# Properties of modules and predicates **URL:** \ **Category:** Wiki\ **Tags:** how-to\ **Created:** [July 4, 2020, 1:53pm UTC](https://swi-prolog.discourse.group/t/properties-of-modules-and-predicates/2597 "2020-07-04T13:53:52Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Wiki](https://avatars.discourse-cdn.com/v4/letter/w/e8c25b/32.png) [@Wiki](https://swi-prolog.discourse.group/u/Wiki)\ **Post date:** [July 4, 2020, 1:53pm UTC](https://swi-prolog.discourse.group/t/properties-of-modules-and-predicates/2597/1 "2020-07-04T13:53:52Z")
> Note: If you have [Trust level](https://blog.discourse.org/2018/06/understanding-discourse-trust-levels/): [Basic](https://swi-prolog.discourse.group/badges/1/basic) you can edit this by clicking on the edit icon in the lower right. ![Capture](https://global.discourse-cdn.com/free1/uploads/swiprolog/original/1X/bfd4c3b77dc7f3f98ece3d5ae3202fcccb0fb8b3.png) > Note: Do not reply to this topic; questions, concerns, comments, etc. are to be handled in > [Wiki Discussion: Properties of modules and predicates](https://swi-prolog.discourse.group/t/wiki-discussion-using-listing-n/2598) * * * The built-in predicate listing/0,1,2 from [library(listing)](https://www.swi-prolog.org/pldoc/man?section=listing) is used to list the contents of the database. It is more commonly thought of as listing facts, predicates, clauses and filtering based on module or predicate/fact name. Using listing/0 will list the contents of the global `user` module. ([ref](https://stackoverflow.com/a/46798586/1243762)) * * * listing/0 is the same as ```prolog user:listing. ``` or ```prolog listing(user:_). ``` * * * listing/1 can be used to show the same predicate in different modules. Note: The predicate `group` is from my own code, so this is exact predicate will not work for you. ```prolog ?- listing(group). ``` > **Example** > > ```prolog > ?- listing(group). > rfc5234:group([40|T0], T, [40|A], B) :- > 'cwsp*'(T0, T1, A, C), > alternation(T1, T2, C, D), > 'cwsp*'(T2, [41|T], D, E), > E=[41|B]. > > rfc5234_format_preserving:group(Structure, [40|A], B) :- > 'cwsp*'(Before, A, C), > alternation(Alternation, C, D), > 'cwsp*'(After, D, E), > E=[41|F], > group_structure(Before, > After, > Alternation, > Structure), > B=F. > > rfc5234_structure_preserving:group(Structure, [40|A], B) :- > 'cwsp*'(_, A, C), > alternation(Alternation, C, D), > 'cwsp*'(_, D, E), > E=[41|F], > group_structure(Alternation, Structure), > B=F. > > true. > > ``` * * * To see the list of current modules loaded use current\_module/1. ```prolog ?- current_module(M). ``` > **Example** > > ```prolog > ?- current_module(M). > M = sandbox ; > M = read_util ; > M = error ; > M = qsave ; > M = swi_option ; > M = prolog_listing ; > M = predopts_analysis ; > M = prolog_history ; > M = prolog_stack ; > M = predicate_options ; > M = prolog ; > M = shlib ; > M = pce_swi_hooks ; > M = prolog_clause ; > M = lists ; > M = arithmetic ; > M = prolog_debug ; > M = settings ; > M = prolog_system_predicate_options ; > M = ansi_term ; > M = prolog_operator ; > M = pce_expansion ; > M = listing ; > M = win_menu ; > M = link_xpce ; > M = base32 ; > M = system ; > M = prolog_source ; > M = user ; > false. > > ``` * * * Different modules can be selected for use with listing/0,1,2 using either ```prolog :listing. ``` or ```prolog listing(:_). ``` * * * To see the list of current predicates loaded use current\_predicate/1. > **Examples** > > ```prolog > ?- aggregate_all(count,current_predicate(_),Count). > Count = 1330. > > ?- current_predicate(append/2). > true. > > ?- current_predicate(append/N). > N = 1 ; > N = 2 ; > false. > > ?