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    1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  1985-2025, University of Amsterdam
    7                              VU University Amsterdam
    8                              CWI, Amsterdam
    9                              SWI-Prolog Solutions b.v.
   10    All rights reserved.
   11
   12    Redistribution and use in source and binary forms, with or without
   13    modification, are permitted provided that the following conditions
   14    are met:
   15
   16    1. Redistributions of source code must retain the above copyright
   17       notice, this list of conditions and the following disclaimer.
   18
   19    2. Redistributions in binary form must reproduce the above copyright
   20       notice, this list of conditions and the following disclaimer in
   21       the documentation and/or other materials provided with the
   22       distribution.
   23
   24    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   25    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   26    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   27    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   28    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   29    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   30    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   31    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   32    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   33    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   34    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   35    POSSIBILITY OF SUCH DAMAGE.
   36*/
   37
   38:- module('$syspreds',
   39          [ leash/1,
   40            visible/1,
   41            style_check/1,
   42            flag/3,
   43            atom_prefix/2,
   44            dwim_match/2,
   45            source_file_property/2,
   46            source_file/1,
   47            source_file/2,
   48            unload_file/1,
   49            exists_source/1,                    % +Spec
   50            exists_source/2,                    % +Spec, -Path
   51            prolog_load_context/2,
   52            stream_position_data/3,
   53            current_predicate/2,
   54            '$defined_predicate'/1,
   55            predicate_property/2,
   56            '$predicate_property'/2,
   57            (dynamic)/2,                        % :Predicates, +Options
   58            clause_property/2,
   59            current_module/1,                   % ?Module
   60            module_property/2,                  % ?Module, ?Property
   61            module/1,                           % +Module
   62            current_trie/1,                     % ?Trie
   63            trie_property/2,                    % ?Trie, ?Property
   64            working_directory/2,                % -OldDir, +NewDir
   65            shell/1,                            % +Command
   66            on_signal/3,
   67            current_signal/3,
   68            format/1,
   69            garbage_collect/0,
   70            set_prolog_stack/2,
   71            prolog_stack_property/2,
   72            absolute_file_name/2,
   73            tmp_file_stream/3,                  % +Enc, -File, -Stream
   74            call_with_depth_limit/3,            % :Goal, +Limit, -Result
   75            call_with_inference_limit/3,        % :Goal, +Limit, -Result
   76            rule/2,                             % :Head, -Rule
   77            rule/3,                             % :Head, -Rule, ?Ref
   78            numbervars/3,                       % +Term, +Start, -End
   79            term_string/3,                      % ?Term, ?String, +Options
   80            thread_create/2,                    % :Goal, -Id
   81            thread_join/1,                      % +Id
   82            sig_block/1,                        % :Pattern
   83            sig_unblock/1,                      % :Pattern
   84            transaction/1,                      % :Goal
   85            transaction/2,                      % :Goal, +Options
   86            transaction/3,                      % :Goal, :Constraint, +Mutex
   87            snapshot/1,                         % :Goal
   88            undo/1,                             % :Goal
   89            set_prolog_gc_thread/1,		% +Status
   90
   91            '$wrap_predicate'/5,                % :Head, +Name, -Closure, -Wrapped, +Body
   92            '$predicate_source_location'/2,     % :Head, -File:Line
   93            '$addr2line_location'/3             % +Description, -File, -Line
   94          ]).   95
   96:- meta_predicate
   97    dynamic(:, +),
   98    transaction(0),
   99    transaction(0,0,+),
  100    snapshot(0),
  101    rule(:, -),
  102    rule(:, -, ?),
  103    sig_block(:),
  104    sig_unblock(:).  105
  106
  107                /********************************
  108                *           DEBUGGER            *
  109                *********************************/
 map_bits(:Pred, +Modify, +OldBits, -NewBits)
  113:- meta_predicate
  114    map_bits(2, +, +, -).  115
  116map_bits(_, Var, _, _) :-
  117    var(Var),
  118    !,
  119    '$instantiation_error'(Var).
  120map_bits(_, [], Bits, Bits) :- !.
  121map_bits(Pred, [H|T], Old, New) :-
  122    map_bits(Pred, H, Old, New0),
  123    map_bits(Pred, T, New0, New).
  124map_bits(Pred, +Name, Old, New) :-     % set a bit
  125    !,
  126    bit(Pred, Name, Bits),
  127    !,
  128    New is Old \/ Bits.
  129map_bits(Pred, -Name, Old, New) :-     % clear a bit
  130    !,
  131    bit(Pred, Name, Bits),
  132    !,
  133    New is Old /\ (\Bits).
  134map_bits(Pred, ?(Name), Old, Old) :-   % ask a bit
  135    !,
  136    bit(Pred, Name, Bits),
  137    Old /\ Bits > 0.
  138map_bits(_, Term, _, _) :-
  139    '$type_error'('+|-|?(Flag)', Term).
  140
  141bit(Pred, Name, Bits) :-
  142    call(Pred, Name, Bits),
  143    !.
  144bit(_:Pred, Name, _) :-
  145    '$domain_error'(Pred, Name).
  146
  147:- public port_name/2.                  % used by library(test_cover)
  148
  149port_name(      call, 2'000000001).
  150port_name(      exit, 2'000000010).
  151port_name(      fail, 2'000000100).
  152port_name(      redo, 2'000001000).
  153port_name(     unify, 2'000010000).
  154port_name(     break, 2'000100000).
  155port_name(  cut_call, 2'001000000).
  156port_name(  cut_exit, 2'010000000).
  157port_name( exception, 2'100000000).
  158port_name(       cut, 2'011000000).
  159port_name(       all, 2'000111111).
  160port_name(      full, 2'000101111).
  161port_name(      half, 2'000101101).     % '
  162
  163leash(Ports) :-
  164    '$leash'(Old, Old),
  165    map_bits(port_name, Ports, Old, New),
  166    '$leash'(_, New).
  167
  168visible(Ports) :-
  169    '$visible'(Old, Old),
  170    map_bits(port_name, Ports, Old, New),
  171    '$visible'(_, New).
  172
  173style_name(atom,            0x0001) :-
  174    print_message(warning, decl_no_effect(style_check(atom))).
  175style_name(singleton,       0x0042).            % semantic and syntactic
  176style_name(discontiguous,   0x0008).
  177style_name(charset,         0x0020).
  178style_name(no_effect,       0x0080).
  179style_name(var_branches,    0x0100).
 style_check(+Spec) is nondet
  183style_check(Var) :-
  184    var(Var),
  185    !,
  186    '$instantiation_error'(Var).
  187style_check(?(Style)) :-
  188    !,
  189    (   var(Style)
  190    ->  enum_style_check(Style)
  191    ;   enum_style_check(Style)
  192    ->  true
  193    ).
  194style_check(Spec) :-
  195    '$style_check'(Old, Old),
  196    map_bits(style_name, Spec, Old, New),
  197    '$style_check'(_, New).
  198
  199enum_style_check(Style) :-
  200    '$style_check'(Bits, Bits),
  201    style_name(Style, Bit),
  202    Bit /\ Bits =\= 0.
 flag(+Name, -Old, +New) is det
True when Old is the current value associated with the flag Name and New has become the new value.
  210flag(Name, Old, New) :-
  211    Old == New,
  212    !,
  213    get_flag(Name, Old).
  214flag(Name, Old, New) :-
  215    with_mutex('$flag', update_flag(Name, Old, New)).
  216
  217update_flag(Name, Old, New) :-
  218    get_flag(Name, Old),
  219    (   atom(New)
  220    ->  set_flag(Name, New)
  221    ;   Value is New,
  222        set_flag(Name, Value)
  223    ).
  224
  225
  226                /********************************
  227                *             ATOMS             *
  228                *********************************/
  229
  230dwim_match(A1, A2) :-
  231    dwim_match(A1, A2, _).
