTER 4 BUILT IN PREDICATES Default Value off Possible Values on Any atom whose name comprises only of three or more minus characters is read as off No special handling of atom names is performed 4 3 5 discontiguous_clauses_warnings Description A switch which controls the behaviour of consult 1 reconsult 1 and compile_file 2 when it encounters any procedure where the clauses are not all adjacent to one another Default Value on Possible Values on Print a warning message when a discontiguous clause is detected off No warnings are printed 4 3 6 double_quotes Description The value of this flag determines what happens when read_term 3 encoun ters a double quoted sequence of characters Default Value codes Possible Values atom The sequence of characters is to be interpreted as an atom name chars The sequence of characters is to be interpreted as a list of one char acter atoms codes The sequence of characters is to be interpreted as a list of character codes 4 3 FLAGS 229 4 3 7 floating_point_output_format Description The value of this flag determines the format used to write floating point numbers with write_term 3 Default Value decimal Possible Values decimal The text written comprises of a integral part and a fractional part separated by a radix point Example 12 34 Here decimal does not mean base 10 representation it just means not scientific form
137. ee also add_generate_message 1 current_generate_message 1 4 1 75 del_message_hook 1 Synopsis del_message_hook A Description Deregisters a message hook registered with add_message_hook 1 This pred icate always succeeds 82 CHAPTER 4 BUILT IN PREDICATES Examples current_message_hook F no add_message_hook foo yes current_message_hook F F foo yes del_message_hook foo yes current_message_hook F no Errors None See also add_message_hook 1 current_message_hook 1 4 1 76 del_portray 1 Synopsis del_portray A Description Deregisters a portray hook registered with add_portray 1 This predicate always succeeds Examples current_portray F no add _portray foo yes current_portray F F foo yes del_portray foo yes 4 1 PREDICATES 83 current_portray F no Errors None See also add_portray 1 current_portray 1 4 1 77 del_portray_message 1 Synopsis del_portray_message A Description Deregisters a portray message hook registered with add_portray_message 1 This predicate always succeeds Examples current_portray_message F no add_portray_message foo yes current_portray_message F F foo yes del_portray_message foo yes current_portray_message foo no Errors None See also add_portray_message 1
138. ee also nonvar 1 4 1 232 well_formed_body_term 1 Synopsis well_formed_body_term T 4 1 PREDICATES 211 Description Succeeds if T is a well formed body term This collection of well formed body terms is the smallest one satisfying i all variables are well formed body terms ii all predications where the principle functor is not one of 2 2 or gt gt 2 are well formed body terms iii if T1 and T2 are well formed body terms then so are e the conjunction of T1 and T2 T1 T2 and e the disjunction of T1 and T2 T1 T2 and e the implication of T1 and T2 T1 gt T2 Examples well_formed_body_term X X _525344 yes well_formed_body_term a b yes well_formed_body_term a b yes well_formed_body_term a gt b yes well_formed_body_term 99 no Errors None See also predication 1 var 1 4 1 233 write 1 Synopsis write T 212 CHAPTER 4 BUILT IN PREDICATES Description Behaves as if it were defined as follows write Term current_output S write S Term Examples See write 2 Errors See write 2 See also current_output 1 write 2 4 1 234 write 2 Synopsis write S T Description Behaves as if it were defined as follows write S Term write_term S Term numbervars true Examples See write_term 2 Errors See write_term 2 See also write_term 2 4 1 235
139. ent_portray 1 73 current_portray_message 1 74 current_predicate 1 74 current_prolog_flag 2 75 current _query_class_hook 1 76 current_query_input_hook 1 76 current_query_map_hook 1 77 current_term_expansion 1 78 debug 0 8 347 debugging 0 348 del 3 79 del_file_search_path 2 80 del_generate_message 1 81 del_message_hook 1 81 del_portray 1 82 del_portray_message 1 83 del_query_class_hook 1 84 del_query_input_hook 1 84 del_query_map_hook 1 85 INDEX del_term_expansion 1 86 delete 3 256 delete_al1 3 86 delete_all_equal_terms 3 87 delete_deterministically 3 88 display 1 89 display 2 89 ensure_loaded 1 90 equal 2 40 eval 2 91 expand_term 2 99 f_cdf 4 314 f_pdf 4 314 f_quantile 4 315 fail 0 100 file_search_path 2 100 findall 3 101 float 1 102 flush_output 0 103 flush_output 1 103 format 2 104 format 3 105 functor 3 108 generate_message_line 3 109 generate_message_lines 3 110 get_assoc 3 234 get_byte 1 111 get_byte 2 111 get_char 1 112 get_char 2 113 get_code 1 114 get_code 2 114 greater_than 2 40 greater_than_equal 2 40 ground 1 115 halt 0 8 116 halt 1 116 in_byte 1 118 in_character 1 118 in_character_code 1 119 infix_op_specifier 1 120 integer 1 120 io_mode 1 121 is 2 121 is_digit 1 298 is_endfile 1 299 is_layout 1 299 is_letter 1 300 is_lower 1 300 is_newline 1 301 is_paren 2 301 is_period 1 302 is_punct 1 302 is_upper 1 303
140. er Code put_code Code fail nl Errors None See also prolog_lexical_digit 1 prolog_lexical_symbol 1 prolog_lexical_upper_case_letter 1 prolog_lexical_ws 1 4 1 172 prolog_lexical_symbol 1 Synopsis prolog_lexical_symbol Code 162 CHAPTER 4 BUILT IN PREDICATES Description Succeeds if the character code Code represents a symbol non alphabetical character can be used in a Prolog atom name Examples prolog_lexical_symbol 0 yes prolog_lexical_symbol p no If your terminal can display the Unicode mathematical operators and arrows then you can try the following between 0 16 22ff Code prolog_lexical_symbol Code put_code Code fail nl Errors None See also prolog_lexical_digit 1 prolog_lexical_lower_case_letter 1 prolog_lexical_upper_case_letter 1 prolog_lexical_ws 1 4 1 173 prolog_lexical_upper_case_letter 1 Synopsis prolog_lexical_upper_case_letter Code Description Succeeds if the character code Code represents an alphabetical character that can be used to start a Prolog variable name Examples prolog_lexical_upper_case_letter 0 P yes prolog_lexical_upper_case_letter 0 p no If your terminal can display the Latin 1 codepage characters you can try the following 4 1 PREDICATES 163 between 0 16 22ff Code prolog_lexical_upper_case_letter Code put_code Code fail nl Errors None See als
141. ere in radix 16 hexadecimal the next two were radix 2 binary and the last two were in radix 8 octal The prefixes Ob 00 and Ox are defined by the ISO standard The numeri cal prefixes predate the ISO standard and more flexible as you can provide a numerical prefix between 2 and 36 inclusive Note that floating point numbers in radix 15 or higher that contain the radix digits e or E will not be interpreted correctly as e and E will be taken as the first character of the exponent part For ease of reading the underscore is ignored in numbers for example one million in decimal can be input as 1_000_000 3 1 SYNTAX 13 Compounds A compound term is a symbol an atom immediately followed by a set of terms within parenthesis Multiple terms within the parenthesis are sepa rated by commas Examples foo bar numbers 1 2 3 4 The leading symbol is called a functor The outermost functor in a term is called the principle functor The set of terms within the parenthesis are called arguments The number of arguments is called the compound term s arity In the above example foo has arity 1 and numbers has arity 4 It is often necessary to describe a whole set of terms which share the same functor and arity Prolog programmers usually denote such a set by writing functor and arity separated with a e g foo 1 numbers 4 This is known as a predicate indicator Lists Like many programming languages Prolog offers a list co
142. erminal ArgumentList Input Remainder Description This dynamic predicate is asserted by the parser when the grammar was compiled with the option dictionary_lookup Functor on The predi cate Functor 4 is assumed to be defined elsewhere by the programmer The parser then uses this predicate as a cache of bup_goal 4 calls which succeed This cache is used to avoid recomputation in subsequent parses You may wish to use retractall 1 to remove this predicate and flush the cache Examples Here we assume that we have compiled the file grammar bup defined above with the option dictionary_lookup vocabulary on assert vocabulary noun n vole volelX X X _553600 yes bup_goal s Args the cat chases the vole Args s np d the n cat vp v chases np d the n vole yes listing bup_wf_dict 4 bup_wf_dict det d the the A A bup_wf_dict noun n cat cat A A bup_wf_dict verb v chases chases A A 6 1 PREDICATES 245 bup_wf_dict noun n vole vole A A yes Errors None See also bup_compile 3 retractal1 1 6 1 6 bup_wf_goal 4 Synopsis bup_wf_goal NonTerminal ArgumentList Input Remainder Description This dynamic predicate is asserted by the parser when the compile option cache_goals on is given The parser then uses this predicate as a cache arguments to bup_goal 4 calls which succeed This cache is used
143. error Both arguments were uninstantiated type_error character Char The argument Char was not a character type_error integer Code The argument Code was not an integer representation_error character_code The argument Code was not a valid character code See also character 1 character_code 1 4 1 43 char_conversion 2 Synopsis char_conversion From To Description Updates the character conversion table so that current_char_conversion 2 can map the character From to To When called with From being identical to To the identity mapping any character conversion table entry for the argument character is removed The conversion table is used when un quoted terms are read by read_term 3 It is always a good idea to quote the arguments to char_conversion 2 so as to avoid any conversion problems Examples Note how quotes are used with arguments and with the functor name to avoid problems char_conversion a a yes char_conversion a b yes gt current_char_conversion a To To b yes char_conversion a a yes current_char_conversion a To 7 no 60 CHAPTER 4 BUILT IN PREDICATES Errors instantiation_error One of the arguments was not instantiated representation_error character One of the arguments was not a char acter See also character 1 current_char_conversion 2 4 1 44 character 1 Synopsis
144. ersed sin E Calculates the sine of the argument in radians This is an elementary function found in elementary_functions fasl sqrt E Calculates the square root of the argument This is an elementary function found in elementary_functions fasl gt _ gt E1 E2 Calculates the subtraction of E2 from El truncate E Calculates the integer which is equal to float_integer_part E Examples ensure_loaded runtime elementary_functions yes ensure_loaded runtime special_functions yes X is 99 9 X 99 9 4 1 PREDICATES yes X is A X 65 yes X is 99 X 99 yes X is abs 2 3 X 2 3 yes X is 1 245 X 6 2 yes X is atan 1 X 0 785398 yes X is 129 7 X 17 yes X is V X 18446744073709551608 yes X is 2 lt lt 3 X 16 yes X is 129 7 X 135 yes X is 16 gt gt 3 x 27 yes X is ceiling 1 5 X 2 7 96 CHAPTER 4 BUILT IN PREDICATES yes X is cos 1 X 0 540302 yes X is exp 1 X 2 718282 yes X is 2 3 X 8 7 yes X is factorial 3 X 6 yes X is float 3 X 3 0 yes X is float_fractional_part 3 14 X 0 14 yes X is float_integer_part 3 14 X 3 0 yes X is 2 3 X 0 666667 yes X is 2 3 X 0 7 yes X is 2 3 X 0 7
145. es Errors domain_error non_empty_list The argument L was the empty list 0 instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_semi_interquartile_range 2 13 1 17 sample_mean_absolute_deviation 2 Synopsis sample_mean_absolute_deviation L Result Description Result is the arithmetic mean of the absolute deviations of the members of the list of numbers L from the arithmetic mean of L This predicate behaves as if it were defined as sample_mean_absolute_deviation L Result sample_arithmetic_mean L Mean sample_absolute_deviation L Mean Result Examples sample_mean_absolute_deviation 1 2 3 R R 0 666667 yes 13 1 PREDICATES 325 Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_absolute_deviation 3 13 1 18 sample_median 2 Synopsis sample_median L Result Description Result is the median of the list of numbers L This predicate behaves as if it were defined as follows sample_median L Result sample_quantile L 0 5 Result Examples
146. ewritten to be C true Examples assertz foo 2 yes assertz foo 1 yes foo X print X nl fail print done nl 2 1 done X _521408 yes Errors instantiation_error The head of the argument C was not instantiated type_error callable Head The head of the argument C was not callable that is to say it was not a predication type_error callable Body The body of the argument C was not callable that is to say not a well formed body term permission_error modify static_procedure Proc The procedure to be modified was static 4 1 PREDICATES 45 See also assert 1 asserta 1 predication 1 well_formed_body_term 1 4 1 24 at_end_of_stream 0 Synopsis at_end_of_stream Description Equivalent to at_end_of_stream user_input Examples See at_end_of_stream 1 Errors See at_end_of_stream 1 See also at_end_of_stream 1 4 1 25 at_end_of_stream 1 Synopsis at_end_of_stream S Description Succeeds if the stream identified by the stream term S has the property end_of_stream at i e the stream position for S is at the end of the stream and there are no more data to be read S must be a stream term or a stream alias Examples skip_to_end_of_text_file Stream repeat get_char Stream _ at_end_of_stream Stream 1 46 CHAPTER 4 BUILT IN PREDICATES Errors instantiation_error The argument S was not instantiated domain_error stream_
147. ff Spying on the following list of predicates fact 2 yes remove_spypoint fact 2 yes debugging Debugging is on Tracing is off Spying on the following list of predicates yes Errors instantiation_error The argument PI was not ground type_error predicate_indicator PI The argument PI was not a valid predicate indicator See also debugging 0 nospy 1 14 3 10 spy 1 Synopsis spy PI 14 3 DEBUG PREDICATES 353 Description Calls add_spypoint 1 with the predicate indicator PI then sets the flag debug to the value on This predicate is defined as a prefix operator so the argument does not need parentheses Examples debugging Debugging is on Tracing is off Spying on the following list of predicates yes spy fact 2 yes spy fact 2 yes debugging Debugging is on Tracing is off Spying on the following list of predicates fact 2 yes Errors See add_spypoint 1 See also add_spypoint 1 debugging 0 nospy 1 14 3 11 trace 0 Synopsis trace Description Sets both of the flags debug and trace to the value on Examples trace true 0 O call static true 0 O exit static true 304 CHAPTER 14 DEBUG yes Errors None See also debug 0 nodebug 0 notrace 0 14 4 Debug Flags 14 4 1 debug Description A switch which engages or disengages the debugger Default Value off Possibl
148. g properly The user can follow a reconsult test fix cycle with dynamic versions of the procedure until the test is passed then the procedure can be compiled for greater efficiency Entire Prolog source files can be compiled The user supplies the input file name and the name of the file where the compiled result is to be written This output file contains Prolog terms which install compiled procedures into the code section These files of compiled procedures are typically known as fas1 files See absolute_file_name 3 for in formation on how the file extension fas1 can be used by predicates 15 1 Predicates 15 1 1 compile_file 2 Synopsis compile_file SourceFile DestinationFile Description Compiles the predicates in the file SourceFile and writes the compiled pred icates to the file DestinationFile The output file contains Prolog terms 307 398 CHAPTER 15 COMPILING and can be loaded with consult 1 reconsult 1 or ensure_loaded 1 Any compiled predicates loaded this way are static Any predicate which is de fined as dynamic with the dynamic compiler directive is not compiled but copied to the output file instead This allows the programmer to mix static and dynamic predicates Examples Imagine the contents of the file test pl were the following dynamic foo 1 foo X member X 1 2 3 bar X member X 1 2 3 The transcript below shows a simple compilation Note how the file test fasl is automati
149. gt V f var V But as we see from the expansion the variable will have to be instantiated before the call to phrase 3 or an exception will be thrown expand_term a gt B T _524768 B T a _544064 544032 phrase _524768 544064 544032 yes Using the grammar operator phrase 1 we can inline a call to the predi cate phrase 3 dcg_body_terminal gt phrase T From the example that follows we see that phrase 1 expands into phrase 3 where the extra two arguments are the representation of the list being pro cessed expand_term a gt phrase b T T a _544544 _544512 phrase b _544544 _544512 yes 224 CHAPTER 4 BUILT IN PREDICATES The two extra arguments that represent the list being processed can passed on to Prolog predicates with the grammar operator ca11 1 dcg_body_terminal gt call T The expansion adds the two extra arguments to build a call of cal1 3 expand_term a gt call c T T a _544096 _544064 call c _544096 _544064 yes Ordinary Prolog goals are introduced with the grammar operator 1 This operator s argument is a Prolog goal dcg_body_terminal gt T The goal is just copied verbatim into the expanded term expand_term a gt b T T a _543008 _542976 b _543008 _542976 yes The empty sequence is denoted by dcg_body_terminal gt It s expansion is a simple unificat