- current_predicate(lists:Name). > Name = prefix/2 ; > Name = must_be/2 ; > Name = remove_dup_keys/2 ; > Name = numlist_/3 ; > Name = remove_same_key/3 ; > Name = max_list/3 ; > Name = select/3 ; > Name = subset/2 ; > Name = is_set/1 ; > Name = intersection/3 ; > Name = nth_gen/5 ; > Name = '$autoload'/3 ; > Name = find_nth0/4 ; > Name = append/2 ; > Name = min_list/2 ; > Name = sum_list/2 ; > Name = min_member/2 ; > Name = reverse/4 ; > Name = flatten/2 ; > Name = member_/3 ; > Name = reverse/2 ; > Name = proper_length/2 ; > Name = select3_/4 ; > Name = select/4 ; > Name = flatten/3 ; > Name = min_member_/3 ; > Name = nth0/3 ; > Name = sort/4 ; > Name = nextto/3 ; > Name = nth1/4 ; > Name = number_list/3 ; > Name = member/2 ; > Name = min_list/3 ; > Name = sum_list/3 ; > Name = max_member_/3 ; > Name = append/3 ; > Name = subtract/3 ; > Name = union/3 ; > Name = list_to_set/2 ; > Name = generate_nth/5 ; > Name = last_/3 ; > Name = numlist/3 ; > Name = max_list/2 ; > Name = nth0_det/3 ; > Name = perm/2 ; > Name = max_member/2 ; > Name = nth1/3 ; > Name = permutation/2 ; > Name = append_/2 ; > Name = same_length/2 ; > Name = select4_/4 ; > Name = last/2 ; > Name = pairs_keys/2 ; > Name = delete/3 ; > Name = selectchk/4 ; > Name = succ/2 ; > Name = selectchk/3 ; > Name = nth0/4 ; > false. > > ``` * * * Different predicate/fact names can be selected using either ```prolog :listing(). ``` or ```prolog listing(:). ``` > **Examples** > > ```prolog > ?- listing(lists:append/2). > append(ListOfLists, List) :- > must_be(list, ListOfLists), > append_(ListOfLists, List). > > true. > > ?- lists:listing(append/2). > append(ListOfLists, List) :- > must_be(list, ListOfLists), > append_(ListOfLists, List). > > true. > > ?- lists:listing(append/N). > append(ListOfLists, List) :- > must_be(list, ListOfLists), > append_(ListOfLists, List). > > append([], L, L). > append([H|T], L, [H|R]) :- > append(T, L, R). > > true. > > ``` * * * Predicates have properties which can be accessed with predicate\_property/2. > **Examples** > > ```prolog > ?- aggregate_all(count,predicate_property(H,multifile),Count). > Count = 23. > > ?- aggregate_all(count,predicate_property(H,imported_from(F)),Count). > Count = 117. > > ?- predicate_property(H,multifile). > H = expand_query(_9774, _9776, _9778, _9780) ; > H = prolog_load_file(_10446, _10448) ; > H = portray(_11114) ; > H = pce_pre_expansion_hook(_11780, _11782) ; > H = prolog_file_type(_12448, _12450) ; > H = prolog_exception_hook(_13116, _13118, _13120, _13122) ; > H = expand_answer(_13788, _13790) ; > H = resource(_14456, _14458, _14460) ; > H = message_property(_15126, _15128) ; > H = url_path(_15794, _15796) ; > H = term_expansion(_16462, _16464, _16466, _16468) ; > H = message_hook(_17134, _17136, _17138) ; > H = prolog_clause_name(_17804, _17806) ; > H = exception(_18472, _18474, _18476) ; > H = library_directory(_19142) ; > H = prolog_list_goal(_19808) ; > H = goal_expansion(_20474, _20476, _20478, _20480) ; > H = prolog_predicate_name(_21146, _21148) ; > H = term_expansion(_21814, _21816) ; > H = pce_post_expansion_hook(_22482, _22484) ; > H = file_search_path(_23150, _23152) ; > H = goal_expansion(_23818, _23820) ; > H = resource(_24486, _24488) ; > false. > > ?