  232
  233atom_prefix(Atom, Prefix) :-
  234    sub_atom(Atom, 0, _, _, Prefix).
  235
  236
  237                /********************************
  238                *             SOURCE            *
  239                *********************************/
 source_file(-File) is nondet
source_file(+File) is semidet
True if File is loaded into Prolog. If File is unbound it is bound to the canonical name for it. If File is bound it succeeds if the canonical name as defined by absolute_file_name/2 is known as a loaded filename.

Note that Time = 0 is used by PlDoc and other code that needs to create a file record without being interested in the time.

  252source_file(File) :-
  253    (   current_prolog_flag(access_level, user)
  254    ->  Level = user
  255    ;   true
  256    ),
  257    (   ground(File)
  258    ->  (   '$time_source_file'(File, Time, Level)
  259        ;   absolute_file_name(File, Abs),
  260            '$time_source_file'(Abs, Time, Level)
  261        ), !
  262    ;   '$time_source_file'(File, Time, Level)
  263    ),
  264    float(Time).
 source_file(+Head, -File) is semidet
source_file(?Head, ?File) is nondet
True when Head is a predicate owned by File.
  271:- meta_predicate source_file(:, ?).  272
  273source_file(M:Head, File) :-
  274    nonvar(M), nonvar(Head),
  275    !,
  276    (   '$c_current_predicate'(_, M:Head),
  277        predicate_property(M:Head, multifile)
  278    ->  multi_source_file(M:Head, File)
  279    ;   '$source_file'(M:Head, File)
  280    ).
  281source_file(M:Head, File) :-
  282    (   nonvar(File)
  283    ->  true
  284    ;   source_file(File)
  285    ),
  286    '$source_file_predicates'(File, Predicates),
  287    '$member'(M:Head, Predicates).
  288
  289multi_source_file(Head, File) :-
  290    State = state([]),
  291    nth_clause(Head, _, Clause),
  292    clause_property(Clause, source(File)),
  293    arg(1, State, Found),
  294    (   memberchk(File, Found)
  295    ->  fail
  296    ;   nb_linkarg(1, State, [File|Found])
  297    ).
 source_file_property(?File, ?Property) is nondet
True if Property is a property of the loaded source-file File.
  304source_file_property(File, P) :-
  305    nonvar(File),
  306    !,
  307    canonical_source_file(File, Path),
  308    property_source_file(P, Path).
  309source_file_property(File, P) :-
  310    property_source_file(P, File).
  311
  312property_source_file(modified(Time), File) :-
  313    '$time_source_file'(File, Time, user).
  314property_source_file(source(Source), File) :-
  315    (   '$source_file_property'(File, from_state, true)
  316    ->  Source = state
  317    ;   '$source_file_property'(File, resource, true)
  318    ->  Source = resource
  319    ;   Source = file
  320    ).
  321property_source_file(module(M), File) :-
  322    (   nonvar(M)
  323    ->  '$current_module'(M, File)
  324    ;   nonvar(File)
  325    ->  '$current_module'(ML, File),
  326        (   atom(ML)
  327        ->  M = ML
  328        ;   '$member'(M, ML)
  329        )
  330    ;   '$current_module'(M, File)
  331    ).
  332property_source_file(load_context(Module, Location, Options), File) :-
  333    clause(system:'$load_context_module'(File, Module, Options), true, Ref),
  334    '$time_source_file'(File, _, user),
  335    (   clause_property(Ref, file(FromFile)),
  336        clause_property(Ref, line_count(FromLine))
  337    ->  Location = FromFile:FromLine
  338    ;   Location = user
  339    ).
  340property_source_file(includes(Master, Stamp), File) :-
  341    system:'$included'(File, _Line, Master, Stamp).
  342property_source_file(included_in(Master, Line), File) :-
  343    system:'$included'(Master, Line, File, _).
  344property_source_file(derived_from(DerivedFrom, Stamp), File) :-
  345    system:'$derived_source'(File, DerivedFrom, Stamp).
  346property_source_file(reloading, File) :-
  347    source_file(File),
  348    '$source_file_property'(File, reloading, true).
  349property_source_file(load_count(Count), File) :-
  350    source_file(File),
  351    '$source_file_property'(File, load_count, Count).
  352property_source_file(number_of_clauses(Count), File) :-
  353    source_file(File),
  354    '$source_file_property'(File, number_of_clauses, Count).
 canonical_source_file(+Spec, -File) is semidet
File is the canonical representation of the source-file Spec.
  361canonical_source_file(Spec, File) :-
  362    atom(Spec),
  363    '$time_source_file'(Spec, _, _),
  364    !,
  365    File = Spec.
  366canonical_source_file(Spec, File) :-
  367    system:'$included'(_Master, _Line, Spec, _),
  368    !,
  369    File = Spec.
  370canonical_source_file(Spec, File) :-
  371    absolute_file_name(Spec, File,
  372                       [ file_type(source),
  373                         solutions(all),
  374                         file_errors(fail)
  375                       ]),
  376    source_file(File),
  377    !.
 exists_source(+Source) is semidet
 exists_source(+Source, -Path) is semidet
True if Source (a term valid for load_files/2) exists. Fails without error if this is not the case. The predicate is intended to be used with :- if, as in the example below. See also source_exports/2.
:- if(exists_source(library(error))).
:- use_module_library(error).
:- endif.
  394exists_source(Source) :-
  395    exists_source(Source, _Path).
  396
  397exists_source(Source, Path) :-
  398    absolute_file_name(Source, Path,
  399                       [ file_type(prolog),
  400                         access(read),
  401                         file_errors(fail)
  402                       ]).
 prolog_load_context(+Key, -Value)
Provides context information for term_expansion and directives. Note that only the line-number info is valid for the '$stream_position'. Largely Quintus compatible.
  411prolog_load_context(module, Module) :-
  412    '$current_source_module'(Module).
  413prolog_load_context(file, File) :-
  414    input_file(File).
  415prolog_load_context(source, F) :-       % SICStus compatibility
  416    input_file(F0),
  417    '$input_context'(Context),
  418    '$top_file'(Context, F0, F).
  419prolog_load_context(stream, S) :-
  420    (   system:'$load_input'(_, S0)
  421    ->  S = S0
  422    ).
  423prolog_load_context(directory, D) :-
  424    input_file(F),
  425    file_directory_name(F, D).
  426prolog_load_context(dialect, D) :-
  427    current_prolog_flag(emulated_dialect, D).
  428prolog_load_context(term_position, TermPos) :-
  429    source_location(_, L),
  430    (   nb_current('$term_position', Pos),
  431        compound(Pos),              % actually set
  432        stream_position_data(line_count, Pos, L)
  433    ->  TermPos = Pos
  434    ;   TermPos = '$stream_position'(0,L,0,0)
  435    ).
  436prolog_load_context(script, Bool) :-
  437    (   '$toplevel':loaded_init_file(script, Path),
  438        input_file(File),
  439        same_file(File, Path)
  440    ->  Bool = true
  441    ;   Bool = false
  442    ).
  443prolog_load_context(variable_names, Bindings) :-
  444    (   nb_current('$variable_names', Bindings0)
  445    ->  Bindings = Bindings0
  446    ;   Bindings = []
  447    ).
  448prolog_load_context(term, Term) :-
  449    nb_current('$term', Term).
  450prolog_load_context(reloading, true) :-
  451    prolog_load_context(source, F),
  452    '$source_file_property'(F, reloading, true).
  453
  454input_file(File) :-
  455    (   system:'$load_input'(_, Stream)
  456    ->  stream_property(Stream, file_name(File))
  457    ),
  458    !.
  459input_file(File) :-
  460    source_location(File, _).
 unload_file(+File) is det
Remove all traces of loading file. If the file is a module file and used use_foreign_library/1,2 to load foreign extensions, these are removed first.