150. h_path 2 26 add_generate_message 1 27 add_message_hook 1 28 add_portray 1 29 add_portray_message 1 31 add_query_class_hook 1 32 add_query_input_hook 1 33 add_query_map_hook 1 35 add_spypoint 1 346 add_term_expansion 1 35 append 3 37 apply 2 37 arg 3 38 arity 2 40 ask_query 4 41 assert 1 42 asserta 1 43 assertz 1 44 assoc_to_list 2 233 at_end_of_stream 0 45 at_end_of_stream 1 45 atom 1 46 atom_chars 2 46 atom_codes 2 47 atom_concat 3 48 atom_index 3 49 atom_length 2 50 atomic 1 51 bagof 3 52 between 3 51 break 0 53 bup_compile 2 241 bup_compile 3 241 bup_fail_goal 2 242 bup_goal 4 243 bup_wf_dict 4 244 bup_wf_goal 4 245 byte 1 54 call 1 55 cal1 3 56 364 callable_term 1 57 case_shift 2 293 catch 3 57 char_code 2 58 char_conversion 2 59 character 1 60 character_code 1 60 chars_to_atom 3 294 chars_to_integer 3 295 chars_to_string 3 296 chars_to_words 2 296 chars_to_words 3 297 chi_squared_cdf 3 311 chi_squared_pdf 3 312 chi_squared_quantile 3 313 clause 2 61 close 1 62 close 2 62 compare 3 63 compile_file 2 357 compile_procedure 1 359 compose 3 247 compound 1 64 concatable_atom 1 64 consult 1 66 convert_char 2 66 copy_term 2 67 correspond 4 255 current_char_conversion 2 68 current_file_search_path 2 69 current_generate_message 1 70 current_input 1 70 current_message_hook 1 71 current_op 3 72 current_output 1 72 curr
151. he effect is that reconsult 1 does not remove previous definitions of these procedures This indicator has no effect outside the file it is defined unless the file is included in another file multifile foo 1 2 5 INTERRUPTING EXECUTION 7 2 4 7 Prolog Term A Prolog term that does not have the form of the previously defined di rectives is called as soon as it is read This is subtly different from the initialization 1 directive which schedules its argument to be called when loading has completed Example op 500 xfx gt Should the goal fail then a warning message is printed As an example consider the following directive fail It generates the following message The following goal failed fail 2 5 Interrupting Execution At any time during execution you can input control C to enter the interrupt handler If the system is in the middle of a garbage collection then the system will wait until garbage collection has completed before entering the interrupt handler You will then be presented with a menu of options Interrupt a abort c continue set debug flag The debugger will leap exit Prolog This is equivalent to a halt clear trace amp debug flags set trace amp debug flags The debugger will creep exit Prolog This is equivalent to a halt B O Pressing any one of the keys shown on the left of the menu will activate the choice You do not need to input enter return
152. he mean of a sample is already known In other cases sample_variance 2 should be used Examples sample_variance 1 1 1 1 V V 0 0 yes sample_variance 1 2 3 2 V V 1 0 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_variance 2 13 1 27 students_t_cdf 3 Synopsis students_t_cdf X N Answer Description Answer is the probability that Y lt X where Y is a random variable distributed according to the Student s t distribution with N degrees of freedom 334 CHAPTER 13 THE STATISTICS LIBRARY Examples students_t_cdf 2 1 Answer Answer 0 147584 yes Errors domain_error not_less_than_one N The argument N was less than 1 instantiation_error Fither the argument X or the argument N was an uninstantiated variable type_error integer N The argument N did not evaluate to an integer Also as the arguments X and N are evaluated errors may be thrown by eval 2 See also None 13 1 28 students_t_pdf 3 Synopsis students_t_pdf X N Answer Description Answer is the probability density at Y X where Y is a random variable dis tributed according to the Student s t distribution with N deg
153. hich was not a character syntax_error badly_formed_number The argument L could not be parsed See also character 1 number_codes 2 4 1 141 number_codes 2 Synopsis number_codes N L number_codes N L Description Succeeds if the name of the number N corresponds to the list of character codes L Examples number_codes 3 14 C C 51 46 49 52 138 CHAPTER 4 BUILT IN PREDICATES yes number_codes N 3 14 N 3 14 yes Errors instantiation_error Either both arguments were uninstantiated or N was uninstantiated and L was not ground type_error number N The argument N was instantiated but it was not a number type_error list L The argument L was instantiated but it was not a list representation_error character_code The argument L contained an el ement which was not a character code syntax_error badly_formed_number The argument L could not be parsed See also character_code 1 number_chars 2 name 2 4 1 142 once 1 Synopsis once T Description Succeeds if and only if ca11 T succeeds This predicate succeeds only once hence the name This predicate behaves as if it were defined as follows once T call T Examples once true true fail no Errors instantiation_error The argument T was not instantiated type_error callable T The argument T was not a callable term 4 1 PREDICATES 139 See also None 4 1 143 op
154. i 100 4 1 94 file_search_path 2 100 A L95 Pandata ook ee aba at eR BSE So ee 101 LLOG Plopt L soc ace pise ee ecos Ake Lew amp 2 102 ALF flush OU LPUEJO se tld a a p a ee we a 103 1108 ElDish output I ee ee se pe Be a N 103 LIDO Format 2 beh ke aoe we Oa te ao 104 AU IIOESEDAE S Escoria ae 105 ALS RREGOP Ss won ke i we bee Saw pe ew e 108 4 1 102 generate_message_line 3 109 4 1 103 generate_message_lines 3 110 a LOA get byte i coser Ee PRG ee ERE HS 111 a L105 get elec RARA 111 ALTIUG pet char L 2 i een Bawa er Rie rastras 112 AVANT Cet Chet Oo oe Sate PRES Ae ee eX 113 ALTOS Bet C0des Lo o a Ee e eS 114 AUD Cee EAS 2 RE Se ha e t 114 A EAN 115 A AA IA 116 A e y ee Ba we Bo BRE a 116 ALS Boo eee e bo cae Bk e ke eA 117 21 Vd BYERS LD 24 iow ee ee ra ee we 118 a AA 118 4 1 1161n character_c0d8 l ce s ooie siop oe e oeae 119 41 11 infir op specifier i opos ee he 120 A TIAS Lo oo oe aps ea Oe ee we 120 ME Ode Le naea bon eS Pe i EA ee ee 121 ARIT o ike RS eG Se ee Ee ee a 121 Ai E 1 e e oea SESE EEO ESS oS SECS 122 41 122 keysort 2 o sades ae ba eee ee RA ES a 122 ll Lealtad scoscasiasss decorar LRG RA 123 A NASA Stine O hae Pe ee ee ee d 124 ALMAS De ek ak GE ee bdo e A 124 SAG TAS tae 2 wo Be Ge Be ed OG Re Ss hae 125 e AI ee Pears ee Se wea as 126 d lT Smene 2 ok og OS ede AA ew 127 4 1 129message_hook 3 00 0000 4 127 MS eee te ee eel So ee he he E 129
155. icates current_prolog_flag 2 and set_prolog_flag 2 Whitespace Terms can be separated by spaces tabs and other unprintable characters These separators a k a whitespace have no meaning Specifically a whites pace character is a Unicode code of 32 or less or a Unicode code greater than or equal to 127 and less than or equal to 160 Those Unicode codes which can be used as whitespace are those accepted by the built in predicate prolog_lexical_ws 1 Comments There are two types of comment C style comments which start with and end with Everything contained between these is treated as whites pace Another type of comment starts with a and anything between that character and the end of the current line is considered whitespace Examples Iaa comment As am I 3 1 SYNTAX 15 Operators Those terms which have functors with arity of one or two may be written in prefix infix or postfix notation In this case these functors are called operators Just like operators found in expressions in other languages Pro log operators can be described in terms of priority a k a precedence and associativity See the documentation for the built in predicates op 3 and current_op 3 for details In the demonstrations that follow we use calls of op Priority Associativity AtomName to specify the operator The meaning of the three arguments are Priority This is an integer between 0 and 1200 inclusive The lower of two
156. ile One way to do this is with the following call ensure_loaded runtime assoc An empty association list is the empty binary tree and this is represented by the atom t In the case of a non empty association list each element of the list is represented by one node of the binary tree The binary tree node structure has the form t Key Value LeftTree RightTree For any key K found in LeftTree we know that K lt Key For any key K found in RightTree we know that K 0 gt Key There is no other key K in LeftTree or RightTree such that K Key 5 1 Predicates 5 1 1 assoc_to_list 2 Synopsis assoc_to_list Assoc List assoc_to_list Assoc List Description Succeeds if the list List contains all of the Key and Value pairs in the association list Assoc Examples put_assoc b t b Assoc1 put_assoc a Assoc1 a Assoc2 put_assoc c Assoc2 c Assoc3 233 234 CHAPTER 5 assoc_to_list Assoc3 Lst Associ t b b t t Assoc2 t b b t a a t t t Assoc3 t b b t a a t t t c c t t Lst a a b b c c yes assoc_to_list Assoc la a b b c c Assoc t b b t a a t t t c c t t yes Errors None See also None 5 1 2 get_assoc 3 Synopsis get_assoc Key Assoc Value get_assoc Key Assoc Value get_assoc Key Assoc Value Description THE Assoc LIBRARY Succeeds if the association list Assoc associates Key with Value Examples put_assoc key0 t
157. inished yes grammar pl yes ensure_loaded runtime readin yes read_in S bup_goal s Tree S O The cat chases the mouse S the cat chases the mouse Tree s np d the n cat vp v chases np d the n mouse yes In the above example we ve used bup_compile 2 which gives us the de fault options for BUP parser generation There is a BUP compile predicate bup_compile 3 which takes a list of options as its third argument These options cover the caching of parse results to avoid recomputation and the segregation of grammar rules and dictionary The grammar we ve been using has only seven terminal symbols the a cat dog mouse chases scares and each of these is defined in the grammar 239 If we wanted to be able to parse thousands of terminal symbols then the grammar would be quite large To solve this problem we can separate the grammar rules and the dictionary Here a dictionary means a set of terminal symbols To do this we instruct the BUP compiler to generate a parser that calls a dictionary look up predicate when terminals aren t found in the grammar We could then write this predicate to dynamically parse these terminals e g search a large file on disk containing lots of words looking for the grammar terminal passed as an argument to the predicate The problem with this solution is that terminal processing now takes longer time potentially much longer If
158. ion expand_term a gt T T a _542080 _542048 _542080 _542048 7 yes Note that these two read terms are not the same a a gt According to O K90 confusing the two is a common mistake Actual terminals are Prolog terms in a list dcg_body_terminal gt dcg_terminals Expansion of actual terminals constrains the two list arguments i e the list prefix is specified expand_term a gt b c T T a _543216 _ 543184 _543216 b c _543184 yes 4 2 DEFINITE CLAUSE GRAMMAR 225 Non determinism can be controlled with the grammar operator 0 which behaves just as the predicate with the same name does in Prolog goals dcg_body_terminal gt The expansion is straightforward and comparing the following two examples we can see the DCG cut really is the Prolog cut expand_term a gt b T T a _542800 _542768 _542800 544032 b _544032 _542768 yes expand_term a gt b T T a _543248 543216 _543248 _544480 b _544480 543216 yes The DCG grammar is designed to give the grammar operators relative priorities in line with the Prolog operator table Parentheses can be used to override this dcg_body_terminal gt dcg_body Examples expand_term a gt b T T a _542496 _542464 b _542496 _542464 yes expand_term a gt b
159. ion of T1 and T2 This predicate is the usual append 3 a k a conc 3 found in Prolog textbooks Examples append a b c d e f L L a b c d e f yes append L d e f a b c d e f L a b c yes Errors None See also None 4 1 15 apply 2 Synopsis apply T1 T2 Description Behaves as if it were defined as follows apply Functor Args Call Functor Args call Call 38 CHAPTER 4 BUILT IN PREDICATES Examples X print apply X 99 nl 99 X print yes Errors instantiation_error One of the arguments T1 or T2 was not instantiated type_error list T2 The argument T2 was not a list domain_error non_empty_list The argument T2 was the empty list 0 See also ca11 1 4 1 16 arg 3 Synopsis arg 1 T X Description X is the 1 argument of the compound term T This predicate will fail if I is zero or if I is greater than the arity of the functor of T Examples arg 1 foo a b Arg Arg a yes Errors instantiation_error Fither I or T were not instantiated domain_error not_less_than_zero I The argument I was less than zero type_error compound T The argument T was not a compound term 4 1 PREDICATES 39 See also None 4 1 17 Arithmetic comparison with evaluation Synopsis L R L R L lt R L lt R L gt R L gt R Description Arithmetic compar
160. iption Registers the predicate identified by the predicate indicator A 5 as a query class hook These hooks give the user an opportunity to define their own classes of queries The mode specification for the hook is hook QueryClass Prompt InputMethod MapMethod FailureMode The five arguments of the hook are QueryClass A term used to identify the class being described by the hook If the first argument to ask_query 4 is unifies with QueryClass then the query class described by this hook is selected Prompt A term shown to the user as an indication that input is being re quested InputMethod See query_input 3 MapMethod See query_map 4 FailureMode See ask_query 4 Examples assert swedish_query_class_hook swedish_yes_no_maybe gt j n eller k line char ja Jj nej Nn kanske Kk help_query yes add_query_class_hook swedish_query_class_hook yes ask_query swedish_yes_no_maybe Input j n eller k K Input kanske yes 4 1 PREDICATES 33 Errors instantiation_error The argument A was not instantiated type_error atom A The argument A was not an atom See also current_query_class_hook 1 del_query_class_hook 1 4 1 11 add_query_input_hook 1 Synopsis add_query_input_hook A Description Registers the predicate identified by the predicate indicator A 3 as a query input hook These hooks give the user an opportunity to define their own q
161. iption Answer is the X quantile 0 lt X X lt 1 of the x distribution with N degrees of freedom Examples chi_squared_quantile 0 995 10 A A 25 188173 yes chi_squared_quantile 0 005 10 A A 2 159888 Errors domain_error chi_squared_out_of_bounds X N One of the follow ing holds for the arguments X and N e X lt 0 1 N lt 2 e X lt 0 01 N lt 3 domain_error not_greater_than_one X The argument X was greater than 1 domain_error not_less_than_one N The argument N was less than 1 domain_error not_less_than_zero X The argument X was less than 0 instantiation_error Either the argument X or the argument N was an uninstantiated variable type_error integer N The argument N did not evaluate to an integer Also as the arguments X and N are evaluated errors may be thrown by eval 2 See also None 314 CHAPTER 13 THE STATISTICS LIBRARY 13 1 4 f_cdf 4 Synopsis f_cdf X M N Answer Description Answer is the probability that Y lt X where Y is a random variable distributed according to the F distribution with M numerator and N denominator degrees of freedom Examples _cdf 1 5 2 Answer Answer 0 431201 yes Errors domain_error not_less_than_one I Either the argument M or the ar gument N was less than 1 domain_error not_less_than_zero X The argument X was less than 0 instantiation_error At least one of the arguments X M or
162. ison of arithmetic expressions L and R The expressions L and R are evaluated with eval 2 and then compared L R L equal to R L R L not equal to R L lt R L less than R L lt R L less than or equal to R L gt R L greater than R L gt R L greater than or equal to R Examples P 3 3 gt 3 yes 3 0 3 yes 4 lt 5 yes 5 4 10 2 yes Errors Errors are not thrown by these predicates The evaluation of the arguments may however throw errors See eval 2 40 CHAPTER 4 BUILT IN PREDICATES See also eval 2 4 1 18 Arithmetic comparison without evaluation Synopsis equal N1 N2 less_than N1 N2 greater_than N1 N2 less_than_equal N1 N2 greater_than_equal N1 N2 Description Arithmetic comparison of numbers N1 and N2 These predicates do not eval uate their arguments Examples equal 3 0 3 yes less_than 4 99 yes greater_than 5 4 yes less_than_equal 3 3 yes greater_than_equal 4 4 yes Errors None See also None 4 1 19 arity 2 Synopsis arity Term Arity 4 1 PREDICATES 41 Description Succeeds if the arity of the principle functor of Term is Arity This predicate behaves as if it were defined as arity Term N functor Term _ N Examples arity 9 0 yes arity foo 1 2 3 X X 37 yes Errors See functor 3 Se