- predicate_property(PI,number_of_rules(C)),C > 1. > PI = subset(_646, _648), > C = 2 ; > PI = absolute_file_name(_1694, _1696, _1698), > C = 2 ; > PI = print_message(_2744, _2746), > C = 2 ; > PI = portray(_3792), > C = 4 ; > PI = spy(_4838), > C = 5 ; > PI = prolog_file_type(_5884, _5886), > C = 2 ; > PI = stream_position_data(_6932, _6934, _6936), > C = 2 ; > PI = absolute_file_name(_7982, _7984), > C = 3 ; > PI = intersection(_9030, _9032, _9034), > C = 3 ; > PI = union(_10080, _10082, _10084), > C = 3 ; > PI = module_property(_11130, _11132), > C = 3 ; > PI = current_predicate(_12178, _12180), > C = 4 ; > PI = message_hook(_13226, _13228, _13230), > C = 10 ; > PI = source_file_property(_14276, _14278), > C = 2 ; > PI = prolog_list_goal(_15324), > C = 2 ; > PI = subtract(_16370, _16372, _16374), > C = 3 ; > PI = prolog_predicate_name(_17420, _17422), > C = 2 ; > PI = file_search_path(_18468, _18470), > C = 15 ; > PI = prolog_load_context(_19516, _19518), > C = 11 ; > PI = aggregate_all(_20564, _20566, _20568), > C = 8 ; > PI = flag(_21614, _21616, _21618), > C = 2 ; > PI = list_predicates(_22664), > C = 2 ; > false. > > ?- predicate_property(append(A,B,C),P). > P = interpreted ; > P = visible ; > P = static ; > P = imported_from(lists) ; > P = file('c:/program files/swipl/library/lists.pl') ; > P = line_count(123) ; > P = nodebug ; > P = number_of_clauses(2) ; > P = number_of_rules(1) ; > P = last_modified_generation(5699) ; > P = defined ; > P = size(480). > > ``` NB append/3 will return a result but most likely not the one you expect. If you see `imported_from(yall)` then this is probably not what you want. In other words don’t use the predicate indicator notation of `/`, use a template form `()` > **Example** > > ```prolog > ?- predicate_property(append/3,P). > P = interpreted ; > P = visible ; > P = static ; > P = imported_from(yall) ; > P = transparent ; > P = (meta_predicate? / 0) ; > P = file('c:/program files/swipl/library/yall.pl') ; > P = line_count(275) ; > P = number_of_clauses(1) ; > P = number_of_rules(1) ; > P = last_modified_generation(5613) ; > P = defined ; > P = size(384). > > ``` TODO: Create example with property `wrapped`. See: [prolog\_wrap.pl – Wrapping predicates](https://www.swi-prolog.org/pldoc/doc/_SWI_/library/prolog_wrap.pl) TODO: Create example with [quasiquoation](https://www.swi-prolog.org/pldoc/man?section=quasiquotations). TODO: Create example using jiti\_list/1 TODO: Add [predicate\_options](https://www.swi-prolog.org/pldoc/man?section=predicate_options) examples. * * * Modules have properties which can be accessed with module\_property/2. > **Examples** > > ```prolog > ?- module_property(user,Property). > Property = class(user) ; > Property = exports([]) ; > Property = exported_operators([]) ; > Property = size(17296) ; > Property = program_size(5184) ; > Property = last_modified_generation(7106). > > ?- module_property(Module,file(F)). > Module = pce_swi_hooks, > F = 'c:/program files/swipl/xpce/prolog/lib/swi_hooks.pl' ; > Module = prolog_stack, > F = 'c:/program files/swipl/library/prolog_stack.pl' ; > Module = prolog_clause, > F = 'c:/program files/swipl/library/prolog_clause.pl' ; > Module = predicate_options, > F = 'c:/program files/swipl/library/predicate_options.pl' ; > Module = read_util, > F = 'c:/program files/swipl/library/readutil.pl' ; > Module = win_menu, > F = 'c:/program files/swipl/library/win_menu.pl' ; > Module = swi_option, > F = 'c:/program files/swipl/library/option.pl' ; > Module = prolog_listing, > F = 'c:/program files/swipl/library/listing.pl' ; > Module = prolog_operator, > F = 'c:/program files/swipl/library/operators.pl' ; > Module = link_xpce, > F = 'c:/program files/swipl/swipl-win.rc' ; > Module = prolog_system_predicate_options, > F = 'c:/program files/swipl/library/dialect/swi/syspred_options.pl' ; > Module = aggregate, > F = 'c:/program files/swipl/library/aggregate.pl' ; > Module = lists, > F = 'c:/program