To be done
- Should we introduce a counterpart for initialization/1 that is called when a file is unloaded?
  472:- dynamic system:'$resolved_source_path'/2.  473
  474unload_file(File) :-
  475    (   canonical_source_file(File, Path)
  476    ->  unload_file_(Path),
  477        '$clear_source_admin'(Path),
  478        garbage_collect_clauses
  479    ;   true
  480    ).
  481
  482:- if(current_prolog_flag(open_shared_object, true)).  483unload_file_(Path) :-
  484    source_file_property(Path, module(M)),
  485    ensure_shlib,
  486    !,
  487    forall(shlib:foreign_library_property(Foreign, module(M)),
  488           shlib:unload_foreign_library(Foreign)),
  489    '$unload_file'(Path).
  490:- endif.  491unload_file_(Path) :-
  492    '$unload_file'(Path).
  493
  494:- if(current_prolog_flag(open_shared_object, true)).  495
  496		 /*******************************
  497		 *      FOREIGN LIBRARIES	*
  498		 *******************************/
 use_foreign_library(+FileSpec) is det
 use_foreign_library(+FileSpec, +Entry:atom) is det
Load and install a foreign library as load_foreign_library/1,2 and register the installation using initialization/2 with the option now. This is similar to using:
:- initialization(load_foreign_library(foreign(mylib))).

but using the initialization/1 wrapper causes the library to be loaded after loading of the file in which it appears is completed, while use_foreign_library/1 loads the library immediately. I.e. the difference is only relevant if the remainder of the file uses functionality of the C-library.

  517:- meta_predicate
  518    use_foreign_library(:),
  519    use_foreign_library(:, +).  520:- public
  521    use_foreign_library_noi/1.  522
  523use_foreign_library(FileSpec) :-
  524    ensure_shlib,
  525    initialization(use_foreign_library_noi(FileSpec), now).
  526
  527% noi -> no initialize; used by '$autoload':exports/3.
  528use_foreign_library_noi(FileSpec) :-
  529    ensure_shlib,
  530    shlib:load_foreign_library(FileSpec).
  531
  532use_foreign_library(FileSpec, Options) :-
  533    ensure_shlib,
  534    initialization(shlib:load_foreign_library(FileSpec, Options), now).
  535
  536ensure_shlib :-
  537    '$get_predicate_attribute'(shlib:load_foreign_library(_), defined, 1),
  538    '$get_predicate_attribute'(shlib:load_foreign_library(_,_), defined, 1),
  539    !.
  540ensure_shlib :-
  541    use_module(library(shlib), []).
  542
  543:- export(use_foreign_library/1).  544:- export(use_foreign_library/2).  545
  546:- elif(current_predicate('$activate_static_extension'/1)).  547
  548% Version when using shared objects is disabled and extensions are added
  549% as static libraries.
  550
  551:- meta_predicate
  552    use_foreign_library(:).  553:- public
  554    use_foreign_library_noi/1.  555:- dynamic
  556    loading/1,
  557    foreign_predicate/2.  558
  559use_foreign_library(FileSpec) :-
  560    initialization(use_foreign_library_noi(FileSpec), now).
  561
  562use_foreign_library_noi(Module:foreign(Extension)) :-
  563    setup_call_cleanup(
  564        asserta(loading(foreign(Extension)), Ref),
  565        @('$activate_static_extension'(Extension), Module),
  566        erase(Ref)).
  567
  568:- export(use_foreign_library/1).  569
  570system:'$foreign_registered'(M, H) :-
  571    (   loading(Lib)
  572    ->  true
  573    ;   Lib = '<spontaneous>'
  574    ),
  575    assert(foreign_predicate(Lib, M:H)).
 current_foreign_library(?File, -Public)
Query currently loaded shared libraries.
  581current_foreign_library(File, Public) :-
  582    setof(Pred, foreign_predicate(File, Pred), Public).
  583
  584:- export(current_foreign_library/2).  585
  586:- endif. /* open_shared_object support */
  587
  588                 /*******************************
  589                 *            STREAMS           *
  590                 *******************************/
 stream_position_data(?Field, +Pos, ?Date)
Extract values from stream position objects. '$stream_position' is of the format '$stream_position'(Byte, Char, Line, LinePos)
  597stream_position_data(Prop, Term, Value) :-
  598    nonvar(Prop),
  599    !,
  600    (   stream_position_field(Prop, Pos)
  601    ->  arg(Pos, Term, Value)
  602    ;   throw(error(domain_error(stream_position_data, Prop)))
  603    ).
  604stream_position_data(Prop, Term, Value) :-
  605    stream_position_field(Prop, Pos),
  606    arg(Pos, Term, Value).
  607
  608stream_position_field(char_count,    1).
  609stream_position_field(line_count,    2).
  610stream_position_field(line_position, 3).
  611stream_position_field(byte_count,    4).
  612
  613
  614                 /*******************************
  615                 *            CONTROL           *
  616                 *******************************/
 call_with_depth_limit(:Goal, +DepthLimit, -Result)
Try to proof Goal, but fail on any branch exceeding the indicated depth-limit. Unify Result with the maximum-reached limit on success, depth_limit_exceeded if the limit was exceeded and fails otherwise.
  624:- meta_predicate
  625    call_with_depth_limit(0, +, -).  626
  627call_with_depth_limit(G, Limit, Result) :-
  628    '$depth_limit'(Limit, OLimit, OReached),
  629    (   catch(G, E, '$depth_limit_except'(OLimit, OReached, E)),
  630        '$depth_limit_true'(Limit, OLimit, OReached, Result, Det),
  631        ( Det == ! -> ! ; true )
  632    ;   '$depth_limit_false'(OLimit, OReached, Result)
  633    ).
 call_with_inference_limit(:Goal, +InferenceLimit, -Result)
Equivalent to call(Goal), but poses a limit on the number of inferences. If this limit is reached, Result is unified with inference_limit_exceeded, otherwise Result is unified with ! if Goal succeeded without a choicepoint and true otherwise.

Note that we perform calls in system to avoid auto-importing, which makes raiseInferenceLimitException() fail to recognise that the exception happens in the overhead.

  646:- meta_predicate
  647    call_with_inference_limit(0, +, -).  648
  649call_with_inference_limit(G, Limit, Result) :-
  650    '$inference_limit'(Limit, OLimit),
  651    (   catch(G, Except,
  652              system:'$inference_limit_except'(OLimit, Except, Result0)),
  653        (   Result0 == inference_limit_exceeded
  654        ->  !
  655        ;   system:'$inference_limit_true'(Limit, OLimit, Result0),
  656            ( Result0 == ! -> ! ; true )
  657        ),
  658        Result = Result0
  659    ;   system:'$inference_limit_false'(OLimit)
  660    ).
  661
  662
  663                /********************************
  664                *           DATA BASE           *
  665                *********************************/
  666
  667/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  668The predicate current_predicate/2 is   a  difficult subject since  the
  669introduction  of defaulting     modules   and   dynamic     libraries.
  670current_predicate/2 is normally  called with instantiated arguments to
  671verify some  predicate can   be called without trapping   an undefined
  672predicate.  In this case we must  perform the search algorithm used by
  673the prolog system itself.
  674
  675If the pattern is not fully specified, we only generate the predicates
  676actually available in this  module.   This seems the best for listing,
  677etc.
  678- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  679
  680
  681:- meta_predicate
  682    current_predicate(?, :),
  683    '$defined_predicate'(:).  684
  685current_predicate(Name, Module:Head) :-
  686    (var(Module) ; var(Head)),
  687    !,
  688    generate_current_predicate(Name, Module, Head).
  689current_predicate(Name, Term) :-
  690    '$c_current_predicate'(Name, Term),
  691    '$defined_predicate'(Term),
  692    !.