163. ist Description Succeeds if Element is a member of List Examples member 1 1 2 3 yes member 4 1 2 3 no member A B A _22816 B _22816 _29616 yes Errors None See also None 4 1 129 message_hook 3 Synopsis message_hook Severity Message Lines 127 128 CHAPTER 4 BUILT IN PREDICATES Description Prints a message with a severity prefix The following are the valid severity values for the argument Severity banner The message has no prefix error The message is prefixed with help The message has no prefix informational The message is prefixed with none The message has no prefix query The message has no prefix silent The message is not output warning The message is prefixed with The arguments Message and Lines are two different representations of the same message This predicate only uses Lines which are displayed on the stream user_error The reason both are given is to provide a user hook registered with add_message_hook 1 more information so that it can gener ate more useful error messages The usual method of generating Lines from Message is generate_message Msg L generate_message_lines Lines L Examples Msg error instantiation_error instantiation_error variable V 1 generate_message Msg L generate_message_lines Lines L message_hook error Msg Lines ERROR Error class instanti
164. it were defined as follows sample_quantile L Q Result sample_quantile L Q 0 0 1 0 Result Examples sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 Result Result 5 0 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error Either the argument L or the argument Q was an uninstantiated variable type_error list L The argument L was not a list Also as the argument Q and all members of the argument L are evaluated errors may be thrown by eval 2 See also sample_quantile 7 13 1 21 sample_quantile 7 Synopsis sample_quantile L Q P1 P2 P3 P4 Result Description Result is the 1 Q quantile of the list of numbers L The arguments P1 P2 P3 and P4 are parameters which control the computation of Result The specification of that computation is S sort L x P1 length S P2 Q Result Sis Sta Slej P3 P4 fractional_part x Popular values for the parameters are shown in the following table 328 CHAPTER 13 THE STATISTICS LIBRARY P1 P2 P3 P4 Name 0 0 1 0 Inverse CDF 0 0 0 1 Linear interpolation California Dept of Publ Works 12 0 0 0 Closest element 1 2 0 0 1 Linear interpolation Hazen s Hydrologist 0 1 0 1 Mean estimate Weibull 1 1 0 1 Mode estimate 3 8 1 4 0 1 Normal distribution estimate Examples sample_quantile 1 2 3 4 5 6 7 8 9 10 0 5 0 0 1 0 InverseCDF Inverse
165. lass_hook ynm_class_hook yes ask_query yes_no_maybe Input y n or m m Input maybe yes Errors instantiation_error The argument A was not instantiated type_error atom A The argument A was not an atom 4 1 PREDICATES 35 See also ask_query 4 current_query_input_hook 1 del_query_input_hook 1 query_class 5 query_input 3 query_map 4 4 1 12 add_query_map_hook 1 Synopsis add_query_map_hook A Description Registers the predicate identified by the predicate indicator A 4 as a query map hook The purpose of query mapping is to translate map user input A hook lets the user define their own such mappings An example of query map hook could be hook MapMethod RawInput Result Answer MapMethod is a term used to identify the mapping being described by the hook The query class selects the mapping method RawInput is the term to be mapped Result is the result of the mapping Answer is unified with the atom success upon a successful mapping Any other atom would indicate failure Examples See add_query_input_hook 1 for an example Errors instantiation_error The argument A was not instantiated type_error atom A The argument A was not an atom See also ask_query 4 current_query_map_hook 1 del_query_map_hook 1 query_class 5 4 1 13 add_term_expansion 1 Synopsis add_term_expansion A 36 CHAPTER 4 BUILT IN PREDICATES Description Registers the predicate iden
166. lause to recognise or generate simple English noun phrases noun_phrase Input0O Rest det InputO Input1 noun Input1 Rest Here s an example of what we ve done noun_phrase A B A the cat _524032 B _524032 A the dogl_524032 B _524032 no Here we do something similar for verbs and verb phrases verb chases Rest Rest verb_phrase Input0 Rest verb Input0 Input1 noun_phrase Inputi Rest Building upon what we ve done so far We can easily recognise or generate sentences sentence Input noun_phrase Input Rest verb_phrase Rest Example 4 2 DEFINITE CLAUSE GRAMMAR 219 sentence the cat chases the dog yes We can generate or recognise the same simple English language subset using a DCG like this dcg_det gt the dcg_noun gt cat dcg_noun gt dog dcg_verb gt chases dcg_noun_phrase gt dcg_det dcg_noun dcg_verb_phrase gt dcg_verb dcg_noun_phrase dcg_sentence gt dcg_noun_phrase dcg_verb_phrase The language defined is dcg_sentence S S the cat chases the cat S the cat chases the dog S the dog chases the cat S the dog chases the dog no As can be seen specifying a language with a DCG is much simpler than writing Prolog code by hand and quite surprisingly there is very little if any loss in performance In fact the Prolog code created for the
167. ld end up in a recursive call to the debugger Skip goal The flag trace is set to off for the duration of the current goal invocation This command only has an effect at call events Upon any other event a skip is equivalent to a creep 346 CHAPTER 14 DEBUG e Exception A prompt is displayed and a Prolog term is read The read term is then passed to throw 1 h Help The list of commands is displayed Help See above w Write goal The current goal is passed to writeq 1 Command A prompt is displayed and a Prolog term is read the flags debug and trace are both set to off the term which was read is passed to call 1 finally the flags debug and trace are both set to on Note that if you gave the command nodebug then it would have no effect as debugging and tracing would be turned on upon return If you want to turn off debugging then use the no debug command described above Debugging The predicate debugging 0 is called Spy The current goal s predicate indicator is passed to add_spypoint 1 Nospy The current goal s predicate indicator is passed to remove_spypoint 1 14 3 Debug Predicates 14 3 1 add_spypoint 1 Synopsis add_spypoint PI Description Places a spypoint on the predicate identified by the predicate indicator PI It is possible to have a spypoint placed on a predicate before it is defined The predicates that are marked for spying can be queried with the predicate debugging 0 14 3
168. les Description This is the notation used to re consult a list of files Elements of the list are passed as arguments to consult 1 unless they are prefixed with 1 in which case they are passed as arguments to reconsult 1 instead Examples slask foo slask foo yes Errors None See also consult 1 reconsult 1 4 1 89 ensure_loaded 1 Synopsis ensure_loaded T 4 1 PREDICATES 91 Description If the file T has previously been consulted then do nothing Otherwise call consult T Examples ensure_loaded slask foo yes Errors instantiation_error The argument T was not instantiated See also consult 1 reconsult 1 4 1 90 eval 2 Synopsis eval E N Description Evaluates the expression E to give the number N A valid expression is either a number or a compound where all arguments are valid expressions and the functor is one of a predefined set of arithmetic functors Those arithmetic functors which represent elementary functions are im plemented by internal predicates found in the file elementary_functions fasl and this will need to be loaded before these can be used The internal predi cates implementing the special function s arithmetic functors are found in the file special_functions fasl and again this will have to be loaded before use A number evaluates to itself A list with a single element which is a number evaluates to that number A compound with
169. log_flag integer_rounding function V V toward_zero yes Errors type_error atom F The argument F was neither uninstantiated nor an atom See also set_prolog_flag 2 76 CHAPTER 4 BUILT IN PREDICATES 4 1 67 current_query_class_hook 1 Synopsis current_query_class_hook F Description Succeeds if at some point add_query_class_hook F has been called to add the procedure specified by the predicate indicator F 5 Examples current_query_class_hook F no add_query_class_hook foo yes current_query_class_hook F F foo yes del_query_class_hook foo yes current_query_class_hook F no Errors None See also add_query_class_hook 1 del_query_class_hook 1 4 1 68 current_query_input_hook 1 Synopsis current_query_input_hook F Description Succeeds if at some point add_query_input_hook F has been called to add the procedure specified by the predicate indicator F 3 4 1 PREDICATES TT Examples current_query_input_hook F no add_query_input_hook foo yes current_query_input_hook F F foo yes del_query_input_hook foo yes current_query_input_hook F no Errors None See also add_query_input_hook 1 del_query_input_hook 1 4 1 69 current_query_map_hook 1 Synopsis current_query_map_hook F Description Succeeds if at some point add_query_map_hook F has been called to ad
170. lution line char yes 0 n no help_query query_class goal term query query_class yes_or_no y or n line char yes Yy no Nn help_query query_class yes_no_proceed y n p S a or line char yes Yy no Nn proceed Pp suppress Ss abort Aa help_query Examples None Errors None See also ask_query 4 add_query_class_hook 1 query_input 3 query_map 4 4 1 184 query_input 3 Synopsis query_input InputMethod Prompt Input Description This predicate is used internally by ask_query 4 where it reads prompted input from the user The argument Input is the final result The argument InputMethod determines how the input is gathered Possible values for this argument are line The input is read using query_read_line user_input Input term Options The input is read using read_term Input Options FinalTerm term Term Options Input is read using read_term Term Options and Input is unified with FinalTerm The argument Prompt is a term that is passed to prompt 1 before input is gathered The old prompt is restored upon completion of input 4 1 PREDICATES 171 Examples query_input line ok gt Line ok gt This is a line Line 84 104 105 115 32 105 115 32 97 32 108 105 110 101 46 10 yes Errors None See also add_query_input_hook 1 ask_query 4 query_read_line 2 4 1 185 query_m
171. mode M Mis either read write or append input This is an input stream output This is an output stream alias A One of the aliases of the stream is A position P Thecurrent position of the stream is P See set_stream_position 2 end_of_stream S Designates the stream position in terms of the end of the stream S is one of at The stream is currently at its end past The stream is currently past its end not The stream is neither at nor past its end eof_action A Designates what should happen should an program try to input from the stream when the current position is past the end A is one of error An exception is thrown eof_code An error code is returned reset The stream is reset so that it is no longer past the end of stream reposition B Designates whether or not the stream can be repositioned B is either true or false type T Designates the type of the stream T is either binary or text character_encoding E Designates how the stream characters are encoded obviously meaningless for binary streams E is one of ascii This is an ASCII encoded stream latin_1 This is an Latin 1 ISO 8859 1 encoded stream utf_8 This is an Unicode UTF 8 encoded stream utf_16be This is an Unicode UTF 16BE encoded stream utf_16le This is an Unicode UTF 16LE encoded stream utf_32be This is an Unicode UTF 32BE encoded stream utf_32le This is an Unicode UTF 32LE encoded stream 196 CHAPTER 4 BUILT IN PREDICATES Examples s
172. mples 123 123 The format of a floating point number is more involved than that of the integer It is best described formally with a context free grammar In the following the lt radix digit gt grammar class is undefined because it was defined above 12 CHAPTER 3 THE PROLOG LANGUAGE lt floating point number gt lt floating point number gt lt floating point number gt lt integer gt lt fraction gt lt exponent gt lt integer gt lt fraction gt lt fraction gt lt exponent gt lt floating point number gt lt fraction gt lt integer gt lt radix digits gt lt integer gt lt radix digits gt lt fraction gt lt radix digits gt lt exponent gt e lt signed integer gt lt exponent gt E lt signed integer gt lt signed integer gt lt radix digits gt lt signed integer gt lt radix digits gt lt signed integer gt lt radix digits gt lt radix digits gt lt radix digit gt lt radix digits gt lt radix digit gt lt radix digits gt From this we see that only the fraction part must be given all other parts are optional Examples 1 23 1 2e3 1 2e 3 1 2E 3 23 As mentioned above numbers can be given in a radix other than decimal The radix to be used is indicated by a prefix Examples of numbers with radix prefixes Oxdeadbeef 16 deadbeef 0b1011 2 1011 0017 818 Of the examples just given the first two w
173. n or equal to zero The argument Whence is an atom and it determines how Offset is to be used Possible values for Whence are bof The stream offset is set to the beginning of the file plus Offset current The stream offset is set to the current position of the file plus Offset eof The stream offset is set to the end of the file plus Offset Examples open test_seek txt write Streaml lalias alias reposition true seek Stream1 0 bof 0 seek Stream1 3 bof 3 seek Stream1 0 eof 0 seek Stream1 0 bof 0 write Stream1 efg seek Stream1 0 current 3 close Stream1 Streaml stream 3 4 1 PREDICATES 181 yes Errors domain_error not_less_than_zero Offset The argument Offset was an integer less than zero domain_error seek_whence Whence The argument Whence was not valid domain_error stream_or_alias Stream The argument Stream was not a valid stream term or alias atom existence_error stream Stream The argument Stream refers to a nonex istent stream instantiation_error One of the arguments Stream Offset or Whence was not instantiated permission_error reposition stream Stream Either the argument Stream refers to a stream that was not opened with the option reposition true or the underlying file system did not permit the changing of the byte offset type_error atom Whence The argument Whence was not an atom type_error integer Offset The argument
174. n_character C The argument C was instantiated but not a valid input character See also get_char 2 4 1 152 peek_code 1 Synopsis peek_code C Description Behaves as if it were defined as follows peek_code Code current_input S peek_code S Code Examples See peek_code 2 Errors See peek_code 2 See also current_input 1 peek_code 2 148 CHAPTER 4 BUILT IN PREDICATES 4 1 153 peek_code 2 Synopsis peek_code S C Description Succeeds if C would be the next character code read from the text stream S Examples test_peek_code open test_file txt read Stream peek_code Stream C get_code Stream C close Stream Errors domain_error stream_or_alias S The argument S is not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error The argument S was not instantiated permission_error input past_end_of_stream S Tried to read past the end of the stream permission_error input stream S There is a lack of permission to read from stream S permission_error input binary_stream S The argument S refers to a binary stream representation_error in_character_code C The argument C was in stantiated but was not a valid input character code type_error integer C The argument C was instantiated but was not an integer See also None 4 1 PREDICATES 149 4 1 154 phrase 2 Synopsis phrase R L
175. nd existentially quantify the variable Y bagof X Y member X Y 1 2 3 4 5 6 L _521856 _522720 1 3 5 Y X Y L yes Examples See description above Errors instantiation_error The argument Goal was uninstantiated type_error callable Goal The argument Goal was not callable type_error list Bag The argument Bag was neither a list nor a partial list See also findall 3 setof 3 4 1 35 break 0 Synopsis break Description Initiates a new top level loop The debugging flags are cleared before starting the new top level loop and they are restored upon an abort 54 CHAPTER 4 BUILT IN PREDICATES Examples break Entering break level 1 1 break Entering break level 2 2 abort yes 1 abort yes Errors None See also abort 0 4 1 36 byte 1 Synopsis byte B Description Succeeds if B is a valid byte Behaves as if it were defined as follows byte Byte integer Byte Byte gt 0 Byte lt 255 Examples byte 199 yes Errors None 4 1 PREDICATES 59 See also None 4 1 37 C 3 Synopsis C 7A 7B C Description This predicate is provided for historical reasons as some pieces of Prolog code expect it to be present C 3 behaves as if it were defined as follows C C HITI Hy T Examples C one two three one Rest Rest two three yes Er
176. nopsis predication T Description Succeeds if T is a predication This definition of predication is i all atoms are predications and 1i all compound terms are predications Examples predication foo yes predication foo _ _ yes Errors None See also atom 1 compound 1 4 1 162 prefix_op_specifier 1 Synopsis prefix_op_specifier T 4 1 PREDICATES 155 Description Succeeds if T is an prefix operator specifier Examples findal1 0 prefix_op_specifier 0 L 0 _522304 L fx fy yes Errors None See also current_op 3 op 3 op_specifier 1 infix_op_specifier 1 postfix_op_specifier 1 4 1 163 print 1 Synopsis print T Description Behaves as if it were defined as follows print Term current_output S print S Term Examples See print 2 Errors See print 2 See also current_output 1 print 2 156 CHAPTER 4 BUILT IN PREDICATES 4 1 164 print 2 Synopsis print S T Description Behaves as if it were defined as follows print Stream Term write_term Stream Term portray true Examples See write_term 2 Errors See write_term 2 See also write_term 2 4 1 165 print_message 2 Synopsis print_message S M Description Prints the message M with severity S An attempt is made to find an appro priate portray message hook If such a hook exists it is called Otherwise the messag
