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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)  1985-2020, University of Amsterdam
    7                              VU University Amsterdam
    8                              CWI, Amsterdam
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module('$syspreds',
   38          [ leash/1,
   39            visible/1,
   40            style_check/1,
   41            (spy)/1,
   42            (nospy)/1,
   43            nospyall/0,
   44            debugging/0,
   45            flag/3,
   46            atom_prefix/2,
   47            dwim_match/2,
   48            source_file_property/2,
   49            source_file/1,
   50            source_file/2,
   51            unload_file/1,
   52            exists_source/1,                    % +Spec
   53            exists_source/2,                    % +Spec, -Path
   54            use_foreign_library/1,		% :FileSpec
   55            use_foreign_library/2,		% :FileSpec, +Install
   56            prolog_load_context/2,
   57            stream_position_data/3,
   58            current_predicate/2,
   59            '$defined_predicate'/1,
   60            predicate_property/2,
   61            '$predicate_property'/2,
   62            (dynamic)/2,                        % :Predicates, +Options
   63            clause_property/2,
   64            current_module/1,                   % ?Module
   65            module_property/2,                  % ?Module, ?Property
   66            module/1,                           % +Module
   67            current_trie/1,                     % ?Trie
   68            trie_property/2,                    % ?Trie, ?Property
   69            working_directory/2,                % -OldDir, +NewDir
   70            shell/1,                            % +Command
   71            on_signal/3,
   72            current_signal/3,
   73            open_shared_object/2,
   74            open_shared_object/3,
   75            format/1,
   76            garbage_collect/0,
   77            set_prolog_stack/2,
   78            prolog_stack_property/2,
   79            absolute_file_name/2,
   80            tmp_file_stream/3,                  % +Enc, -File, -Stream
   81            call_with_depth_limit/3,            % :Goal, +Limit, -Result
   82            call_with_inference_limit/3,        % :Goal, +Limit, -Result
   83            numbervars/3,                       % +Term, +Start, -End
   84            term_string/3,                      % ?Term, ?String, +Options
   85            nb_setval/2,                        % +Var, +Value
   86            thread_create/2,                    % :Goal, -Id
   87            thread_join/1,                      % +Id
   88            set_prolog_gc_thread/1,		% +Status
   89
   90            '$wrap_predicate'/5                 % :Head, +Name, -Closure, -Wrapped, +Body
   91          ]).   92
   93:- meta_predicate
   94    dynamic(:, +),
   95    use_foreign_library(:),
   96    use_foreign_library(:, +).   97
   98
   99                /********************************
  100                *           DEBUGGER            *
  101                *********************************/
 map_bits(:Pred, +Modify, +OldBits, -NewBits)
  105:- meta_predicate
  106    map_bits(2, +, +, -).  107
  108map_bits(_, Var, _, _) :-
  109    var(Var),
  110    !,
  111    '$instantiation_error'(Var).
  112map_bits(_, [], Bits, Bits) :- !.
  113map_bits(Pred, [H|T], Old, New) :-
  114    map_bits(Pred, H, Old, New0),
  115    map_bits(Pred, T, New0, New).
  116map_bits(Pred, +Name, Old, New) :-     % set a bit
  117    !,
  118    bit(Pred, Name, Bits),
  119    !,
  120    New is Old \/ Bits.
  121map_bits(Pred, -Name, Old, New) :-     % clear a bit
  122    !,
  123    bit(Pred, Name, Bits),
  124    !,
  125    New is Old /\ (\Bits).
  126map_bits(Pred, ?(Name), Old, Old) :-   % ask a bit
  127    !,
  128    bit(Pred, Name, Bits),
  129    Old /\ Bits > 0.
  130map_bits(_, Term, _, _) :-
  131    '$type_error'('+|-|?(Flag)', Term).
  132
  133bit(Pred, Name, Bits) :-
  134    call(Pred, Name, Bits),
  135    !.
  136bit(_:Pred, Name, _) :-
  137    '$domain_error'(Pred, Name).
  138
  139:- public port_name/2.                  % used by library(test_cover)
  140
  141port_name(      call, 2'000000001).
  142port_name(      exit, 2'000000010).
  143port_name(      fail, 2'000000100).
  144port_name(      redo, 2'000001000).
  145port_name(     unify, 2'000010000).
  146port_name(     break, 2'000100000).
  147port_name(  cut_call, 2'001000000).
  148port_name(  cut_exit, 2'010000000).
  149port_name( exception, 2'100000000).
  150port_name(       cut, 2'011000000).
  151port_name(       all, 2'000111111).
  152port_name(      full, 2'000101111).
  153port_name(      half, 2'000101101).     % '
  154
  155leash(Ports) :-
  156    '$leash'(Old, Old),
  157    map_bits(port_name, Ports, Old, New),
  158    '$leash'(_, New).