  693current_predicate(Name, Module:Head) :-
  694    default_module(Module, DefModule),
  695    '$c_current_predicate'(Name, DefModule:Head),
  696    '$defined_predicate'(DefModule:Head),
  697    !.
  698current_predicate(Name, Module:Head) :-
  699    '$autoload':autoload_in(Module, general),
  700    \+ current_prolog_flag(Module:unknown, fail),
  701    (   compound(Head)
  702    ->  compound_name_arity(Head, Name, Arity)
  703    ;   Name = Head, Arity = 0
  704    ),
  705    '$find_library'(Module, Name, Arity, _LoadModule, _Library),
  706    !.
  707
  708generate_current_predicate(Name, Module, Head) :-
  709    current_module(Module),
  710    QHead = Module:Head,
  711    '$c_current_predicate'(Name, QHead),
  712    '$get_predicate_attribute'(QHead, defined, 1).
  713
  714'$defined_predicate'(Head) :-
  715    '$get_predicate_attribute'(Head, defined, 1),
  716    !.
 predicate_property(?Predicate, ?Property) is nondet
True when Property is a property of Predicate.
  722:- meta_predicate
  723    predicate_property(:, ?).  724
  725:- multifile
  726    '$predicate_property'/2.  727
  728:- '$iso'(predicate_property/2).  729
  730predicate_property(Pred, Property) :-           % Mode ?,+
  731    nonvar(Property),
  732    !,
  733    property_predicate(Property, Pred).
  734predicate_property(Pred, Property) :-           % Mode +,-
  735    define_or_generate(Pred),
  736    '$predicate_property'(Property, Pred).
 property_predicate(+Property, ?Pred)
First handle the special cases that are not about querying normally defined predicates: undefined, visible and autoload, followed by the generic case.
  744property_predicate(undefined, Pred) :-
  745    !,
  746    Pred = Module:Head,
  747    current_module(Module),
  748    '$c_current_predicate'(_, Pred),
  749    \+ '$defined_predicate'(Pred),          % Speed up a bit
  750    \+ current_predicate(_, Pred),
  751    goal_name_arity(Head, Name, Arity),
  752    \+ system_undefined(Module:Name/Arity).
  753property_predicate(visible, Pred) :-
  754    !,
  755    visible_predicate(Pred).
  756property_predicate(autoload(File), Head) :-
  757    !,
  758    \+ current_prolog_flag(autoload, false),
  759    '$autoload':autoloadable(Head, File).
  760property_predicate(implementation_module(IM), M:Head) :-
  761    !,
  762    atom(M),
  763    (   default_module(M, DM),
  764        '$get_predicate_attribute'(DM:Head, defined, 1)
  765    ->  (   '$get_predicate_attribute'(DM:Head, imported, ImportM)
  766        ->  IM = ImportM
  767        ;   IM = M
  768        )
  769    ;   \+ current_prolog_flag(M:unknown, fail),
  770        goal_name_arity(Head, Name, Arity),
  771        '$find_library'(_, Name, Arity, LoadModule, _File)
  772    ->  IM = LoadModule
  773    ;   M = IM
  774    ).
  775property_predicate(iso, _:Head) :-
  776    callable(Head),
  777    !,
  778    goal_name_arity(Head, Name, Arity),
  779    current_predicate(system:Name/Arity),
  780    '$predicate_property'(iso, system:Head).
  781property_predicate(built_in, Module:Head) :-
  782    callable(Head),
  783    !,
  784    goal_name_arity(Head, Name, Arity),
  785    current_predicate(Module:Name/Arity),
  786    '$predicate_property'(built_in, Module:Head).
  787property_predicate(Property, Pred) :-
  788    define_or_generate(Pred),
  789    '$predicate_property'(Property, Pred).
  790
  791goal_name_arity(Head, Name, Arity) :-
  792    compound(Head),
  793    !,
  794    compound_name_arity(Head, Name, Arity).
  795goal_name_arity(Head, Head, 0).
 define_or_generate(+Head) is semidet
define_or_generate(-Head) is nondet
If the predicate is known, try to resolve it. Otherwise generate the known predicate, but do not try to (auto)load the predicate.
  804define_or_generate(M:Head) :-
  805    callable(Head),
  806    atom(M),
  807    '$get_predicate_attribute'(M:Head, defined, 1),
  808    !.
  809define_or_generate(M:Head) :-
  810    callable(Head),
  811    nonvar(M), M \== system,
  812    !,
  813    '$define_predicate'(M:Head).
  814define_or_generate(Pred) :-
  815    current_predicate(_, Pred),
  816    '$define_predicate'(Pred).
  817
  818
  819'$predicate_property'(interpreted, Pred) :-
  820    '$get_predicate_attribute'(Pred, foreign, 0).
  821'$predicate_property'(visible, Pred) :-
  822    '$get_predicate_attribute'(Pred, defined, 1).
  823'$predicate_property'(built_in, Pred) :-
  824    '$get_predicate_attribute'(Pred, system, 1).
  825'$predicate_property'(exported, Pred) :-
  826    '$get_predicate_attribute'(Pred, exported, 1).
  827'$predicate_property'(public, Pred) :-
  828    '$get_predicate_attribute'(Pred, public, 1).
  829'$predicate_property'(non_terminal, Pred) :-
  830    '$get_predicate_attribute'(Pred, non_terminal, 1).
  831'$predicate_property'(foreign, Pred) :-
  832    '$get_predicate_attribute'(Pred, foreign, 1).
  833'$predicate_property'((dynamic), Pred) :-
  834    '$get_predicate_attribute'(Pred, (dynamic), 1).
  835'$predicate_property'((static), Pred) :-
  836    '$get_predicate_attribute'(Pred, (dynamic), 0).
  837'$predicate_property'((volatile), Pred) :-
  838    '$get_predicate_attribute'(Pred, (volatile), 1).
  839'$predicate_property'((thread_local), Pred) :-
  840    '$get_predicate_attribute'(Pred, (thread_local), 1).
  841'$predicate_property'((multifile), Pred) :-
  842    '$get_predicate_attribute'(Pred, (multifile), 1).
  843'$predicate_property'((discontiguous), Pred) :-
  844    '$get_predicate_attribute'(Pred, (discontiguous), 1).
  845'$predicate_property'(imported_from(Module), Pred) :-
  846    '$get_predicate_attribute'(Pred, imported, Module).
  847'$predicate_property'(transparent, Pred) :-
  848    '$get_predicate_attribute'(Pred, transparent, 1).
  849'$predicate_property'(meta_predicate(Pattern), Pred) :-
  850    '$get_predicate_attribute'(Pred, transparent, 1),
  851    '$get_predicate_attribute'(Pred, meta_predicate, Pattern).
  852'$predicate_property'(mode(Pattern), Pred) :-
  853    '$get_predicate_attribute'(Pred, transparent, 0),
  854    '$get_predicate_attribute'(Pred, meta_predicate, Pattern).
  855'$predicate_property'(file(File), Pred) :-
  856    '$get_predicate_attribute'(Pred, file, File).
  857'$predicate_property'(line_count(LineNumber), Pred) :-
  858    '$get_predicate_attribute'(Pred, line_count, LineNumber).
  859'$predicate_property'(notrace, Pred) :-
  860    '$get_predicate_attribute'(Pred, trace, 0).
  861'$predicate_property'(nodebug, Pred) :-
  862    '$get_predicate_attribute'(Pred, hide_childs, 1).
  863'$predicate_property'(spying, Pred) :-
  864    '$get_predicate_attribute'(Pred, spy, 1).
  865'$predicate_property'(number_of_clauses(N), Pred) :-
  866    '$get_predicate_attribute'(Pred, number_of_clauses, N).