177. nslation Note that this is a consult and not a reconsult Should you consult the same file twice then you will have two copies of all read terms in the clause store Any compiled procedures which are loaded with consult 1 replace any previous definitions In this case consult 1 acts as reconsult 1 does Examples consult slask foo yes Errors instantiation_error The argument F was not instantiated See also absolute_file_name 2 reconsult 1 2 4 1 54 convert_char 2 Synopsis convert_char C1 C2 Description Succeeds if C2 is the character conversion of C1 which is defined by the flag char_conversion and the predicate current_char_conversion 2 The predicate behaves as if 1t was defined as follows convert_char Char Converted current_prolog_flag char_conversion on current_char_conversion Char Converted 1 convert_char Char Char 4 1 PREDICATES 67 Examples char_conversion z y yes convert_char z C C y yes char_conversion z z yes convert_char z C C 2 7 yes Errors See current_char_conversion 2 See also char_conversion char_conversion 2 current_char_conversion 2 4 1 55 copy_term 2 Synopsis copy_term T1 T2 Description Succeeds if T2 is a copy of T1 where each uninstantiated variable in T1 is mapped to a newly allocated variable in T2 The predicate behaves as if it was
178. nstruction mech anism A list is represented by a compound structure which by convention is the functor 2 The first argument is the head of the list and the second argument is the tail The empty list is represented by the atom 1 Example the list of even integers greater than zero and less than ten would be represented as gt 2 4 6 E By 110999 As lists are so frequently used a convenient syntax is provided The term gt A B can be input and printed as AIB and the term A B C can be input and printed as A B C More generally the term A TB Caan PCT vee ned J can be input and printed as AI BI Lee YIZz This can be further shortened to the equivalent A B YIZ Finally if the last list element is the empty list then there is another short cut the term A B YIO can be input and printed as 14 CHAPTER 3 THE PROLOG LANGUAGE A B Y Some types of lists can be built using quotation marks However the contents of the list depends upon the value of the Prolog flag double_quotes If the flag is set to codes then the Prolog term ABCDEFG is equivalent to 65 66 67 68 69 70 71 The numbers are the Unicode codes of the corresponding letters If the value of the Prolog flag double_quotes is set to chars then the Prolog term ABCDEFG is equivalent to PA 5 2B en 2D A E A F A 2 See the documentation for the built in pred
179. nt A was not a list or the argu ment to s was not a list type_error number T The argument to f was not a number See also None 4 1 101 functor 3 Synopsis functor T F 7A functor T F A Description Succeeds if the term T has the principle functor F with arity A Examples functor f al a2 F A F f A 2 yes functor T f 2 T _528960 _528976 4 1 PREDICATES 109 yes functor three F A three 0 gt m 1 yes functor 3 F A F 3 A 0 yes functor 3 0 F A float A 32 H l yes Errors instantiation_error Either both T and F were not instantiated or both T and A were not instantiated type_error atomic F The argument T was uninstantiated and A was in stantiated and F was not atomic type_error atom F The argument T was uninstantiated and A was in stantiated and F was not an atom type_error integer A The argument T was uninstantiated and A was instantiated and A was not an integer domain_error not_less_than_zero A The argument T was uninstanti ated and A was instantiated and A was less than zero representation_error max_arity The argument T was uninstantiated and A was instantiated and A was not less than or equal to the value of the flag max_arity See also None 4 1 102 generate_message_line 3 Synopsis generate_message_line A B C 110 CHAPTER 4 BUILT IN PREDICA
180. nt B was not a list Also as the arguments A B and Alpha are evaluated errors may be thrown by eval 2 See also None 338 CHAPTER 13 THE STATISTICS LIBRARY Chapter 14 Debug Most Prolog debuggers are variations of the DECsystem 10 implementation BBP 81 which traces Prolog execution by displaying messages at certain execution events corresponding to the ports of the Byrd Box model Byr80 The debugger described here is just another variation of this classic design but instead of providing an inferior rewrite of the usual Byrd Box description we ll try to reconstruct a simplified version from first principles Hopefully this way the user will gain a useful insight into why the debugger is the way it is 14 1 A Simplified Tracer Imagine we were interested in examining the execution of the goal a given the following clauses a t D od b true d true We ll assume that c is not defined which means that as a goal it will fail However from this simple program we can see that our original goal a should succeed since the sub goal d succeeds Let s actually demonstrate that this is true by giving our goal to the most basic of Prolog interpreters demo 1 demo true demo G1 G2 debug G1 debug G2 demo G1 G2 debug G1 debug G2 demo G clause G C demo C When we feed our goal a as an argument to demo 1 we see that it succeeds so all is well Whilst this basic interpre
181. o prolog_lexical_digit 1 prolog_lexical_lower_case_letter 1 prolog_lexical_symbol 1 prolog_lexical_ws 1 4 1 174 prolog_lexical_ws 1 Synopsis prolog_lexical_ws Code Description Succeeds if the character code Code represents a character can be used as whitespace in Prolog source All whitespace input is ignored Examples prolog_lexical_upper_case_letter 0 P yes prolog_lexical_upper_case_letter 0 p no Errors None See also prolog_lexical_digit 1 prolog_lexical_lower_case_letter 1 prolog_lexical_symbol 1 prolog_lexical_upper_case_letter 1 4 1 175 prompt 1 Synopsis prompt T prompt T 164 CHAPTER 4 BUILT IN PREDICATES Description This predicate is used to set or query the prompt term displayed when input is read from the user If T is an uninstantiated variable then it is unified with the prompt term If T is not a variable then the prompt term is set to T Note that the top level loop calls prompt before asking for input Examples prompt 0K gt read X OK gt hello X hello yes prompt T T yes Errors None See also None 4 1 176 public_procedure 1 Synopsis public_procedure T Description Succeeds if the predicate indicator T identifies a public procedure which is equivalent to a dynamic predicate This predicate behaves as 1f it was defined as public_procedure P procedure_property P
182. o a a oe e e r ea e e hem Behe IOLI printattee Lo ous d be arb a ee g 10 1 2 print tree 2 2 ooa po enie e OR RE RE readin library Predicates e gt eanes i bee RRR EGA Rw ia E AI AA In erda Re See ee ee ee xl 263 264 264 265 266 266 267 268 268 269 270 271 273 273 273 274 274 275 276 276 277 277 278 279 279 280 280 281 281 282 285 285 285 286 xii CONTENTS 12 The readsent library 293 AL Predicates kee oe a e Re Da oe we Ae S 293 C2 case SETE ee bk a A ae bees 293 12 1 2 chars Eo o a A PEE ee ae A 294 12 1 3 Chars to integer s ore ae n e 295 IDA chars to String 3 e occain ai eo eh AE 296 12 1 5 chars to words 2 o a si ea aati oa RE a 296 IZ chars to Words 2 ia eop a woni poe ee a 297 lr DPE E eee kk aG e ee te a ee ae 298 IS is endfile l osd ecco we ee PE ON ae a e a e 299 LLO IS layout l stis bk o ea ee 299 12 1 10 is letter 1 2 ia ce a eee ee hele we eee Le me 300 12 111 is lower ce Be cee Ce eee Se eS 300 POA lla Dent i spesa ee e da 301 A e y oe ee Gee eek eae 301 12 Lae period Tsk ee a cdi eee Ss 302 Tas punct I kek ok ee ee ee ee oe o 302 12 1 1018 _upp r i a cirese ni eS Se ek AA 303 TOL read lanes sk ny ek Re Ae eh ee a 303 EAS A es ore hs a do Re ee e SO 304 P2118 resdssent l cocos 305 12 1 20 read Sent 2 645 o koa dd he aa dk a 305 12 1 21read_sentence l o 306 12 1 22read_sentence 2 0 o 307 EXA IS PEA weet es eR Ra ee ew
183. o that it is not past the end of file reposition false This stream may not be repositioned reposition true This stream may be repositioned type binary This is a binary stream type text This is a text stream If any two terms in O conflict with each other then the last of the two terms given takes precedence The default options are type text reposition false eof_action eof_code and character_encoding utf_8 Examples test open test_file txt write Stream write Stream hello nl Stream close Stream Errors domain_error io_mode M The argument M was not a valid I O mode domain_error source_sink F The argument F was not a valid source sink domain_error stream_option 0 The argument O contained an invalid option 4 1 PREDICATES 143 existence_error source_sink F The file referenced by F does not exist instantiation_error The arguments F M and O were not ground permission_error open source_sink F There was a lack of permis sion to open F type_error atom M The argument M was not an atom type_error list 0 The argument O was not a list type_error variable S The argument S was not a variable See also absolute_file_name 2 close 1 io_mode 1 source_sink 1 stream_property 2 4 1 146 op_specifier 1 Synopsis op_specifier T Description Succeeds if T is an operator specifier Examples findal1 0 op_specifier 0 Ops D _522304 Ops fx
184. o you may need to change this to suit your installation See the documentation for add_file_search_path 2 The last term read in any Prolog source file must be followed by whitespace a newline a tab a space or a comment This is the reason behind the comment on the last line 2 2 Queries The prompt tells you that the system is ready for a query The system will now input lines until it has read a full Prolog term followed by a full stop If more than one line needs to be read then on subsequent lines the prompt is changed to print 1 print 2 nl 12 yes If the query contains any variables these are reported upon success member X one two three X one The question mark shown is another prompt You can now either type followed by enter return for more solutions member X one two three X one X two X three no Or you can just input enter return for a new query prompt member X one two three X one yes 2 3 MESSAGES 5 2 3 Messages Errors warnings and informational messages from the system are prefixed by one of the characters or You can also generate such messages using print_message 2 print_message error This is an error This is an error yes print_message warning This is a warning This is a warning yes print_message informational This is information
185. ody_conjunction dcg_body_conjunction gt dcg_body_not dcg_body_not gt dcg_body_not dcg_body_not gt dcg_body_terminal dcg_body_terminal gt V fvar V dcg_body_terminal gt phrase T dcg_body_terminal gt call T dcg_body_terminal gt T dcg_body_terminal gt dcg_body_terminal gt dcg_terminals dcg_body_terminal gt 7 dcg_body_terminal gt dcg_body dcg_body_terminal gt dcg_nonterminal dcg_nonterminal gt Term callable_term Term dcg_terminals gt Term dcg_terminals gt Term dcg_terminals 4 2 DEFINITE CLAUSE GRAMMAR 221 4 2 3 DCG Expansion We can best see what the expansion process does by looking at the output of expand_term 2 for each DCG grammar non terminal Rules Rules are the starting point dcg_rule gt dcg_nonterminal P E dcg_terminals gt gt dcg_body dcg_rule gt dcg_nonterminal gt dcg_body The head of the clause which is generated for this rule is built from the non terminal on the left of the arrow This rule can be referenced on the right hand side of rules by using this non terminal expand_term a gt b T T a _542064 542032 b _542064 _ 542032 yes The terminals which can follow the non terminal on the left hand side of the arrow allow you to constrain the second list argumen
186. of 1 makes more sense to humans than calling it line 0 Examples See set_stream_position 2 Errors None See also set_stream_position 2 stream_property 2 4 1 210 stream_position_line_position 2 Synopsis stream_position_line_position Position Count Description This predicate succeeds if Position is a stream position term and Count is the offset from the beginning of the current line in characters Examples See set_stream_position 2 Errors None See also set_stream_position 2 stream_property 2 194 CHAPTER 4 BUILT IN PREDICATES 4 1 211 stream_property 1 Synopsis stream_property T Description Succeeds if the argument T is a valid stream property term Behaves as if it were defined as follows stream_property file_name _ stream_property mode _ stream_property input stream_property output stream_property alias _ stream_property position _ stream_property end_of_stream _ stream_property eof_action _ stream_property reposition _ stream_property type _ stream_property character_encoding _ Examples stream_property type nonsense yes Errors None See also stream_property 2 4 1 212 stream_property 2 Synopsis stream_property S T Description Succeeds if the stream S has property T This is the list of valid properties file_name F The atom that was used to open the stream was F See open 4 4 1 PREDICATES 195
187. of the list of numbers A and B If Low lt 0 lt High then we cannot say with 1 Alpha percent confidence that the two samples are different Examples Suppose we have measured the response times for a benchmark program on two different Call these response times T1 and T2 We can use unpaired_t_test 5 to calculate the 95 confidence interval for the mean difference T1i 186 181 176 149 184 190 158 139 175 148 152 111 141 153 190 157 131 149 135 132 T2 129 132 102 106 94 102 87 99 170 113 135 142 86 143 152 146 144 unpaired_t_test T1 T2 0 05 Low High Ti 186 181 176 149 184 190 158 139 175 148 152 111 141 153 190 157 131 149 135 132 T2 129 132 102 106 94 102 87 99 170 113 135 142 86 143 152 146 144 Low 18 142755 High 50 616069 yes The result tells us with 95 confidence that the mean response time for the second program is between 18 143 and 50 616 time units faster than the mean response time for the first program Errors domain_error non_empty_list Either the argument A or the argu ment B was the empty list domain_error not_less_than_zero Alpha The argument Alpha was less than 0 13 1 PREDICATES 337 domain_error not_greater_than_one Alpha The argument Alpha was greater than 1 instantiation_error At least one the arguments A B or Alpha was an uninstantiated variable type_error list L Either the argument A or the argume
188. olute_deviation 2 13 1 12 sample_arithmetic_mean 2 Synopsis sample_arithmetic_mean L M Description This predicates calculates the arithmetic mean M of a list of numbers L 13 1 PREDICATES 321 Examples sample_arithmetic_mean 1 2 3 4 5 6 7 8 9 10 M M 5 5 yes Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also None 13 1 13 sample_coefficient_of_variation 2 Synopsis sample_coefficient_of_variation L Result Description Result is the sample coefficient of variation of the list of numbers L Examples sample_coefficient_of_variation 1 1 1 COV COV 0 0 yes sample_coefficient_of_variation 1 2 3 COV COV 0 5 yes 322 CHAPTER 13 THE STATISTICS LIBRARY Errors domain_error non_empty_list The argument L was the empty list A instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also None 13 1 14 sample_geometric_mean 2 Synopsis sample_geometric_mean L M Description This predicates calculates the geometric mean M of a list of num
189. on 2 326 sample_quantile 3 326 sample_quantile 7 327 sample_semi_interquartile_range 2 329 sample_standard_deviation 2 330 sample_standard_deviation 3 331 sample_variance 2 332 sample_variance 3 332 seek 4 180 select 3 266 select 4 265 selectchk 3 267 INDEX selectchk 4 266 set_input 1 181 set_output 1 182 set_prolog_flag 2 183 set_stream_position 2 184 setof 3 186 shorter_list 2 268 sort 2 187 source_sink 1 188 spy 1 352 statistics 1 189 stream 1 190 stream_alias 2 191 stream_position_byte_count 2 192 stream_position_character_count 2 192 stream_position_line_count 2 193 stream_position_line_position 2 193 stream_property 1 194 stream_property 2 194 students_t_cdf 3 333 students_t_pdf 3 334 students_t_qauntile 3 335 sub_atom 5 196 subseq 3 268 subseq0 2 269 subseq1 2 270 subsumes_chk 2 198 subsumes_term 2 198 sumlist 2 271 system_error 0 199 term_expansion 2 201 throw 1 201 top_sort 3 252 trace 0 8 353 trim_blanks 2 308 true 0 202 unget_byte 1 202 unget_byte 2 203 unget_char 1 204 unget_char 2 204 unget_code 1 205 unget_code 2 206 unify_with_occurs_check 2 208 unpaired_t_test 5 336 var 1 210 version 0 217 vertices 2 253 warshall 2 253 well_formed_body_term 1 210 write 1 211 write 2 212 write_canonical 1 213 write_canonical 2 214 INDEX write_term 2 214 write_term 3 215 writeg 1 212 writeg 2 213 indicator 13 mode 2