files/swipl/library/lists.pl' ; > Module = prolog_source, > F = 'c:/program files/swipl/library/prolog_source.pl' ; > Module = shlib, > F = 'c:/program files/swipl/library/shlib.pl' ; > Module = error, > F = 'c:/program files/swipl/library/error.pl' ; > Module = base32, > F = 'c:/program files/swipl/library/base32.pl' ; > Module = settings, > F = 'c:/program files/swipl/library/settings.pl' ; > Module = arithmetic, > F = 'c:/program files/swipl/library/arithmetic.pl' ; > Module = prolog_debug, > F = 'c:/program files/swipl/library/debug.pl' ; > Module = ansi_term, > F = 'c:/program files/swipl/library/ansi_term.pl' ; > Module = prolog_history, > F = 'c:/program files/swipl/library/prolog_history.pl' ; > false. > > ?- module_property(Module,class(Class)). > Module = pce_swi_hooks, > Class = development ; > Module = prolog_stack, > Class = library ; > Module = prolog_clause, > Class = library ; > Module = predicate_options, > Class = library ; > Module = sandbox, > Class = user ; > Module = read_util, > Class = library ; > Module = listing, > Class = user ; > Module = prolog, > Class = user ; > Module = win_menu, > Class = library ; > Module = swi_option, > Class = library ; > Module = prolog_listing, > Class = library ; > Module = pce_expansion, > Class = user ; > Module = prolog_operator, > Class = library ; > Module = link_xpce, > Class = library ; > Module = prolog_system_predicate_options, > Class = library ; > Module = aggregate, > Class = library ; > Module = lists, > Class = library ; > Module = prolog_source, > Class = library ; > Module = shlib, > Class = library ; > Module = error, > Class = library ; > Module = qsave, > Class = user ; > Module = Class, > Class = system ; > Module = base32, > Class = library ; > Module = settings, > Class = library ; > Module = arithmetic, > Class = library ; > Module = prolog_debug, > Class = library ; > Module = ansi_term, > Class = library ; > Module = predopts_analysis, > Class = user ; > Module = prolog_history, > Class = library ; > Module = Class, Class = user ; > false. > > ``` * * * Some of the [Prolog flags](https://www.swi-prolog.org/pldoc/man?section=flags) can be set per module. > **Example** > > ```prolog > ?- user:current_prolog_flag(double_quotes,Value). > Value = string. > > ?- user:set_prolog_flag(double_quotes,codes). > true. > > ?- user:current_prolog_flag(double_quotes,Value). > Value = codes. > > ?- current_module(M),current_prolog_flag(M:double_quotes,Value). > M = pce_swi_hooks, > Value = string ; > M = prolog_stack, > Value = string ; > M = prolog_clause, > Value = string ; > M = predicate_options, > Value = string ; > M = read_util, > Value = string ; > M = prolog, > Value = string ; > M = win_menu, > Value = string ; > M = link_xpce, > Value = string ; > M = prolog_system_predicate_options, > Value = string ; > M = shlib, > Value = string ; > M = qsave, > Value = string ; > M = system, > Value = string ; > M = base32, > Value = string ; > M = ansi_term, > Value = string ; > M = predopts_analysis, > Value = string ; > M = prolog_history, > Value = string ; > M = user, > Value = codes ; > false. > > ``` * * * Sometimes the output is very long and scrolls off the screen. To save the output to a file use [with\_output\_to\_file/2](https://www.swi-prolog.org/pack/file_details/fileutils/prolog/fileutils.pl). > **Example** > > ```prolog > ?- use_module(library(fileutils)). > true. > > % Yes you can load a module from top. > > ?