  867'$predicate_property'(number_of_rules(N), Pred) :-
  868    '$get_predicate_attribute'(Pred, number_of_rules, N).
  869'$predicate_property'(last_modified_generation(Gen), Pred) :-
  870    '$get_predicate_attribute'(Pred, last_modified_generation, Gen).
  871'$predicate_property'(indexed(Indices), Pred) :-
  872    '$get_predicate_attribute'(Pred, indexed, Indices).
  873'$predicate_property'(noprofile, Pred) :-
  874    '$get_predicate_attribute'(Pred, noprofile, 1).
  875'$predicate_property'(ssu, Pred) :-
  876    '$get_predicate_attribute'(Pred, ssu, 1).
  877'$predicate_property'(iso, Pred) :-
  878    '$get_predicate_attribute'(Pred, iso, 1).
  879'$predicate_property'(det, Pred) :-
  880    '$get_predicate_attribute'(Pred, det, 1).
  881'$predicate_property'(sig_atomic, Pred) :-
  882    '$get_predicate_attribute'(Pred, sig_atomic, 1).
  883'$predicate_property'(quasi_quotation_syntax, Pred) :-
  884    '$get_predicate_attribute'(Pred, quasi_quotation_syntax, 1).
  885'$predicate_property'(defined, Pred) :-
  886    '$get_predicate_attribute'(Pred, defined, 1).
  887'$predicate_property'(tabled, Pred) :-
  888    '$get_predicate_attribute'(Pred, tabled, 1).
  889'$predicate_property'(tabled(Flag), Pred) :-
  890    '$get_predicate_attribute'(Pred, tabled, 1),
  891    table_flag(Flag, Pred).
  892'$predicate_property'(incremental, Pred) :-
  893    '$get_predicate_attribute'(Pred, incremental, 1).
  894'$predicate_property'(monotonic, Pred) :-
  895    '$get_predicate_attribute'(Pred, monotonic, 1).
  896'$predicate_property'(opaque, Pred) :-
  897    '$get_predicate_attribute'(Pred, opaque, 1).
  898'$predicate_property'(lazy, Pred) :-
  899    '$get_predicate_attribute'(Pred, lazy, 1).
  900'$predicate_property'(abstract(N), Pred) :-
  901    '$get_predicate_attribute'(Pred, abstract, N).
  902'$predicate_property'(size(Bytes), Pred) :-
  903    '$get_predicate_attribute'(Pred, size, Bytes).
  904'$predicate_property'(primary_index(Arg), Pred) :-
  905    '$get_predicate_attribute'(Pred, primary_index, Arg).
  906
  907system_undefined(user:prolog_trace_interception/4).
  908system_undefined(prolog:prolog_exception_hook/5).
  909system_undefined(system:'$c_call_prolog'/0).
  910system_undefined(system:window_title/2).
  911
  912table_flag(variant, Pred) :-
  913    '$tbl_implementation'(Pred, M:Head),
  914    M:'$tabled'(Head, variant).
  915table_flag(subsumptive, Pred) :-
  916    '$tbl_implementation'(Pred, M:Head),
  917    M:'$tabled'(Head, subsumptive).
  918table_flag(shared, Pred) :-
  919    '$get_predicate_attribute'(Pred, tshared, 1).
  920table_flag(incremental, Pred) :-
  921    '$get_predicate_attribute'(Pred, incremental, 1).
  922table_flag(monotonic, Pred) :-
  923    '$get_predicate_attribute'(Pred, monotonic, 1).
  924table_flag(subgoal_abstract(N), Pred) :-
  925    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  926table_flag(answer_abstract(N), Pred) :-
  927    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  928table_flag(subgoal_abstract(N), Pred) :-
  929    '$get_predicate_attribute'(Pred, max_answers, N).
 visible_predicate(:Head) is nondet
True when Head can be called without raising an existence error. This implies it is defined, can be inherited from a default module or can be autoloaded.
  938visible_predicate(Pred) :-
  939    Pred = M:Head,
  940    current_module(M),
  941    (   callable(Head)
  942    ->  (   '$get_predicate_attribute'(Pred, defined, 1)
  943        ->  true
  944        ;   \+ current_prolog_flag(M:unknown, fail),
  945            '$head_name_arity'(Head, Name, Arity),
  946            '$find_library'(M, Name, Arity, _LoadModule, _Library)
  947        )
  948    ;   setof(PI, visible_in_module(M, PI), PIs),
  949        '$member'(Name/Arity, PIs),
  950        functor(Head, Name, Arity)
  951    ).
  952
  953visible_in_module(M, Name/Arity) :-
  954    default_module(M, DefM),
  955    DefHead = DefM:Head,
  956    '$c_current_predicate'(_, DefHead),
  957    '$get_predicate_attribute'(DefHead, defined, 1),
  958    \+ hidden_system_predicate(Head),
  959    functor(Head, Name, Arity).
  960visible_in_module(_, Name/Arity) :-
  961    '$in_library'(Name, Arity, _).
  962
  963hidden_system_predicate(Head) :-
  964    functor(Head, Name, _),
  965    atom(Name),                     % Avoid [].
  966    sub_atom(Name, 0, _, _, $),
  967    \+ current_prolog_flag(access_level, system).
  968
  969
  970                /********************************
  971                *      SOURCE LOCATION          *
  972                *********************************/
 $predicate_source_location(:Head, -Location) is semidet
Location is File:Line, the place where the predicate Head is defined. Head is resolved to its primary definition, i.e., imported predicates are traced back to the module that defines them. For predicates defined in C, the location of the C function that implements it is used. See '$foreign_predicate_source'/2.

This predicate provides the source location for both the message system (see predicate_reference//2 in boot/messages.pl) and library(edit).

  986:- meta_predicate
  987    '$predicate_source_location'(:, -).  988
  989'$predicate_source_location'(Head, File:Line) :-
  990    '$primary_predicate'(Head, Primary),
  991    (   predicate_property(Primary, file(File)),
  992        predicate_property(Primary, line_count(Line))
  993    ->  true
  994    ;   predicate_property(Primary, foreign),
  995        '$foreign_source_location'(Primary, File, Line)
  996    ).
 $primary_predicate(:Head, -Primary) is det
Primary is the module qualified Head in the module that defines the predicate rather than one that imports it.
 1003'$primary_predicate'(Pred, Primary) :-
 1004    (   predicate_property(Pred, imported_from(Module))
 1005    ->  strip_module(Pred, _, Head),
 1006        Primary = Module:Head
 1007    ;   Primary = Pred
 1008    ).
 $foreign_source_location(:Head, -File, -Line) is semidet
Source location of a foreign (C defined) predicate. As this is resolved by running addr2line or atos in a child process we can only afford to do this once per predicate.
 1016:- dynamic
 1017    '$foreign_source_cache'/2.              % PI, File:Line or `none`
 1018
 1019'$foreign_source_location'(Head, File, Line) :-
 1020    '$pi_head'(PI, Head),
 1021    (   '$foreign_source_cache'(PI, Cached)
 1022    ->  true
 1023    ;   (   '$foreign_predicate_source'(Head, Source),
 1024            '$addr2line_location'(Source, File0, Line0)
 1025        ->  Cached = File0:Line0
 1026        ;   Cached = none
 1027        ),
 1028        assertz('$foreign_source_cache'(PI, Cached))
 1029    ),
 1030    Cached = File:Line.
 $addr2line_location(+Description, -File, -Line) is semidet
Parse the Function() at File:Line description as produced by '$foreign_predicate_source'/2 and '$addr2line'/2. Fails if the description does not carry a source location, which happens if the symbol lives in the main executable or the file has no debug information.
 1040'$addr2line_location'(Description, File, Line) :-
 1041    sub_string(Description, Before, _, After, " at "),
 1042    !,
 1043    Start is Before+4,
 1044    sub_string(Description, Start, After, 0, Rest),
 1045    '$split_file_line'(Rest, File, Line).