190. one See also None 283 284 CHAPTER 9 THE ORDSET LIBRARY Chapter 10 The printtree library To use the predicates in this library you will need to load the printtree fasl file One way to do this is with the following call ensure_loaded runtime printtree 10 1 Predicates 10 1 1 print_tree 1 Synopsis print_tree Term Description Behaves as if it were defined as print_tree Term current_input Stream print_tree Stream Term Examples See print_tree 2 Errors None See also print_tree 2 285 286 CHAPTER 10 THE PRINTTREE LIBRARY 10 1 2 print_tree 2 Synopsis print_tree Stream Term Description Prints the argument Term as a tree on Stream Examples print_tree s np det the noun man vp v sees ered oes np vp om det noun v the man sees yes print_tree user_output 99 99 yes print_tree user_output 99 9 float AE ss PON 14397107288778001613 7 64 yes Errors None 10 1 PREDICATES 287 See also None 288 CHAPTER 10 THE PRINTTREE LIBRARY Chapter 11 The readin library To use the predicates in this library you will need to load the readin fasl file One way to do this is with the following call ensure_loaded runtime readin 11 1 Predicates 11 1 1 read_in 1 Synopsis read_in Words Description Behaves as if it were defined as read_in Words c
191. ook Examples See add_message_hook 1 Errors None See also add_message_hook 1 print_message 2 4 1 167 private_procedure 1 Synopsis private_procedure T Description Succeeds if the predicate indicator T identifies a private procedure which is equivalent to a static predicate This predicate behaves as if it was defined as private_procedure P procedure_property P static Examples private_procedure private_procedure 1 yes Errors See procedure_property 2 See also procedure_property 2 public_procedure 1 4 1 PREDICATES 159 4 1 168 procedure_property 2 Synopsis procedure_property I P Description Succeeds if I is a predicate indicator which identifies a compiled predicate and P static or I is a predicate indicator which identifies an interpreted predicate and P dynamic Examples assert foo yes procedure_property foo 0 P P dynamic yes procedure_property procedure_property 2 P P static yes Errors instantiation_error The argument I was not instantiated type_error predicate_indicator I The argument I was not a predi cate indicator See also procedure_property 2 4 1 169 prolog_lexical_digit 1 Synopsis prolog_lexical_digit Code Description Succeeds if the character code Code represents a numerical character that can be used to start a Prolog integer or floating point number 160 CHAPTER 4 BU
192. or_alias S The argument S was not a valid stream term or atom existence_error stream S The argument S did not identify an open stream See also at_end_of_stream 0 stream_alias 2 4 1 26 atom 1 Synopsis atom T Description Succeeds if T is an atom Examples atom atom yes atom atom atom no atom 99 no Errors None See also None 4 1 27 atom_chars 2 Synopsis atom_chars A L atom_chars A L 4 1 PREDICATES 47 Description Succeeds if the name of the atom A corresponds to the list of characters L Examples atom_chars foo C C f 0 0 yes atom_chars C Cc 2 yes atom_chars A a t o m A atom yes Errors instantiation_error Either both arguments were uninstantiated or A was uninstantiated and L was not ground type_error atom A The argument A was instantiated but it was not an atom type_error list L The argument L was instantiated but it was not a list type_error character E The argument L contained an element E which was not a character See also atom_codes 2 character 1 4 1 28 atom_codes 2 Synopsis atom_codes A L atom_codes A L Description Succeeds if the name of the atom A corresponds to the list of character codes L 48 CHAPTER 4 BUILT IN PREDICATES Examples atom_codes foo L L 102 111 111 yes atom_codes A 102 103 104
193. ors domain_error stream_or_alias S The argument Sis not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error One of the arguments S or C was not instantiated permission_error input stream S There is a lack of permission to read from stream S permission_error input binary_stream S The argument S refers to a binary stream type_error character C The argument C was instantiated but not a valid character See also character 1 4 1 225 unget_code 1 Synopsis unget_code C Description Behaves as if it were defined as follows unget_code Code current_input S unget_code S Code 206 CHAPTER 4 BUILT IN PREDICATES Examples See unget_code 2 Errors See unget_code 2 See also current_input 1 unget_code 2 4 1 226 unget_code 2 Synopsis unget_code S C Description Places a character code C into the text stream S so that it will be the next character code read from that stream Examples test_unget_code open test_file txt read Stream unget_code Stream 64 get_code Stream 64 close Stream Errors domain_error stream_or_alias S The argument S is not a valid stream term or stream alias existence_error stream S The stream S does not exist instantiation_error One of the arguments S or C was not instantiated permission_error input stream S There is a lack of permission to read from s
194. owing read This is an input stream The position of the stream is set to the beginning of the file write This is an output stream If the file does not exist then create it The position of the stream is set to the beginning of the file append This is an output stream If the file does not exist then create it The position of the stream is set to the end of the file The argument 0 is a list of terms Each element of this list must be one of the following alias A The atom A can be used instead of the stream term S to refer to this stream Two streams may not have the same alias In this case a permission error exception is thrown character_encoding ascii This is an ASCII encoded stream character_encoding latin_1 This is an Latin 1 ISO 8859 1 encoded stream character_encoding utf_8 This is an Unicode UTF 8 encoded stream 142 CHAPTER 4 BUILT IN PREDICATES character_encoding utf_16be This is an Unicode UTF 16BE encoded stream character_encoding utf_16le This is an Unicode UTF 16LE encoded stream character_encoding utf_32be This is an Unicode UTF 32BE encoded stream character_encoding utf_32le This is an Unicode UTF 32LE encoded stream eof_action error Upon reading past the end of a file throw a permission error exception eof _action eof_code Upon reading past the end of a file return an end of file code eof_action reset Upon reading past the end of a file reposition the stream s
195. parser that automatically caches input sequences and the corresponding parse information This cache eliminates recomputation when the input sequence is seen again e Unlike a DCG grammar a BUP grammar cannot handle empty pro ductions at this time It is an error for a BUP grammar to contain a cycle To create a parser the BUP compiler bup_compile 2 is given the name of a file containing a grammar and the name of a file where the Prolog clauses which implement the corresponding parser are to be written The user can then consult the Prolog clauses and use the bup_goal 4 predicate to parse The input to the compiler is in the form of Prolog terms with principle functor 2 The format is the same as that of a DCG with the exception that gt 2 is replaced by 2 Here is an example BUP grammar 237 238 CHAPTER 6 THE BUP LIBRARY s s NP VP np NP vp VP np np D N det D noun N vp vp V NP verb V np NP det d the the det d a a noun n cat cat noun n dog dog noun n mouse mouse verb v chases chases verb v scares scares If the above grammar was stored in the file grammar bup we could com pile load and use the grammar with the following ensure_loaded runtime bup yes bup_compile grammar bup grammar pl BUP compilation input file grammar bup output file grammar pl F
196. prematurely due to an exception being thrown we trace an exception event In total we can trace call exit redo fail and exception events e Trace output is extended to include amongst other things a global invocation count and a call depth count 342 CHAPTER 14 DEBUG e Trace events can be leashed When execution reaches a leashed event a trace output is generated as usual but instead of continuing straight on to the next event execution is paused and the user is prompted for a command which the debugger will execute before it continues This is similar to the step function of other programming language debuggers e Tracing can be turned off and at a later stage automatically turned on when control reaches predicates which have spypoints placed on them The debugger will then pause and await a command at every event connected to this predicate regardless of whether the event is leashed or not A spypoint is similar to the breakpoint function of other programming language debuggers In order to accomplish all this a degree of resource usage is required beyond that of the default interpreter e g local stack usage is increased greatly This should be borne in mind so as to avoid resource exhaustion when dealing with deeply nested calls or recursion 14 2 1 Starting the debugger The debugger is not a fundamental part of the system as the system can function quite happily without it To bring the debugger into pla
197. priority values has a higher precedence that is to say it binds more tightly A call of op 3 where Priority is 0 will remove the entry associated with AtomName and Associativity Associativity This argument is one of the following fx A one argument non associative prefix operator fy A one argument right associative prefix operator xfx A two argument non associative infix operator xfy A two argument right associative infix operator yfx A two argument left associative infix xf A one argument non associative postfix operator yf A one argument left associative postfix operator AtomName Depending on the number of arguments specified in Associativity the operator is either AtomName 1 or AtomName 2 To demonstrate how operators work let us take three functors 2 g 2 and h 1 Normally we would build a term from these like this f g 1 2 h 3 We can define the h 1 functor as a prefix operator op 0 fx h Priority of zero removes existing operator h 1 op 500 fx h and write the very same term like this f g 1 2 h 3 In a similar way we could have defined the functor as a postfix operator 16 CHAPTER 3 THE PROLOG LANGUAGE op 0 fx h Remove the prefix operator h 1 op 500 xf h which would allow us to write this 8 1 2 3 h The functor g 2 could be made infix op 0 xfy g op 600 xfy g enabling us to write f 1 g 2 3h The functor 2 could also be made infix op 0 xfy f op
198. qual Examples ord_seteq 1 2 3 1 1 2 3 yes ord_seteq 1 2 3 1 2 3 4 no Errors None See also None 9 1 13 ord_subset 2 Synopsis ord_subset 01 02 Description Succeeds if the ordered set 01 is a subset of the ordered set 02 9 1 PREDICATES 281 Examples ord_subset 2 3 1 2 3 yes ord_subset 1 2 3 2 3 no Errors None See also None 9 1 14 ord_subtract 3 Synopsis ord_subtract 01 02 703 Description Succeeds if the ordered set 03 is the difference between the ordered sets 01 and 02 Examples ord_subtract 1 2 3 2 3 0 0 1 yes ord_subtract 1 2 3 4 5 1 2 3 yes Errors None See also ord_symdiff 3 9 1 15 ord_symdiff 3 Synopsis ord_symdiff 01 02 703 282 CHAPTER 9 THE ORDSET LIBRARY Description Succeeds if the ordered set 03 is the symmetric difference between the ordered sets 01 and 02 Examples ord_symdiff 1 2 3 2 3 0 0 1 yes ord_symdiff 2 3 1 2 3 0 0 1 yes ord_subtract 2 3 1 2 3 0 O yes Errors None See also ord_subtract 3 9 1 16 ord_union 3 Synopsis ord_union 01 02 03 Description Succeeds if the ordered set 03 is the union of the ordered sets 01 and 02 Examples ord_union 1 2 3 2 3 0 0 1 2 3 yes 9 1 PREDICATES Errors N
199. r of bytes of the constants section that is currently unused 190 CHAPTER 4 BUILT IN PREDICATES strings_used B B is the number of bytes of the strings section that is cur rently being used strings_free B B is the number of bytes of the strings section that is cur rently unused functors_used B B is the number of bytes of the functors section that is currently being used functors_free B B is the number of bytes of the functors section that is currently unused clause_store_gc_count C C is the number of times the clause store has been garbage collected data_section_gc_count C C is the number of times the local and global stacks have been garbage collected Examples statistics Stats Stats wall_clock 1379264168244 global_stack_used 515952 global stack_free 83370112 local_stack_used 9088 local_stack_free 67099776 trail_used 488 trail_free 67108376 clause_store_used 61376 clause_store_free 2035776 code_used 217456 code_free 44688 constants_used 37008 constants_free 225136 strings_used 19369 strings_free 111703 functors_used 27168 functors_free 103896 clause_store_gc_count 0 data_section_gc_count 0 yes Errors None See also None 4 1 205 stream 1 Synopsis stream T 4 1 PREDICATES 191 Description Succeeds if T is either a stream term or a variable Examples stream_alias user_input S stream S S stream 0 yes stream V V _525152
200. r stream T The argument T identified a nonexistent stream instantiation_error The argument T was not instantiated permission_error output stream T There was no permission to use the argument T as an output stream See also None 4 1 199 set_prolog flag 2 Synopsis set_prolog flag Flag Term Description Sets the value of the predefined Prolog flag Flag to Term 184 CHAPTER 4 BUILT IN PREDICATES Examples current_prolog_flag F V F debug V off yes set_prolog_flag debug on yes current_prolog_flag debug V V on yes set_prolog flag debug off yes current_prolog_flag debug V V off yes Errors domain_error flag_value Term The argument Term was not a valid flag value for the argument Flag domain_error prolog_flag Flag The argument Flag was not a valid prolog flag instantiation_error One of the arguments Flag or Term was not instan tiated permission_error modify flag Flag There was no permission to mod ify the flag Flag type_error atom Flag The argument Flag was not an atom See also current_prolog_flag 2 4 1 200 set_stream_position 2 Synopsis set_stream_position Stream Position 4 1 PREDICATES 185 Description Sets the position of the stream Stream to the position Position The argu ment Position is an internal structure that should be configured with the following predicates stream_position
201. r to the well known Context Free Grammar CFG DM93 Just like a CFG a DCG describes a language using rules terminals and non terminals However where the right hand side of a CFG rule is defined as a sequence of terminals and non terminals a DCG s right hand side can in addition contain Prolog queries and certain extra grammatical operators such as 0 or gt 2 which behave in the same way in grammar rules as their extra logical namesakes do in Prolog goals Also the left hand side of a CFG rule is constrained to be a single non terminal but a DCG rule can have an optional list of terminals following the non terminal on its left hand side When input as a read term a DCG rule is automatically expanded into a Prolog clause by expand_term 2 This gives the programmer a convenient language to define language acceptors and generators 218 CHAPTER 4 BUILT IN PREDICATES 4 2 1 Motivation Consider the following clause det 2 which succeeds if its first argument is a list which begins with the symbol the an English language determiner and the second argument is the first argument minus this determiner prefix det the Rest Rest Consider also these clauses which deal with some English nouns in the same way noun cat Rest Rest noun dog Rest Rest If we take the conjunction of det 2 and noun 2 and feed the second argument of det 2 into the first argument of noun 2 then we would have the body of a c
202. rator so the argument does not need parentheses Examples debugging Debugging is off Tracing is off Spying on the following list of predicates fact 2 yes nospy fact 2 yes debugging Debugging is off Tracing is off Spying on the following list of predicates yes Errors See remove_spypoint 1 See also debugging 0 remove_spypoint 1 14 3 7 nospyal1 0 Synopsis nospyall Description Removes any spypoints on any predicates existing or not 14 3 DEBUG PREDICATES Examples debugging Debugging is on Tracing is off Spying on the following list of predicates fact 2 yes nospyall yes debugging Debugging is on Tracing is off Spying on the following list of predicates yes Errors None See also debugging 0 remove_spypoint 1 nospy 1 14 3 8 notrace 0 Synopsis notrace Description Equivalent to nodebug 0 Examples See nodebug 0 Errors None See also nodebug 0 351 302 CHAPTER 14 DEBUG 14 3 9 remove_spypoint 1 Synopsis remove_spypoint PI Description Removes the spypoint from the predicate identified by the predicate indicator PI It is possible to remove a nonexistent spypoint It is even possible to remove the spypoint of a nonexistent predicate The predicates that have spypoints can be queried with the predicate debugging 0 Examples debugging Debugging is on Tracing is o
203. re the first element of the pair is a vertex and the second element is a list of immediate neighbour vertices of the first element The list of pairs is sorted see keysort 2 as is the list of neighbours see sort 2 Example a b b a c c a The reason for the two representations is that they are each suited for dif ferent uses Some algorithms are easier to express if the S representation is used and graphs are easier for a human to give as input in P representation 7 1 Predicates 7 1 1 compose 3 Synopsis compose G1 G2 G3 Description Succeeds if the graph G3 is the composition of the graphs G1 and G2 All graphs are in S representation 247 248 CHAPTER 7 THE GRAPHS LIBRARY Examples p_to_s_graph u v S1 p_to_s_graph u v v w S2 compose S1 S2 3 81 u v v 11 S2 u v v w w 7 S3 u w v 7 w yes Errors None See also None 7 1 2 p_member 3 Synopsis p_member V1 V2 G Description Succeeds if there is an edge from vertex V1 to vertex V2 in the graph G which is given in P representation Examples p_member V1 V2 a b b c Vi a V2 b b Vi b V2 c no Errors None 7 1 PREDICATES 249 See also s_member 3 7 1 3 p_to_s_graph 2 Synopsis p_to_s_graph P S Description This predicate takes a graph P in P representation and unifies S with the equivalent S representation graph Examples