- with_output_to_file('C:/Users/Eric/Documents/append.listing.pl',listing(append)). > true. > > ``` > > append.listing.pl > > ```prolog > lists:append(ListOfLists, List) :- > must_be(list, ListOfLists), > append_(ListOfLists, List). > > lists:append([], L, L). > lists:append([H|T], L, [H|R]) :- > append(T, L, R). > > % Foreign: system:append/1 > > ``` Note: This uses package [fileutils](https://www.swi-prolog.org/pack/file_details/fileutils/prolog/fileutils.pl) which must be installed. > **How to install package fileutils** > > ```prolog > % Check to make sure it is not already installed. > > ?- pack_list_installed. > Installed packages (6): > > i edcg@0.9.1.2 - Extended DCG > i func@0.4.2 - Function application and composition > i function_expansion@0.1.2 - Help for writing function-like macros > i list_util@0.13.0 - Predicates for working with lists > i quickcheck@0.3.0 - QuickCheck randomized testing > i sldnfdraw@1.61 - SLDNF Draw is a Prolog program that draws SLDNF Trees in LaTeX > true. > > % Check to make sure it is available. > > ?- pack_search(fileutils). > % Contacting server at https://www.swi-prolog.org/pack/query ... ok > p fileutils@0.3.5 - Utilities for reading, writing and finding files > true. > > % Install package fileutils > > ?- pack_install(fileutils). > % Contacting server at https://www.swi-prolog.org/pack/query ... ok > Install fileutils@0.3.5 from https://raw.githubusercontent.com/samer--/prolog/master/fileutils/release/fileutils-0.3.5.tgz Y/n? > % Contacting server at https://www.swi-prolog.org/pack/query ... > ok > % "fileutils-0.3.5.tgz" was downloaded 10 times > Package: fileutils > Title: Utilities for reading, writing and finding files > Installed version: 0.3.5 > Author: Samer Abdallah > Download URL: https://raw.githubusercontent.com/samer--/prolog/master/fileutils/release/fileutils-0.3.5.tgz > Install "fileutils-0.3.5.tgz" (20,606 bytes) Y/n? > true. > > % Check to see it was installed > > ?- pack_list_installed. > Installed packages (7): > > i edcg@0.9.1.2 - Extended DCG > i fileutils@0.3.5 - Utilities for reading, writing and finding files > i func@0.4.2 - Function application and composition > i function_expansion@0.1.2 - Help for writing function-like macros > i list_util@0.13.0 - Predicates for working with lists > i quickcheck@0.3.0 - QuickCheck randomized testing > i sldnfdraw@1.61 - SLDNF Draw is a Prolog program that draws SLDNF Trees in LaTeX > true. > > ``` * * * Most libraries are located in the `library` directory under `current_prolog_flag(home,Value).`, e.g. ```prolog ?- current_prolog_flag(home,Value). Value = 'c:/program files/swipl'. C:/program files/swipl/library ``` however some libraries are not at the root level of the `library` directory but in a subdirectory. One popular library as such is `library\dcg\basics.pl`. dcg\basics can be loaded with ```prolog use_module(library(dcg/basics)). ``` then the module name can be found using current\_module/1, e.g. `current_module(M).` which shows that the module name for dcg/basics is `dcg_basics`. * * * With SWI-Prolog - [unit test](https://www.swi-prolog.org/pldoc/man?section=unitbox) using ```prolog :- begin_tests(). ... :- end_tests(). ``` the section (test box) is converted into a module with the name `plunit_`. The test in the section are proper predicates that can be listed using the constructed module name. * * * TODO: Add example based on [SO Q&A](https://stackoverflow.com/q/54239968/1243762) * * * Note: Some editors have these types of queries built-in. As I use [VSC](https://code.visualstudio.com/) (Visual Studio Code) I have to rely on using these instead. * * * External pages: [Using SWI-Prolog’s modules](https://chiselapp.com/user/ttmrichter/repository/gng/doc/trunk/output/tutorials/swiplmodtut.html)