 1046
 1047'$split_file_line'(Rest, File, Line) :-
 1048    sub_string(Rest, BC, _, AC, ":"),
 1049    Start is BC+1,
 1050    sub_string(Rest, Start, AC, 0, Tail),
 1051    (   sub_string(Tail, BS, _, _, " ")      % e.g. " (discriminator 1)"
 1052    ->  sub_string(Tail, 0, BS, _, LineText)
 1053    ;   LineText = Tail
 1054    ),
 1055    number_string(Line, LineText),
 1056    integer(Line),
 1057    Line >= 1,                               % `addr2line` says 0 if unknown
 1058    !,
 1059    sub_string(Rest, 0, BC, _, FileText),
 1060    FileText \== "??",                       % and `??` for the file
 1061    atom_string(File, FileText).
 clause_property(+ClauseRef, ?Property) is nondet
Provide information on individual clauses. Defined properties are:
line_count(-Line)
Line from which the clause is loaded.
file(-File)
File from which the clause is loaded.
source(-File)
File that `owns' the clause: reloading this file wipes the clause.
fact
Clause has body true.
erased
Clause was erased.
predicate(:PI)
Predicate indicator of the predicate this clause belongs to. Can be used to find the predicate of erased clauses.
module(-M)
Module context in which the clause was compiled.
 1086clause_property(Clause, Property) :-
 1087    '$clause_property'(Property, Clause).
 1088
 1089'$clause_property'(line_count(LineNumber), Clause) :-
 1090    '$get_clause_attribute'(Clause, line_count, LineNumber).
 1091'$clause_property'(file(File), Clause) :-
 1092    '$get_clause_attribute'(Clause, file, File).
 1093'$clause_property'(source(File), Clause) :-
 1094    '$get_clause_attribute'(Clause, owner, File).
 1095'$clause_property'(size(Bytes), Clause) :-
 1096    '$get_clause_attribute'(Clause, size, Bytes).
 1097'$clause_property'(fact, Clause) :-
 1098    '$get_clause_attribute'(Clause, fact, true).
 1099'$clause_property'(erased, Clause) :-
 1100    '$get_clause_attribute'(Clause, erased, true).
 1101'$clause_property'(predicate(PI), Clause) :-
 1102    '$get_clause_attribute'(Clause, predicate_indicator, PI).
 1103'$clause_property'(module(M), Clause) :-
 1104    '$get_clause_attribute'(Clause, module, M).
 dynamic(:Predicates, +Options) is det
Define a predicate as dynamic with optionally additional properties. Defined options are:
 1118dynamic(M:Predicates, Options) :-
 1119    '$must_be'(list, Predicates),
 1120    options_properties(Options, Props),
 1121    set_pprops(Predicates, M, [dynamic|Props]).
 1122
 1123set_pprops([], _, _).
 1124set_pprops([H|T], M, Props) :-
 1125    set_pprops1(Props, M:H),
 1126    strip_module(M:H, M2, P),
 1127    '$pi_head'(M2:P, Pred),
 1128    '$set_table_wrappers'(Pred),
 1129    set_pprops(T, M, Props).
 1130
 1131set_pprops1([], _).
 1132set_pprops1([H|T], P) :-
 1133    (   atom(H)
 1134    ->  '$set_predicate_attribute'(P, H, true)
 1135    ;   H =.. [Name,Value]
 1136    ->  '$set_predicate_attribute'(P, Name, Value)
 1137    ),
 1138    set_pprops1(T, P).
 1139
 1140options_properties(Options, Props) :-
 1141    G = opt_prop(_,_,_,_),
 1142    findall(G, G, Spec),
 1143    options_properties(Spec, Options, Props).
 1144
 1145options_properties([], _, []).
 1146options_properties([opt_prop(Name, Type, SetValue, Prop)|T],
 1147                   Options, [Prop|PT]) :-
 1148    Opt =.. [Name,V],
 1149    '$option'(Opt, Options),
 1150    '$must_be'(Type, V),
 1151    V = SetValue,
 1152    !,
 1153    options_properties(T, Options, PT).
 1154options_properties([_|T], Options, PT) :-
 1155    options_properties(T, Options, PT).
 1156
 1157opt_prop(incremental,   boolean,               Bool,  incremental(Bool)).
 1158opt_prop(abstract,      between(0,0),          0,     abstract).
 1159opt_prop(multifile,     boolean,               true,  multifile).
 1160opt_prop(discontiguous, boolean,               true,  discontiguous).
 1161opt_prop(volatile,      boolean,               true,  volatile).
 1162opt_prop(thread,        oneof(atom, [local,shared],[local,shared]),
 1163                                               local, thread_local).
 1164
 1165                /********************************
 1166                *            MODULES            *
 1167                *********************************/
 current_module(?Module) is nondet
True if Module is a currently defined module.
 1173current_module(Module) :-
 1174    '$current_module'(Module, _).
 module_property(?Module, ?Property) is nondet
True if Property is a property of Module. Defined properties are:
file(File)
Module is loaded from File.
line_count(Count)
The module declaration is on line Count of File.
exports(ListOfPredicateIndicators)
The module exports ListOfPredicateIndicators
exported_operators(ListOfOp3)
The module exports the operators ListOfOp3.
 1190module_property(Module, Property) :-
 1191    nonvar(Module), nonvar(Property),
 1192    !,
 1193    property_module(Property, Module).
 1194module_property(Module, Property) :-    % -, file(File)
 1195    nonvar(Property), Property = file(File),
 1196    !,
 1197    (   nonvar(File)
 1198    ->  '$current_module'(Modules, File),
 1199        (   atom(Modules)
 1200        ->  Module = Modules
 1201        ;   '$member'(Module, Modules)
 1202        )
 1203    ;   '$current_module'(Module, File),
 1204        File \== []
 1205    ).
 1206module_property(Module, Property) :-
 1207    current_module(Module),
 1208    property_module(Property, Module).
 1209
 1210property_module(Property, Module) :-
 1211    module_property(Property),
 1212    (   Property = exported_operators(List)
 1213    ->  '$exported_ops'(Module, List, [])
 1214    ;   '$module_property'(Module, Property)
 1215    ).
 1216
 1217module_property(class(_)).
 1218module_property(file(_)).
 1219module_property(line_count(_)).
 1220module_property(exports(_)).
 1221module_property(exported_operators(_)).
 1222module_property(size(_)).
 1223module_property(program_size(_)).
 1224module_property(program_space(_)).
 1225module_property(last_modified_generation(_)).
 module(+Module) is det
Set the module that is associated to the toplevel to Module.
 1231module(Module) :-
 1232    atom(Module),
 1233    current_module(Module),
 1234    !,
 1235    '$set_typein_module'(Module).
 1236module(Module) :-
 1237    '$set_typein_module'(Module),
 1238    print_message(warning, no_current_module(Module)).
 working_directory(-Old, +New)
True when Old is the current working directory and the working directory has been updated to New.
 1245working_directory(Old, New) :-
 1246    '$cwd'(Old),
 1247    (   Old == New
 1248    ->  true
 1249    ;   '$chdir'(New)
 1250    ).
 1251
 1252
 1253                 /*******************************
 1254                 *            TRIES             *
 1255                 *******************************/
 current_trie(?Trie) is nondet
True if Trie is the handle of an existing trie.