204. redicate behaves as if it were defined as follows between Low High Low Low lt High between Low High Value Low lt High 52 CHAPTER 4 BUILT IN PREDICATES NextLow is Low 1 between NextLow High Value Examples between 1 2 X print X nl fail print done nl 1 2 done X _25248 yes Errors Since the arguments are evaluated errors may be raised by eval 2 See also None 4 1 34 bagof 3 Synopsis bagof Template Goal Bag Description Bag is a list representing a multiset of instances of Template which satisfy Goal Should Goal be unsatisfiable bagof 3 fails For this to be useful you will want at least one uninstantiated variable in Template to be free in Goal Those uninstantiated variables which are part of Goal but not part of Template are considered to be universally quantified and thus may give rise to several solutions for the bagof 3 call As an example of this the following shows a bagof 3 query giving 3 solutions yes bagof X member X Y 1 2 3 4 5 6 L X _521856 Y 2 L 1 Ps Il _521856 Y 4 3 EA ll 4 1 PREDICATES 53 X _521856 Y 6 L 5 no It is possible to avoid these extra solutions by existentially quantifying these uninstantiated free variables that are in Goal but not in Template Variables are existentially quantified with the 2 operator Here we alter the previous example a
205. rees of freedom Examples students_t_pdf 0 1 Answer Answer 0 318310 yes Errors domain_error not_less_than_one N The argument N was less than 1 instantiation_error One the arguments X or N was an uninstantiated vari able 13 1 PREDICATES 335 type_error integer N The argument N did not evaluate to an integer Also as the arguments X and N are evaluated errors may be thrown by eval 2 See also None 13 1 29 students_t_quantile 3 Synopsis students_t_quantile X N Answer Description Answer is the X quantile 0 lt X X lt 1 of the Student s t distribution with N degrees of freedom Examples students_t_quantile 0 9 9 Answer Answer 1 383027 yes Errors domain_error not_less_than_one N The argument N was less than 1 domain_error not_less_than_zero X The argument X was less than 0 domain_error not_greater_than_one X The argument X was greater than 1 instantiation_error Fither the argument X or the argument N was an uninstantiated variable type_error integer N The argument N did not evaluate to an integer Also as the arguments X and N are evaluated errors may be thrown by eval 2 See also None 336 CHAPTER 13 THE STATISTICS LIBRARY 13 1 30 unpaired_t_test 5 Synopsis unpaired_t_test A B Alpha Low High Description The interval Low High is the 1 Alpha percent confidence interval of the difference of the means
206. rors None See also None 4 1 38 cal1 1 Synopsis call T Description Invokes the interpreter on the term T Examples call true yes call fail no 56 CHAPTER 4 BUILT IN PREDICATES call call print call n1 call yes Errors instantiation_error The argument T was not instantiated type_error callable T The argument T was not a callable term See also callable_term 1 4 1 39 cal1 3 Synopsis call T1 T2 T3 Description Calls the term formed by taking the callable term T1 and adding the terms T2 and T3 as the new last two arguments So if T1 is a term with functor F and arity N then the new term would have the predicate indicator F N 2 This predicate is used in code generated by Definite Clause Grammar expansion it behaves as if defined as follows call Pred Argi Arg2 Pred Functor Args append Args Argl Arg2 NewArgs New_pred Functor NewArgs call New_pred Examples expand_term a gt call b T T a _544096 _544064 call b _544096 _544064 yes Errors instantiation_error The argument T1 was not instantiated See also eall 1 4 1 PREDICATES 57 4 1 40 callable_term 1 Synopsis callable_term T Description Succeeds if T is a callable term This definition of callable term is i all atoms are callable terms and ii all compound terms are callable terms Examples
207. rors None See also absolute_file_name 3 4 1 PREDICATES 189 4 1 204 statistics 1 Synopsis statistics S Description Succeeds if S is a key value list describing the state of the Prolog system There is one key value pair for each monitored part of the system The following is a description of all the keys and their values wall_clock T T is the number of milliseconds since midnight before January 1 1970 global_stack_used B B is the number of bytes of the global stack that is currently being used global_stack_free B B is the number of bytes of the global stack that is currently unused local_stack_used B B is the number of bytes of the local stack that is currently being used local_stack_free B B is the number of bytes of the local stack that is currently unused trail_used B B is the number of bytes of the trail that is currently being used trail_free B B is the number of bytes of the trail that is currently unused clause_store_used B B is the number of bytes of the clause store that is currently being used clause_store_free B B is the number of bytes of the clause store that is currently unused code_used B B is the number of bytes of the code section that is currently being used code_free B B is the number of bytes of the code section that is currently unused constants_used B B is the number of bytes of the constants section that is currently being used constants_free B B is the numbe
208. s current_message_hook F F foo yes del_message_hook foo yes current_message_hook F no Errors None 72 CHAPTER 4 BUILT IN PREDICATES See also add_message_hook 1 del_message_hook 1 4 1 61 current_op 3 Synopsis current_op P S 0 Description Succeeds if the operator table contains an entry for the operator O with precedence P and specification S The operator table is updated with op 3 Examples findall P S current_op P S L _522496 _523360 500 yfx 200 fy P S L yes Errors domain_error operator_priority P The argument P was neither unin stantiated nor an integer between 0 and 1200 inclusive domain_error operator_specifier S The argument S was neither unin stantiated nor an operator specifier type_error atom P The argument O was neither uninstantiated nor an atom See also op 3 4 1 62 current_output 1 Synopsis current_output T Description Succeeds if T is the current output stream 4 1 PREDICATES 73 Examples current_output S S stream 1 yes Errors type_error stream T The argument T was neither uninstantiated nor a stream term See also set_output 1 4 1 63 current_portray 1 Synopsis current_portray F Description Succeeds if at some point add_portray F has been called to add the pro cedure specified by the predicate indicator F 2
209. s follows e Variables precede floating point numbers e Floating point numbers precede integers e Integers precede atoms e Atoms precede compound terms 200 CHAPTER 4 BUILT IN PREDICATES e Two variables are ordered according to their memory addresses e Two numbers are ordered arithmetically e Two atoms are ordered according to the lexicographical ordering of their names The null atom is the least atom e Two compound terms are ordered according to their arity Two com pound terms of the same arity are ordered according to the lexico graphical ordering of their principle functor names Two compound terms with the same arity and principle functor are ordered according to the term ordering of the first argument that they do not share With this ordering in mind we can say that a term is less than equal to or greater than another term These relations are offered via the following binary predicates L R L equal to R L R L not equal to R L lt R L less than R L lt R L less than or equal to R L gt R L greater than R L gt R L greater than or equal to R Examples a lt b yes 3 3 0 no 3 3 yes Errors Errors are not thrown by these predicates See also compare 3 setof 3 sort 2 4 1 PREDICATES 201 4 1 218 term_expansion 2 Synopsis term_expansion T1 T2 Description Succeeds if there is a term expansion hook which succeeds with the s
210. st chars_to_atom Codes Input InputRest Description Succeeds if Codes is the difference between the lists Input and InputRest and each element of Codes represents an alphabetic letter This predicate behaves as if it were defined as follows chars_to_atom L Ls gt L is_letter L chars_to_atom Ls chars_to_atom gt Examples chars_to_atom foo A B A 102 111 111 _554608 B _554608 yes chars_to_atom Codes foo 123 Rest Codes 102 111 111 Rest 32 49 50 51 yes Errors See is_letter 1 12 1 PREDICATES 295 See also is_letter 1 12 1 3 chars_to_integer 3 Synopsis chars_to_integer Codes Input InputRest chars_to_integer Codes Input InputRest Description Succeeds if Codes is the difference between the lists Input and InputRest and each element of Codes represents a decimal digit This predicate behaves as if it were defined as follows chars_to_integer D Ds gt D is_digit D chars_to_integer Ds chars_to_integer gt Examples chars_to_integer 123 A B A 49 50 51 _555088 B _555088 yes chars_to_integer Codes 123 foo Rest Codes 49 50 51 Rest 32 102 111 111 yes Errors See is_digit 1 See also is_digit 1 296 CHAPTER 12 THE READSENT LIBRARY 12 1 4 chars_to_string 3 Synopsis chars_to_string Codes Input InputRest chars_to_string Co
211. stream S There was no permission to read from stream S syntax_error badly_formed_list A list was not ended with a close bracket syntax_error bracket_expected_in_arguments There was a missing bracket in the input term syntax_error cannot_start_an_expression Token The token Token started an expression 176 CHAPTER 4 BUILT IN PREDICATES syntax_error expression_expected There was a missing expression syntax_error follows_expression Token The token Token immediately follows an expression syntax_error not_all_read Not all of the term was read at the end if the input syntax_error operator_expected_after_expression Two adjacent terms were read syntax_error prefix_operator_precedence Op Prec The operator Op with precedence Prec immediately followed a prefix operator syntax_error token_or_operator_expected Token The token Token was expected but not read type_error list 0 The argument 0 was not a list See also None 4 1 191 reconsult 1 Synopsis reconsult F Description Opens the file specified by F and loads the terms found in the file into the clause store Note that since reconsult uses open 4 the argument F is in turn passed to absolute_file_name 2 for translation Note that this is a reconsult and not a consult Should you reconsult the same file twice then you will have only one copy of all read terms in the clause store Examples reconsult slask foo yes
212. t expand_term a b gt c T T a _543408 _543376 c _543408 _544608 _543376 b _544608 yes expand_term a b c gt d T T a _544032 _544000 d _544032 545232 _544000 b c _545232 yes expand_term a b gt T assert T T a _546704 _546672 _546704 _547808 _546672 bl_547808 a A B A _520960 B bl_520960 yes Disjunctions A body can contain a disjunction which is essentially a grammatical alter native 222 CHAPTER 4 BUILT IN PREDICATES dcg_body gt dcg_body_disjunction dcg_body_disjunction gt dcg_body_conditional dcg_body dcg_body_disjunction gt dcg_body_conditional dcg_body dcg_body_disjunction gt dcg_body_conjunction dcg_body dcg_body_disjunction gt dcg_body_conjunction dcg_body dcg_body_disjunction gt dcg_body_conjunction These five disjunction rules are in fact only three rules because the first two rules are exactly the same and the the third and fourth rules are exactly the same The reason for this is that the symbol is never a functor returned by read_term 3 it is only treated as a synonym for which can be seen from this example read X a b X aj b yes The expansion is straightforward expand_term a gt b c T T a _554640 _554608 b _554640 _554608 c _554640 _554608 yes
213. t 2 4 1 122 keysort 2 Synopsis keysort T1 T2 4 1 PREDICATES 123 Description Succeeds if T1 is a list of key pair terms and T2 has all of the members of Ti in an ascending order the ordering relation on key pairs being the predicate 0 lt 2 applied to the first elements of the pairs and T1 and T2 have equal lengths i e no merging takes place Examples keysort 2 a 1 b 3 c 1 b Result Result 1 b 1 b 2 a 3 c yes Errors instantiation_error The argument T1 was not instantiated type_error list T1 The argument T1 was not a list type_error key_pair T1 The argument T1 was not a list of key pairs See also key_pair 1 4 1 123 length 2 Synopsis length L N Description Succeeds if the length of the list L is N Examples length L 3 L _552528 _552576 _552624 yes length 1 2 N N 2 yes 124 CHAPTER 4 BUILT IN PREDICATES Errors None See also None 4 1 124 listing 0 Synopsis listing Description Displays the clauses connected with all of the dynamic predicates in the clause store This predicate behaves as if it were defined as follows listing current_predicate P listing P fail listing Examples None Errors None See also current_predicate 1 listing 1 4 1 125 listing 1 Synopsis listing Pred 4 1 PREDICATES 125 Description This predicate behaves as if it were defined
214. t_byte Stream 16 be get_byte Stream 16 ef skip_to_end_of_binary_file Stream close Stream Errors instantiation_error The argument S was not instantiated type_error in_byte B The argument B was instantiated but not a valid input byte permission_error input past_end_of_stream S Tried to read past the end of the stream permission_error input stream S There is a lack of permission to read from stream S permission_error input text_stream S The argument S refers to a text stream existence_error stream S The stream S does not exist domain_error stream_or_alias S The argument S is not a valid stream term or stream alias See also in_byte 1 unget_byte 2 4 1 106 get_char 1 Synopsis get_char C Description Behaves as if it were defined as follows get_char Char current_input S get_char S Char 4 1 PREDICATES 113 Examples See get_char 2 Errors See get_char 2 See also current_input 1 get_char 2 4 1 107 get_char 2 Synopsis get_char S C Description Reads a character C from the text stream S Examples test_get_char open test_file txt read Stream get_char Stream d get_char Stream e get_char Stream a get_char Stream d skip_to_end_of_text_file Stream close Stream Errors instantiation_error The argument S was not instantiated type_error in_character C The argument C was instantiated but not a vali
215. tarts a comment e One of the following solo characters or e One of the following two character sequences or e Any sequence of characters within single quotes e g example If you want to have a single quote within the single quotes you must prefix it with another single quote e g example s e If the Prolog flag double_quotes is set to atom then any sequence of characters within double quotes e g example If you want to have a double quote within the double quotes you must prefix it with another double quote e g he said no See the documentation for the built in predicates current_prolog_flag 2 and set_prolog_flag 2 The character sequences contained within single or double quotes may con tain escape codes depending on the value of the Prolog flag char_escapes See the documentation for the built in predicates current_prolog_flag 2 and set_prolog_flag 2 When permitted set to on the following list of escape codes can be used Note that any characters given in lower case can also be given in upper case Some of the definitions use the term whitespace which is defined later a Replace with Unicode code 7 bell b Replace with Unicode code 8 backspace d Replace with Unicode code 127 delete e Replace with Unicode code 27 escape f Replace with Unicode code 12 form feed 3 1 SYNTAX 11 n Replace with Unicode code 10 newline r Replace with Unicode code 13 return
216. te_term_options 354 2 gt 2 18 debug 8 354 gt gt gt 2 18 discontiguous_clauses_warnings 228 gt 2 18 double_quotes 10 14 228 2 gt 2 18 floating_point_output_format 229 2 7 2 18 floating_point_output_precision 229 2 2 18 floating_point_precision 229 gt 1 18 integer_rounding_function 230 gt 2 18 max_arity 230 P3272 18 362 INDEX 7 2 18 2 7 2 18 2 18 gt 2 18 2 18 2 lt gt 2 18 27 gt 1 18 gt 0 lt gt 2 18 gt 0 lt gt 2 18 gt 0 gt gt 2 18 7 gt 2 18 2 2 18 1 18 7 1 18 NAL 2 18 2 18 AN gt 2 18 2 gt gt 2 18 2 gt gt 2 18 2 gt gt gt 2 18 2 lt gt 2 18 2 lt lt gt 2 18 discontiguous 1 18 div 2 18 dynamic 1 18 ensure_loaded 1 18 include 1 18 initialization 1 18 is 2 18 mod 2 18 multifile 1 18 rem 2 18 associativity 15 fixity 15 infix 15 postfix 15 precedence 15 prefix 15 priority 15 predicate gt 1 gt 0 78 2 65 2 gt gt 2 117 2 gt 2 13 90 gt 2 88 lt gt 2 39 2 gt 2 207 gt 2 209 gt 2 39 lt 2 39 gt 2 199 7 2 39 gt 2 39 363 gt gt 2 39 gt 0 lt gt 2 199 gt 0 lt gt 2 199 gt 0 gt gt 2 199 gt 0 gt gt 2 199 20 3 55 2 2 99 47 1 134 2 207 AM gt 2 199 abolish 1 21 abort 0 7 22 absolute_file_name 2 23 absolute_file_name 3 23 add_file_searc