 1261current_trie(Trie) :-
 1262    current_blob(Trie, trie),
 1263    is_trie(Trie).
 trie_property(?Trie, ?Property)
True when Property is a property of Trie. Defined properties are:
value_count(Count)
Number of terms in the trie.
node_count(Count)
Number of nodes in the trie.
size(Bytes)
Number of bytes needed to store the trie.
hashed(Count)
Number of hashed nodes.
compiled_size(Bytes)
Size of the compiled representation (if the trie is compiled)
lookup_count(Count)
Number of data lookups on the trie
gen_call_count(Count)
Number of trie_gen/2 calls on this trie

Incremental tabling statistics:

invalidated(Count)
Number of times the trie was inivalidated
reevaluated(Count)
Number of times the trie was re-evaluated

Shared tabling statistics:

deadlock(Count)
Number of times the table was involved in a deadlock
wait(Count)
Number of times a thread had to wait for this table
 1299trie_property(Trie, Property) :-
 1300    current_trie(Trie),
 1301    trie_property(Property),
 1302    '$trie_property'(Trie, Property).
 1303
 1304trie_property(node_count(_)).
 1305trie_property(value_count(_)).
 1306trie_property(size(_)).
 1307trie_property(hashed(_)).
 1308trie_property(compiled_size(_)).
 1309                                                % below only when -DO_TRIE_STATS
 1310trie_property(lookup_count(_)).                 % is enabled in pl-trie.h
 1311trie_property(gen_call_count(_)).
 1312trie_property(invalidated(_)).                  % IDG stats
 1313trie_property(reevaluated(_)).
 1314trie_property(deadlock(_)).                     % Shared tabling stats
 1315trie_property(wait(_)).
 1316trie_property(idg_affected_count(_)).
 1317trie_property(idg_dependent_count(_)).
 1318trie_property(idg_size(_)).
 1319
 1320
 1321                /********************************
 1322                *      SYSTEM INTERACTION       *
 1323                *********************************/
 1324
 1325shell(Command) :-
 1326    shell(Command, 0).
 1327
 1328
 1329                 /*******************************
 1330                 *            SIGNALS           *
 1331                 *******************************/
 1332
 1333:- meta_predicate
 1334    on_signal(+, :, :),
 1335    current_signal(?, ?, :).
 on_signal(+Signal, -OldHandler, :NewHandler) is det
 1339on_signal(Signal, Old, New) :-
 1340    atom(Signal),
 1341    !,
 1342    '$on_signal'(_Num, Signal, Old, New).
 1343on_signal(Signal, Old, New) :-
 1344    integer(Signal),
 1345    !,
 1346    '$on_signal'(Signal, _Name, Old, New).
 1347on_signal(Signal, _Old, _New) :-
 1348    '$type_error'(signal_name, Signal).
 current_signal(?Name, ?SignalNumber, :Handler) is nondet
 1352current_signal(Name, Id, Handler) :-
 1353    between(1, 32, Id),
 1354    '$on_signal'(Id, Name, Handler, Handler).
 1355
 1356:- multifile
 1357    prolog:called_by/2. 1358
 1359prolog:called_by(on_signal(_,_,New), [New+1]) :-
 1360    (   new == throw
 1361    ;   new == default
 1362    ), !, fail.
 1363
 1364
 1365                 /*******************************
 1366                 *             I/O              *
 1367                 *******************************/
 1368
 1369format(Fmt) :-
 1370    format(Fmt, []).
 1371
 1372                 /*******************************
 1373                 *            FILES             *
 1374                 *******************************/
 absolute_file_name(+Term, -AbsoluteFile)
 1378absolute_file_name(Name, Abs) :-
 1379    atomic(Name),
 1380    !,
 1381    '$absolute_file_name'(Name, Abs).
 1382absolute_file_name(Term, Abs) :-
 1383    '$chk_file'(Term, [''], [access(read)], true, File),
 1384    !,
 1385    '$absolute_file_name'(File, Abs).
 1386absolute_file_name(Term, Abs) :-
 1387    '$chk_file'(Term, [''], [], true, File),
 1388    !,
 1389    '$absolute_file_name'(File, Abs).
 tmp_file_stream(-File, -Stream, +Options) is det
tmp_file_stream(+Encoding, -File, -Stream) is det
Create a temporary file and open it atomically. The second mode is for compatibility reasons.
 1397tmp_file_stream(Enc, File, Stream) :-
 1398    atom(Enc), var(File), var(Stream),
 1399    !,
 1400    '$tmp_file_stream'('', Enc, File, Stream).
 1401tmp_file_stream(File, Stream, Options) :-
 1402    current_prolog_flag(encoding, DefEnc),
 1403    '$option'(encoding(Enc), Options, DefEnc),
 1404    '$option'(extension(Ext), Options, ''),
 1405    '$tmp_file_stream'(Ext, Enc, File, Stream),
 1406    set_stream(Stream, file_name(File)).
 1407
 1408
 1409                /********************************
 1410                *        MEMORY MANAGEMENT      *
 1411                *********************************/
 garbage_collect is det
Invoke the garbage collector. The argument of the underlying '$garbage_collect'/1 is the debugging level to use during garbage collection. This only works if the system is compiled with the -DODEBUG cpp flag. Only to simplify maintenance.
 1420garbage_collect :-
 1421    '$garbage_collect'(0).
 set_prolog_stack(+Name, +Option) is det
Set a parameter for one of the Prolog stacks.
 1427set_prolog_stack(Stack, Option) :-
 1428    Option =.. [Name,Value0],
 1429    Value is Value0,
 1430    '$set_prolog_stack'(Stack, Name, _Old, Value).
 prolog_stack_property(?Stack, ?Property) is nondet
Examine stack properties.
 1436prolog_stack_property(Stack, Property) :-
 1437    stack_property(P),
 1438    stack_name(Stack),
 1439    Property =.. [P,Value],
 1440    '$set_prolog_stack'(Stack, P, Value, Value).
 1441
 1442stack_name(local).
 1443stack_name(global).
 1444stack_name(trail).
 1445
 1446stack_property(limit).
 1447stack_property(spare).
 1448stack_property(min_free).
 1449stack_property(low).
 1450stack_property(factor).
 1451
 1452
 1453		 /*******************************
 1454		 *            CLAUSE		*
 1455		 *******************************/
 rule(:Head, -Rule) is nondet
 rule(:Head, -Rule, Ref) is nondet
Similar to clause/2,3. but deals with clauses that do not use :- as neck.
 1463rule(Head, Rule) :-
 1464    '$rule'(Head, Rule0),
 1465    conditional_rule(Rule0, Rule1),
 1466    Rule = Rule1.
 1467rule(Head, Rule, Ref) :-
 1468    '$rule'(Head, Rule0, Ref),
 1469    conditional_rule(Rule0, Rule1),
 1470    Rule = Rule1.
 1471
 1472conditional_rule(?=>(Head, (!, Body)), Rule) =>
 1473    Rule = (Head => Body).
 1474conditional_rule(?=>(Head, !), Rule) =>
 1475    Rule = (Head => true).
 1476conditional_rule(?=>(Head, Body0), Rule),
 1477    split_on_cut(Body0, Cond, Body) =>
 1478    Rule = (Head,Cond=>Body).
 1479conditional_rule(Head, Rule) =>
 1480    Rule = Head.
 1481
 1482split_on_cut((Cond0,!,Body0), Cond, Body) =>
 1483    Cond = Cond0,
 1484    Body = Body0.
 1485split_on_cut((!,Body0), Cond, Body) =>
 1486    Cond = true,
 1487    Body = Body0.
 1488split_on_cut((A,B), Cond, Body) =>
 1489    Cond = (A,Cond1),
 1490    split_on_cut(B, Cond1, Body).
 1491split_on_cut(_, _, _) =>
 1492    fail.
 1493
 1494
 1495                 /*******************************
 1496                 *             TERM             *
 1497                 *******************************/
 1498
 1499:- '$iso'((numbervars/3)).
 numbervars(+Term, +StartIndex, -EndIndex) is det
Number all unbound variables in Term using '$VAR'(N), where the first N is StartIndex and EndIndex is unified to the index that will be given to the next variable.
 1507numbervars(Term, From, To) :-
 1508    numbervars(Term, From, To, []).
 1509
 1510
 1511                 /*******************************
 1512                 *            STRING            *
 1513                 *******************************/
 term_string(?Term, ?String, +Options)
Parse/write a term from/to a string using Options.
 1519term_string(Term, String, Options) :-
 1520    nonvar(String),
 1521    !,
 1522    read_term_from_atom(String, Term, Options).
 1523term_string(Term, String, Options) :-
 1524    (   '$option'(quoted(_), Options)
 1525    ->  Options1 = Options
 1526    ;   '$merge_options'(_{quoted:true}, Options, Options1)
 1527    ),
 1528    format(string(String), '~W', [Term, Options1]).
 1529
 1530
 1531		 /*******************************
 1532		 *            THREADS		*
 1533		 *******************************/
 1534
 1535:- meta_predicate
 1536    thread_create(0, -).
 thread_create(:Goal, -Id)
Shorthand for thread_create(Goal, Id, []).
 1542thread_create(Goal, Id) :-
 1543    thread_create(Goal, Id, []).
 thread_join(+Id)
Join a thread and raise an error of the thread did not succeed.
Errors
- thread_error(Status), where Status is the result of thread_join/2.
 1552thread_join(Id) :-
 1553    thread_join(Id, Status),
 1554    (   Status == true
 1555    ->  true
 1556    ;   throw(error(thread_error(Id, Status), _))
 1557    ).
 sig_block(:Pattern) is det
Block thread signals that unify with Pattern.
 sig_unblock(:Pattern) is det
Remove any signal block that is more specific than Pattern.
 1567sig_block(Pattern) :-
 1568    (   nb_current('$sig_blocked', List)
 1569    ->  true
 1570    ;   List = []
 1571    ),
 1572    nb_setval('$sig_blocked', [Pattern|List]).
 1573
 1574sig_unblock(Pattern) :-
 1575    (   nb_current('$sig_blocked', List)
 1576    ->  unblock(List, Pattern, NewList),
 1577        (   List == NewList
 1578        ->  true
 1579        ;   nb_setval('$sig_blocked', NewList),
 1580            '$sig_unblock'
 1581        )
 1582    ;   true
 1583    ).
 1584
 1585unblock([], _, []).
 1586unblock([H|T], P, List) :-
 1587    (   subsumes_term(P, H)
 1588    ->  unblock(T, P, List)
 1589    ;   List = [H|T1],
 1590        unblock(T, P, T1)
 1591    ).
 1592
 1593:- public signal_is_blocked/1.          % called by signal_is_blocked()
 1594
 1595signal_is_blocked(Head) :-
 1596    nb_current('$sig_blocked', List),
 1597    memberchk(Head, List).
 set_prolog_gc_thread(+Status)
Control the GC thread. Status is one of
false
Disable the separate GC thread, running atom and clause garbage collection in the triggering thread.
true
Enable the separate GC thread. All implicit atom and clause garbage collection is executed by the thread gc.
stop
Stop the gc thread if it is running. The thread is recreated on the next implicit atom or clause garbage collection. Used by fork/1 to avoid forking a multi-threaded application.
 1614set_prolog_gc_thread(Status) :-
 1615    var(Status),
 1616    !,
 1617    '$instantiation_error'(Status).
 1618set_prolog_gc_thread(_) :-
 1619    \+ current_prolog_flag(threads, true),
 1620    !.
 1621set_prolog_gc_thread(false) :-
 1622    !,
 1623    set_prolog_flag(gc_thread, false),
 1624    (   current_prolog_flag(threads, true)
 1625    ->  (   '$gc_stop'
 1626        ->  thread_join(gc)
 1627        ;   true
 1628        )
 1629    ;   true
 1630    ).
 1631set_prolog_gc_thread(true) :-
 1632    !,
 1633    set_prolog_flag(gc_thread, true).
 1634set_prolog_gc_thread(stop) :-
 1635    !,
 1636    (   current_prolog_flag(threads, true)
 1637    ->  (   '$gc_stop'
 1638        ->  thread_join(gc)
 1639        ;   true
 1640        )
 1641    ;   true
 1642    ).
 1643set_prolog_gc_thread(Status) :-
 1644    '$domain_error'(gc_thread, Status).
 transaction(:Goal)
 transaction(:Goal, +Options)
 transaction(:Goal, :Constraint, +Mutex)
 snapshot(:Goal)
Wrappers to guarantee clean Module:Goal terms.
 1653transaction(Goal) :-
 1654    '$transaction'(Goal, []).
 1655transaction(Goal, Options) :-
 1656    '$transaction'(Goal, Options).
 1657transaction(Goal, Constraint, Mutex) :-
 1658    '$transaction'(Goal, Constraint, Mutex).
 1659snapshot(Goal) :-
 1660    '$snapshot'(Goal).
 1661
 1662
 1663		 /*******************************
 1664		 *            UNDO		*
 1665		 *******************************/
 1666
 1667:- meta_predicate
 1668    undo(0).
 undo(:Goal)
Schedule Goal to be called when backtracking takes us back to before this call.
 1675undo(Goal) :-
 1676    '$undo'(Goal).
 1677
 1678:- public
 1679    '$run_undo'/1. 1680
 1681'$run_undo'([One]) :-
 1682    !,
 1683    (   call(One)
 1684    ->  true
 1685    ;   true
 1686    ).
 1687'$run_undo'(List) :-
 1688    run_undo(List, _, Error),
 1689    (   var(Error)
 1690    ->  true
 1691    ;   throw(Error)
 1692    ).
 1693
 1694run_undo([], E, E).
 1695run_undo([H|T], E0, E) :-
 1696    (   catch(H, E1, true)
 1697    ->  (   var(E1)
 1698        ->  true
 1699        ;   '$urgent_exception'(E0, E1, E2)
 1700        )
 1701    ;   true
 1702    ),
 1703    run_undo(T, E2, E).
 $wrap_predicate(:Head, +Name, -Closure, -Wrapped, :Body) is det
Would be nicer to have this from library(prolog_wrap), but we need it for tabling, so it must be a system predicate.
 1711:- meta_predicate
 1712    '$wrap_predicate'(:, +, -, -, 0). 1713
 1714'$wrap_predicate'(M:Head, WName, Closure, call(Wrapped), Body) :-
 1715    callable_name_arguments(Head, PName, Args),
 1716    callable_name_arity(Head, PName, Arity),
 1717    (   is_most_general_term(Head)
 1718    ->  true
 1719    ;   '$domain_error'(most_general_term, Head)
 1720    ),
 1721    atomic_list_concat(['$wrap$', PName], WrapName),
 1722    PI = M:WrapName/Arity,
 1723    dynamic(PI),
 1724    '$notransact'(PI),
 1725    volatile(PI),
 1726    module_transparent(PI),
 1727    WHead =.. [WrapName|Args],
 1728    wrapped_clause(M, WHead, Body, Clause),
 1729    '$c_wrap_predicate'(M:Head, WName, Closure, Wrapped, Clause).
 1730
 1731callable_name_arguments(Head, PName, Args) :-
 1732    atom(Head),
 1733    !,
 1734    PName = Head,
 1735    Args = [].
 1736callable_name_arguments(Head, PName, Args) :-
 1737    compound_name_arguments(Head, PName, Args).
 1738
 1739callable_name_arity(Head, PName, Arity) :-
 1740    atom(Head),
 1741    !,
 1742    PName = Head,
 1743    Arity = 0.
 1744callable_name_arity(Head, PName, Arity) :-
 1745    compound_name_arity(Head, PName, Arity).
 1746
 1747wrapped_clause(M, WHead, M:Body, M:(WHead :- Body)) :- !.
 1748wrapped_clause(M, WHead, MB:Body, M:(WHead :- MB:Body))