217. ter is useful from a computational point of view it gives us no useful information when debugging What would help us is a trace of the interesting events which occur during execution 339 340 CHAPTER 14 DEBUG An obvious step towards this goal could be an interpreter which traced any attempt to call a goal We achieve this by augmenting demo 1 with some output predicates and we call the result trace1 1 tracel true trace1 G1 G2 trace1 G1 trace1 G2 trace1 G1 G2 trace1 G1 trace1 G2 tracel G write call tab 1 write G nl clause G C trace1 C When we feed the goal a to trace1 1 we get the following output tracel a calla call b call c call d yes This trace lets us see the Prolog interpreter in action but since we do not see what goals succeed and what goals fail the trace can be difficult to use for all but the smallest programs Another simple augmentation this time of trace1 1 will give us a trace upon a successful exit trace2 true trace2 G1 G2 trace2 G1 trace2 G2 trace2 G1 G2 trace2 G1 trace2 G2 trace2 G write call tab 1 write G nl clause G C trace2 C write exit tab 1 write G nl When we feed the goal a to trace2 1 we get the following output trace2 a call call exit call call exit 9 oaada s r mp exit yes From a lack of an exit trace for c we see that the goal c doesn
218. tes 9 1 1 list_to_ord_set 2 Synopsis list_to_ord_set L 0 Description This predicate converts the list L into an ordered set O This is equivalent to a call of sort L 0 Examples list_to_ord_set 3 3 2 2 1 1 0 D 1 2 3 yes 273 274 CHAPTER 9 THE ORDSET LIBRARY Errors None See also sort 2 9 1 2 ord_all_nonempty_subsets 2 Synopsis ord_all_nonempty_subsets 01 702 Description This predicate behaves as if it were defined as ord_all_nonempty_subsets 01 02 ord_powerset 01 P ord_subtract P 02 Examples ord_powerset 1 2 3 0 D 0 11 1 21 1 2 3 1 31 121 2 3 31 yes ord_all_nonempty_subsets 1 2 3 0 O 11 1 21 1 2 31 11 31 2 1 2 3 1 31 yes Errors None See also ord_powerset 2 ord_subtract 3 9 1 3 ord_all_subsets 2 Synopsis ord_all_subsets 01 02 9 1 PREDICATES 275 Description This predicate behaves as if it were defined as ord_allsubsets 01 02 ord_powerset 01 02 Examples See ord_powerset 2 Errors None See also ord_all_subsets 3 ord_powerset 2 9 1 4 ord_all_subsets 3 Synopsis ord_all_subsets 01 N 02 Description This predicate succeeds if 02 is the ordered set of all subsets of the ordered set 01 which are of cardinality N Examples ord_all_subsets 1 2 3 2 0 0 1 2 1 31 2 311 yes ord_all_subsets 1 2 3
219. the directory D Examples current_file_search_path A D A prolog D home bwat BarrysProlog A misc D prolog misc A runtime D prolog bin runtime yes Errors None See also add_file_search_path 2 del_file_search_path 2 70 CHAPTER 4 BUILT IN PREDICATES 4 1 58 current_generate_message 1 Synopsis current_generate_message 7 F Description Succeeds if at some point add_generate_message F has been called to add the procedure specified by the predicate indicator F 2 Examples current_generate_message F no add _generate_message foo yes current_generate_message F F foo yes del_generate_message foo yes current_generate_message F no Errors None See also add_generate_message 1 del_generate_message 1 4 1 59 current_input 1 Synopsis current_input T Description Succeeds if T is the current input stream 4 1 PREDICATES 71 Examples current_input S S stream 0 yes Errors domain_error stream T The argument T was neither uninstantiated nor a stream term See also set_input 1 4 1 60 current_message_hook 1 Synopsis current_message_hook F Description Succeeds if at some point add_message_hook F has been called to add the procedure specified by the predicate indicator F 3 Examples current_message_hook F no add_message_hook foo ye
220. the heap global stack The second argument is a dummy variable error resource_error local_stack _ There was no room left on the local stack The second argument is a dummy variable error resource_error pdl _ There was no room left on the PDL Push Down List The second argument is a dummy variable error resource_error strings _ There was no room left in the strings table The second argument is a dummy variable error resource_error trail _ There was no room left on the trail The second argument is a dummy variable error syntax_error M syntax_error G A B M C The goal G caused a syntax error in the file named A at position B The term M is a de scriptive message and C is the list of remaining input tokens 20 CHAPTER 3 THE PROLOG LANGUAGE error type_error A B type_error G N A B Argument number N of the goal G was the term B which was not of type A Chapter 4 Built in Predicates 4 1 Predicates 4 1 1 abolish 1 Synopsis abolish PI Description Removes the predicate identified by the predicate indicator PI from the clause store if it is dynamic When you compile a predicate it becomes static and cannot be abolished Examples assert foo yes foo yes abolish foo 0 yes foo ERROR Error class existence error Goal in error foo The predicate foo 0 does not exist Errors instantiation_error PI must be ground 21 22 CHAPTER 4 BUILT IN
221. ther or is seen The remaining codes up to and including the newline code are then consumed This predicate behaves as if it were defined as follows read_sent Stream Words read_until Stream is_newline Newline read_until Stream Newline _ y 306 CHAPTER 12 THE READSENT LIBRARY chars_to_words Chars Words 1 Examples current_input S read_sent S Words This is 1 sentence S stream 0 Words atom this atom is integer 1 atom sentence yes Errors See read_until 3 See also is_newline 1 read_sentence 1 read_until 3 12 1 21 read_sentence 1 Synopsis read_sentence Words Description Behaves as if it were defined as read_sentence Words current_input Stream read_sent Stream Words Examples See read_sent 2 Errors See read_sent 2 See also read_sent 2 12 1 PREDICATES 12 1 22 read_sentence 2 Synopsis read_sentence Stream Words Description Behaves as if it were defined as read_sentence Stream Words read_sent Stream Words Examples See read_sent 2 Errors See read_sent 2 See also read_sent 2 12 1 23 read_until 2 Synopsis read_until Delimiters Codes Description Behaves as if it were defined as read_until Delimiters Codes current_input Stream read_until Stream Delimiters Codes Examples See read_until 3 Errors See read_until 3 307
222. tified by the predicate indicator A 2 as a term expansion hook A term expansion hook is a predicate with arity 2 the first argument being the input term and the second argument being the expan sion of the input term When a term is read by consult 1 reconsult 1 or the top level loop then that term is given to each term expansion hook one at a time in the order they were registered with add_term_expansion 1 If one of the hooks succeeds then the term which was read is discarded and its expansion is used instead If none of the hooks succeed then the process just continues with the input term The term expansion phase occurs before the DCG expansion phase The registration of term expansion hooks which are already registered has no effect Examples assert foo print foo nl yes assert goo_not_foo print goo nl yes assert my_expander foo goo_not_foo yes foo foo yes add_term_expansion my_expander yes foo goo yes del_term_expansion my_expander yes foo foo yes Errors instantiation_error The argument A was not instantiated type_error atom A The argument A was not an atom See also current_term_expansion 1 del_term_expansion 1 expand_term 2 term_expansion 2 4 1 PREDICATES 37 4 1 14 append 3 Synopsis append T1 T2 T3 Description Succeeds if all of the arguments are lists and T3 is equal to the concatenat
223. tile_range L InterQuartileRange Result is InterQuartileRange 2 330 CHAPTER 13 THE STATISTICS LIBRARY Examples sample_semi_interquartile_range 1 2 3 4 5 6 7 8 R R 2 0 yes Errors domain_error non_empty_list The argument L was the empty list Cll instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_interquartile_range 2 13 1 23 sample_standard_deviation 2 Synopsis sample_standard_deviation L Result Description Result is the sample standard deviation of the list of numbers L Examples sample_standard_deviation 1 1 1 D D 0 0 yes sample_standard_deviation 1 2 3 D D 1 0 yes 13 1 PREDICATES 331 Errors domain_error non_empty_list The argument L was the empty list instantiation_error The argument L was an uninstantiated variable type_error list L The argument L was not a list Also as the members of the argument L are evaluated errors may be thrown by eval 2 See also sample_standard_deviation 3 13 1 24 sample_standard_deviation 3 Synopsis sample_standard_deviation L M Result Description Result is the sample standard deviation of the list of numbers L which has an arithmetic mean of M This predicate is provided for the cases where the me
224. tion An event for which we configure the debugger to stop is said to be leashed If Mode is the empty list then no events are leashed Otherwise if Mode is a list of symbols where each symbol is one of call exit redo fail or exception then the corresponding event is leashed A more user friendly mnemonic interface is offered where Mode can be one of atoms all tight half or off These modes are defined as follows all Equivalent to leash call exit redo fail exception 14 3 DEBUG PREDICATES 349 tight Equivalent to leash call redo fail half Equivalent to leash call redo off Equivalent to leash Examples leash all yes Errors domain_error leash_mode M Either the argument Mode was a list but contained an element M that was not a trace event symbol or the ar gument Mode was the symbol M which is not a valid port list mnemonic symbol instantiation_error The argument Mode was not instantiated See also None 14 3 5 nodebug 0 Synopsis nodebug Description Sets both of the flags debug and trace to the value off Examples nodebug yes debugging Debugging is off Tracing is off Spying on the following list of predicates fact 2 yes Errors None 350 CHAPTER 14 DEBUG See also debug 0 notrace 0 trace 0 14 3 6 nospy 1 Synopsis nospy PI Description Equivalent to remove_spypoint PI This predicate is defined as a prefix ope
225. tion has no effect The options extensions E and file_type T may conflict with each other and with multiples of themselves file_errors E Here E must be one of the following error Any errors encountered will lead to an exception being thrown fail Any errors encountered will lead to the failure of the call to absolute_file_name 3 file_type T This option either specifies that we are dealing with a direc tory and not a normal file or it is a shorthand for commonly used file extensions which could be defined with the option extensions E The options extensions E and file_type T may conflict with each other and with multiples of themselves The argument T must be one of the following text Equivalent to no file extension prolog Equivalent to extensions fasl pl fasl Equivalent to extensions fasl directory This file type is the only way to tell absolute_file_name 3 that we are dealing with a directory and not a normal file ignore_underscores I The translation process can be instructed to ignore underscores if it will lead to a successful translation Here I must be one of the following 4 1 PREDICATES 25 true Any underscores in RF may be removed when translating to AF false Underscores cannot be removed from RF solutions S The determinicity of absolute_file_name 3 is specified by this option Here S must be one of the following first Make absolute_file_name 3 deterministic i e
226. to avoid recomputation in subsequent parses You may wish to use retractal1 1 to remove this predicate and flush the cache Examples Here we assume that we have compiled the file grammar bup defined above with the option cache_goals on bup_goal s A the cat chases the mouse A s mp d the n cat vp v chases np d the n mouse yes listing bup_wf_goal 4 bup_wf_goal noun In cat cat chases the mouse chases the mouse bup_wf_goal noun n mouse mouse bup_wf_goal np np d the n mouse the mouse bup_wf_goal vp vp v chases np d the n mouse 246 CHAPTER 6 THE BUP LIBRARY chases the mouse bup_wf_goal s s mp d the n cat vp v chases np d the n mouse the cat chases the mouse Js yes Errors None See also bup_compile 3 retractal1 1 Chapter 7 The graphs library The predicates in this library are intended to help the programmer implement graph theoretical algorithms To use the predicates in this library you will need to load the graphs fas1 file One way to do this is with the following call ensure_loaded runtime graphs In this library two representations of graphs are used e The P representation which is a list of pairs where each element in the pair is a single vertex Example a b b c b a c al e The S representation which is a list of pairs whe
227. tput 1 write_term 3 4 1 240 write_term 3 Synopsis write_term S T 0 Description Writes the term T to the stream S in accordance with the elements of the list of options O The list of valid options is ignore_ops true All prefix infix and postfix operators are written in so called functional notation whereby the principle functor precedes a list of arguments which is contained in brackets Lists are written in terms of 2 ignore_ops false Any prefix infix or postfix operator see current _op 3 is written in accordance with its fixity and precedence numbervars true All terms of the form VAR N where N is a number are output as variables See numbervars 3 numbervars false All terms of the form VAR 1 are not given special treatment portray true Portray hooks can override the writing of terms See add_portray 1 portray false No portray hooks are called 216 CHAPTER 4 BUILT IN PREDICATES quoted true All atoms are written using their names but any names that could not be recognised by read_term 3 will be quoted quoted false All atoms are written using their names there is not auto matic quoting If two conflicting options are given in the list that is two options with the same principle functor then the last of the two takes precedence The default set of options is ignore_ops false numbervars false portray false quoted false Any option passed in the argument O
228. tracing suppose we had defined fact 2 as follows fact N F N lt 1 F 1 fact N F Mis N 1 fact M E F is NxE 344 CHAPTER 14 DEBUG If we wanted to trace the execution of fact 2 X with no user interaction we could perform the following sequence of actions 1 Make sure no events are leashed to remove any need for input from the user 2 Turn on debugging and tracing We ll assume the debugger is actually loaded 3 Give the query as we normally would do And we do it just like this leash off yes trace yes fact 2 X 0 O call dynamic fact 2 _195168 1 1 call static 2 lt 1 1 1 fail static 2 lt 1 2 1 call static _316624 is 2 1 2 1 exit static 1 is 2 1 3 1 call dynamic fact 1 _316784 4 2 call static 1 lt 1 4 2 exit static 1 lt 1 5 2 call static _316784 1 5 2 exit static 1 1 3 1 exit dynamic fact 1 1 6 1 call static _195168 is 2 1 6 1 exit static 2 is 2 1 0 O exit dynamic fact 2 2 X 2 yes 14 2 3 Debugging Commands The following commands can be given by the user when the debugger stops at a either a spypoint or a leashed event a Abort The predicate abort 0 is called This sets the flags debug and trace to off and the debugger is exited 14 2 THE DEBUGGER 345 Creep The debugger continues execution until the next trace event At each event a trace message is written and if the
229. tream S permission_error input binary_stream S The argument S refers to a binary stream representation_error character_code C The argument C was instan tiated but not a character code 4 1 PREDICATES 207 type_error integer C The argument C was instantiated but not an in teger See also character_code 1 4 1 227 2 Synopsis T1 X T2 Description Succeeds if the term T1 cannot be unified with the term T2 Behaves as if defined as follows T1 T2 T1 T2 fail NAS hase Ss Examples 7 9 19 yes X x no Errors None See also gt 2 4 1 228 gt 2 Synopsis T1 T2 Description Succeeds if the term T1 can be unified with the term T2 This predicate does not perform the occurs check i e X f X succeeds Behaves as if defined as follows T T 208 CHAPTER 4 BUILT IN PREDICATES Examples X x X x yes 9 19 no Errors None See also 2 unify_with_occurs_check 2 4 1 229 unify_with_occurs_check 2 Synopsis unify_with_occurs_check T1 T2 Description Succeeds if the term T1 can be unified with the term T2 This predicate performs the occurs check i e X X fails Examples unify_with_occurs_check x X X x yes unify_with_occurs_check X f X no Errors None See also gt 2 4 1 PREDICATES 209 4 1 230 2 Synopsis T1 T2
230. tream_alias user_input S findall P stream_property S P Ps S stream 0 P _532144 Ps mode read input alias user_input eof_action reset reposition false type text character_encoding utf_8 file_name user_input position stream_position 0 7 219 0 end_of_stream not yes Errors domain_error stream S The argument S was not a valid stream term domain_error stream_property T The argument T was not a valid stream property term See also open 4 stream_property 1 4 1 213 sub_atom 5 Synopsis sub_atom Atom Before Length After SubAtom Description Succeeds if the name of the atom Atom contains the name of the atom SubAtom of length Length characters which starts at index Before and ends at index After Examples sub_atom ab Before Length After SubAtom Before 0 Length 0 After 2 SubAtom Before 0 4 1 PREDICATES 197 Length 1 After 1 SubAtom a Before 0 Length 2 After 0 SubAtom ab Before Length After 1 SubAtom I or Before 1 Length 1 After 0 SubAtom b Il N Before Length After 0 SubAtom oS ll o ll y no Errors instantiation_error The argument Atom was not instantiated domain_error not_less_than_zero After The argument After was an integer less than zero domain_error not_less_than_zero Before The argument Before was an integer less than zero
231. ue false Possible Values This is a constant flag and cannot be changed from the default 4 3 FLAGS 231 4 3 13 number_output_base Description This flag determines the base which numbers are to be written with write_term 3 Default Value 10 Possible Values Any integer greater than or equal to 2 and less than or equal to 36 4 3 14 singleton_var_warnings Description A switch which controls the behaviour of consult 1 reconsult 1 and compile_file 2 when it encounters any singleton variables found in a term read as input Default Value on Possible Values on Print a warning message with a list of singleton variables for each term read off No warnings are printed 4 3 15 unknown Description The value of this flag determines the action taken when an unknown proce dure is called Default Value error 232 CHAPTER 4 BUILT IN PREDICATES Possible Values error The exception existence_error predicate F N is thrown where F N is the predicate indicator of the unknown procedure warning A warning is printed on the stream user_error the call then fails fail The call silently fails Chapter 5 The assoc library The predicates in this library implement an association list data type using binary trees Each element of an association list is a pair a key and a value The key is used to search for the associated value To use the predicates in this library you will need to load the assoc fas1 f
232. uery input methods An example of query input hook could be hook InputMethod Prompt RawInput InputMethod This is the term used to identify this input hook A query class would use this term to select this query input hook Prompt This is the term that should shown to the user as an indication that input is being requested RawInput The input which this hook has read Examples In this example we define three different query hooks class map and input Together they allow us to prompt the user for a single character code which is then mapped to a predetermined set of answer terms assert code_input_hook code Prompt RawInput prompt OldPrompt prompt Prompt catch get_code RawInput E prompt 01dPrompt throw E prompt OldPrompt Prompt _527312 RawInput _529296 OldPrompt _534016 34 CHAPTER 4 BUILT IN PREDICATES E _546736 yes add_query_input_hook code_input_hook yes assert code_map code Pairs RawInput Result Answer member Name Abbreviation Pairs member RawInput Abbreviation 1 Answer Name Result success Pairs _525536 RawInput _527488 Result _529888 Answer _531872 Name _536176 Abbreviation _537616 yes add_query_map_hook code_map yes assert ynm_class_hook yes_no_maybe gt y n or m code code yes 89 121 no 78 110 maybe 77 109 help_query yes add_query_c
233. ues with the original message argument The registration of term expansion hooks which are already registered has no effect The message that is generated by A should be either an empty list or a list where the last element must be the atom n1 and all of the other elements are of one of three forms see generate_message_lines 3 Format Args These are written as if there was a call to format Stream Format Args write_term Term Options These are written as if there was a call to write_term Stream Term Options nl This generates a newline as in a call to n1 0 When displayed all list elements between the nl elements are written on a separate line with the appropriate message severity prefix See print_message 2 Examples Here we add a generate message hook to customise the message displayed when we catch an existence error in the top level loop expand_term gm error existence_error predicate F N existence_error Goal not_applicable predicate F N gt 000PS tt gt O nl Existence error nl Goal in error q Goal nl 28 CHAPTER 4 BUILT IN PREDICATES The predicate q does not exist F N n1 Expansion assert Expansion add_generate_message gm E 531728 N _532496 Goal _537184 Expansion long line deleted yes foo a b c d OOOPS Existence error Goal in error foo a b c d The predicate foo 4 does not exist Errors
234. ument as a character code and print it lt N gt c Interpret the argument as a character code and print it N times d Interpret the argument as a number and print it in decimal 106 CHAPTER 4 BUILT IN PREDICATES f Interpret the argument as a floating point number and print it lt N gt f Interpret the argument as a floating point number and print it with a precision of N digits after the radix point i Ignore the argument k Pass the argument to write_canonical 2 n Print a newline lt N gt n Print a newline N times N Print a newline only if the output stream is not at column position zero p Pass the argument to print 2 q Pass the argument to writeq 2 r Interpret the argument as an integer and print it in radix 8 lt N gt r Interpret the argument as an integer and print it radix N The radix must be between 2 and 36 inclusive s Interpret the argument as a string and print it without quoting lt N gt s Interpret the argument as a string and print its first N characters t Reserved Do not use w Pass the argument to write 2 Print the character e Pass the argument to cal1 1 Examples format a 2a n foo foo foofo yes format a n 3 three thr yes format c 2c n 64 65 AA yes format d n 123 123 yes 4 1 PREDICATES 107 X is 1 3 format f 10f n X X 0 333333 0 3333333333 X 0 33
235. up_wf_goal 4 Unsuccessful goals are cached in the clause store using the predicate bup_fail_goal 2 The default option in the case Options is cache_goals off In the event that Options contains conflicting options the last such option in the list takes precedence Examples bup_compile grammar bup grammar pl dictionary_lookup vocabulary on BUP compilation input file grammar bup output file grammar pl Finished yes Errors bup_error could_not_open Filename 0 The file identified by Filename could not be opened bup_error could_not_read Filename Position Input could not be read from the grammar in file Filename at stream position Position bup_error empty_production Filename Position There is an empty production in the grammar in file Filename at stream position Position bup_error grammar_cycle NonTerminal The input grammar contains at least one cycle The atoms in the list NonTerminal are part of a cycle domain_error bup_compile_option Option The argument Option was not a valid BUP compiler option instantiation_error One of the arguments was not fully instantiated See also stream_position_byte_count 2 stream_position_character_count 2 stream_position_line_count 2 stream_position_line_position 2 6 1 3 bup_fail_goal 2 Synopsis bup_fail_goal NonTerminal Input 6 1 PREDICATES 243 Description This dynamic predicate is asserted by the parser when the compil
236. urrent_input Stream read_in Stream Words Examples See read_in 2 Errors See read_in 2 See also read_in 2 289 290 CHAPTER 11 THE READIN LIBRARY 11 1 2 read_in 2 Synopsis read_in Stream Words Description Reads input from Stream until a line is input which terminates with either an end of file or one of the characters or The argument Words is a list of atoms or numbers which are constructed from the characters given as input as follows e A whitespace character code which satisfies prolog_lexical_ws 1 is ignored A character code that either satisfies prolog_lexical_symbol 1 or is one of or is turned into a one character atom e A sequence of character codes all of which satisfy prolog_lexical_digit 1 is turned into a number e A sequence of character codes all of which satisfy prolog_lexical_letter 1 is turned into an atom Any of the character codes in the sequence that satisfy prolog_lexical_upper_case_letter 1 are converted into the equivalent lower case letter code before the atom is built Examples current_input Stream read_in Stream Words This is a line of input This is another line of input Stream stream 0 Words this is a line of input this is another line of input yes current_input Stream read_in Stream Words 2468 10 Stream stream 0 Words 2 4 6 8 10 yes Errors See get_code 2 11
237. we are prepared to sacrifice some space we could use a further option which caches terminals recognised by our dictionary look up predicate in the clause store to avoid recomputation meaning that the next time the terminal is processed our predicate isn t called as the terminal is found in the cache Since caching results makes no sense if there is no dictionary look up predicate we are left with the following options which can be passed to bup_compile 3 should no such option be given there is no dictionary look up and no caching of results lookup_dictionary Functor off Call the predicate Functor 4 when a terminal is not found in the grammar Do not cache successes lookup_dictionary Functor on Call the predicate Functor 4 when a terminal is not found in the grammar Cache successes to avoid recomputation The following is an example of using a predicate function for dictionary look up We first compile the grammar given earlier to use dictionary look up and we tell the compiler that we will define a predicate vocabulary 4 that the parser should call We then load the compiled grammar bup_compile grammar bup grammar pl dictionary_lookup vocabulary on BUP compilation input file grammar bup output file grammar pl Finished yes grammar Singletons File home bwat BarrysProlog bin linux_x86_64 grammar pl Position start of term line number 8 column number 0
238. where Y is a random variable distributed according to the x distribution with N degrees of freedom Examples chi_squared_cdf 3 3 Answer Answer 0 608375 yes Errors domain_error not_less_than_one N The argument N was less than 1 domain_error not_less_than_zero X The argument X was less than 0 instantiation_error Either the argument X or the argument N was an uninstantiated variable 311 312 CHAPTER 13 THE STATISTICS LIBRARY type_error integer N The argument N did not evaluate to an integer Also as the arguments X and N are evaluated errors may be thrown by eval 2 See also None 13 1 2 chi_squared_pdf 3 Synopsis chi_squared_pdf X N Answer Description Answer is the probability density at Y X where Y is a random variable distributed according to the x distribution with N degrees of freedom Examples chi_squared_pdf 0 2 Answer Answer 0 5 yes Errors domain_error not_less_than_one N The argument N was less than 1 domain_error not_less_than_zero X The argument X was less than 0 instantiation_error Either the argument X or the argument N was an uninstantiated variable type_error integer N The argument N did not evaluate to an integer Also as the arguments X and N are evaluated errors may be thrown by eval 2 See also None 13 1 PREDICATES 313 13 1 3 chi_squared_quantile 3 Synopsis chi_squared_quantile X N Answer Descr
239. wline code but not an end of file code Examples query_read_line user_input Line This is a line Line 84 104 105 115 32 105 115 32 97 32 108 105 110 101 46 10 yes Errors See get_code 2 See also get_code 2 query_input 3 4 1 187 read 1 Synopsis read T 4 1 PREDICATES Description Behaves as if it were defined as follows read Term current_input S read S Term Examples See read 2 Errors See read 2 See also current_input 1 read 2 4 1 188 read 2 Synopsis read S T Description Behaves as if it were defined as follows read S Term read_term S Term Examples See read_term 3 Errors See read_term 3 See also read_term 3 4 1 189 read_term 2 Synopsis read_term T 0 173 174 CHAPTER 4 BUILT IN PREDICATES Description Behaves as if it were defined as follows read_term Term Options current_input S read_term S Term Options Examples See read_term 3 Errors See read_term 3 See also current_input 1 read_term 3 4 1 190 read_term 3 Synopsis read_term S T 0 Description A term T is read from the the stream S with auxiliary information determined by the list of options O The valid options are position P P is unified with the position of the stream S corresponding to the start of the term that was read singletons V Vis unified with a list of A B pairs such th
240. writeq 1 Synopsis writeq T 4 1 PREDICATES Description Behaves as if it were defined as follows writeq Term current_output S writeq S Term Examples See writeq 2 Errors See writeq 2 See also current_output 1 writeq 2 4 1 236 writeq 2 Synopsis writeq S T Description Behaves as if it were defined as follows writeq S Term 213 write_term S Term quoted true numbervars true Examples See write_term 2 Errors See write_term 2 See also write_term 2 4 1 237 write_canonical 1 Synopsis write_canonical T 214 CHAPTER 4 BUILT IN PREDICATES Description Behaves as if it were defined as follows write_canonical Term current_output S write_canonical S Term Examples See write_canonical 2 Errors See write_canonical 2 See also current_output 1 write_canonical 2 4 1 238 write_canonical 2 Synopsis write_canonical S T Description Behaves as if it were defined as follows write_canonical S Term write_term S Term quoted true ignore_ops true Examples See write_term 2 Errors See write_term 2 See also write_term 2 4 1 239 write_term 2 Synopsis write_term T 0 4 1 PREDICATES 215 Description Behaves as if it were defined as follows write_term T 0 current_output S write_term S T 0 Examples See write_term 3 Errors See write_term 3 See also current_ou
241. y text shown in a mono width typeface The following is an example of an interaction where the user instructs the system to print the string Hello World followed by a newline print Hello World nl Hello World yes Every now and then a line of text representing an interaction with the system is too long to be shown as one line in the manual In this case the line is broken up to make it look better on the page 1 2 2 Predicate reference Whenever a predicate needs to be referenced in the text the predicate in dicator is given A predicate indicator is the name of the predicate and the arity of the predicate separated by a slash operator For instance n1 0 2 CHAPTER 1 INTRODUCTION print 1 Several predicates may share the same name but the name and arity combination is unique 1 2 3 Mode declaration For each predicate described in this manual a mode declaration is given A mode declaration prefixes each predicate argument with one of the following operators or As an example here is the mode declaration for atom_index 3 atom_index A I C The following table shows the meaning of these operators This argument is an input argument It must not be an uninstantiated variable This argument is an output argument It must be an uninstantiated vari able which will be instantiated by the predicate This argument is either an input or an output argument The may be an uninstantiated vari
242. y you will need to load the file debug fasl One way of doing this is with the call ensure_loaded runtime debug Once loaded the debugger s behaviour is configured with the Prolog flags debug and trace debug When set to off then the debugger is disengaged and apart from the debugger taking up space in the clause store and the code store the the operation of the system is no different from the case where the debugger has not been loaded When the flag is set to on then the debugger is engaged and all necessary debug information is recorded during execution which leads to an increase in resource usage It is possible to set the value of debug to on when the debugger is not loaded This should be avoided as it offers no functional gain and Prolog code is executed more slowly trace The value of this flag only has an effect when the debugger is engaged When the debugger is engaged and the flag trace is set to off then no trace output is generated until a spypoint is reached When the debugger is engaged and the flag trace is set to on then all events are traced and should the traced event be leashed then the execution is stopped until a debug command is given 14 2 THE DEBUGGER 343 14 2 2 Trace output Each trace output has six fields A typical example is the following 0 O call dynamic fact 3 _195168 The six fields are to be interpreted as follows This trace relates to a spypoint Another possibility is two sp
243. ynamic ensure_loaded include initialization multifile gt gt div rem mod lt lt gt gt kk a Table 3 1 The Prolog operator table 3 2 EXCEPTIONS 19 error existence_error A B existence_error G N A B Argument number N of the goal G was the object B of type A which does not exist error instantiation_error instantiation_error G N Argument num ber N of the goal G was uninstantiated error lexical_error M lexical_error G A B M The goalG caused a lexical error in the file named A at position B The term M is a de scriptive message error permission_error A B C permission_error G A B C The action A on the object C of type B in goal G could not be performed due to lack of permission error representation_error A representation_error G N A Argument number N of the goal G could not be represented as a value of the type A error resource_error code _ There was no room left in the code sec tion The second argument is a dummy variable error resource_error clause_store _ There was no room left in the clause store The second argument is a dummy variable error resource_error constants _ There was no room left in the con stants table The second argument is a dummy variable error resource_error functors _ There was no room left in the func tors table The second argument is a dummy variable error resource_error heap _ There was no room left on

Barry's Prolog Reference Manual & User Guide

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Barry's Prolog Reference Manual &amp; User Guide

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Barry's Prolog Reference Manual & User Guide