  159
  160visible(Ports) :-
  161    '$visible'(Old, Old),
  162    map_bits(port_name, Ports, Old, New),
  163    '$visible'(_, New).
  164
  165style_name(atom,            0x0001) :-
  166    print_message(warning, decl_no_effect(style_check(atom))).
  167style_name(singleton,       0x0042).            % semantic and syntactic
  168style_name(discontiguous,   0x0008).
  169style_name(charset,         0x0020).
  170style_name(no_effect,       0x0080).
  171style_name(var_branches,    0x0100).
 style_check(+Spec) is nondet
  175style_check(Var) :-
  176    var(Var),
  177    !,
  178    '$instantiation_error'(Var).
  179style_check(?(Style)) :-
  180    !,
  181    (   var(Style)
  182    ->  enum_style_check(Style)
  183    ;   enum_style_check(Style)
  184    ->  true
  185    ).
  186style_check(Spec) :-
  187    '$style_check'(Old, Old),
  188    map_bits(style_name, Spec, Old, New),
  189    '$style_check'(_, New).
  190
  191enum_style_check(Style) :-
  192    '$style_check'(Bits, Bits),
  193    style_name(Style, Bit),
  194    Bit /\ Bits =\= 0.
 prolog:debug_control_hook(+Action)
Allow user-hooks in the Prolog debugger interaction. See the calls below for the provided hooks. We use a single predicate with action argument to avoid an uncontrolled poliferation of hooks.
  203:- multifile
  204    prolog:debug_control_hook/1.    % +Action
  205
  206:- meta_predicate
  207    spy(:),
  208    nospy(:).
 spy(:Spec) is det
 nospy(:Spec) is det
 nospyall is det
Set/clear spy-points. A successfully set or cleared spy-point is reported using print_message/2, level informational, with one of the following terms, where Spec is of the form M:Head.
See also
- spy/1 and nospy/1 call the hook debug_control_hook/1 to allow for alternative specifications of the thing to debug.
  225spy(_:X) :-
  226    var(X),
  227    throw(error(instantiation_error, _)).
  228spy(_:[]) :- !.
  229spy(M:[H|T]) :-
  230    !,
  231    spy(M:H),
  232    spy(M:T).
  233spy(Spec) :-
  234    notrace(prolog:debug_control_hook(spy(Spec))),
  235    !.
  236spy(Spec) :-
  237    '$find_predicate'(Spec, Preds),
  238    '$member'(PI, Preds),
  239        pi_to_head(PI, Head),
  240        '$define_predicate'(Head),
  241        '$spy'(Head),
  242    fail.
  243spy(_).
  244
  245nospy(_:X) :-
  246    var(X),
  247    throw(error(instantiation_error, _)).
  248nospy(_:[]) :- !.
  249nospy(M:[H|T]) :-
  250    !,
  251    nospy(M:H),
  252    nospy(M:T).
  253nospy(Spec) :-
  254    notrace(prolog:debug_control_hook(nospy(Spec))),
  255    !.
  256nospy(Spec) :-
  257    '$find_predicate'(Spec, Preds),
  258    '$member'(PI, Preds),
  259         pi_to_head(PI, Head),
  260        '$nospy'(Head),
  261    fail.
  262nospy(_).
  263
  264nospyall :-
  265    notrace(prolog:debug_control_hook(nospyall)),
  266    fail.
  267nospyall :-
  268    spy_point(Head),
  269        '$nospy'(Head),
  270    fail.
  271nospyall.
  272
  273pi_to_head(M:PI, M:Head) :-
  274    !,
  275    pi_to_head(PI, Head).
  276pi_to_head(Name/Arity, Head) :-
  277    functor(Head, Name, Arity).
 debugging is det
Report current status of the debugger.
  283debugging :-
  284    notrace(prolog:debug_control_hook(debugging)),
  285    !.
  286debugging :-
  287    current_prolog_flag(debug, true),
  288    !,
  289    print_message(informational, debugging(on)),
  290    findall(H, spy_point(H), SpyPoints),
  291    print_message(informational, spying(SpyPoints)).
  292debugging :-
  293    print_message(informational, debugging(off)).
  294
  295spy_point(Module:Head) :-
  296    current_predicate(_, Module:Head),
  297    '$get_predicate_attribute'(Module:Head, spy, 1),
  298    \+ predicate_property(Module:Head, imported_from(_)).
 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.
  305flag(Name, Old, New) :-
  306    Old == New,
  307    !,
  308    get_flag(Name, Old).
  309flag(Name, Old, New) :-
  310    with_mutex('$flag', update_flag(Name, Old, New)).
  311
  312update_flag(Name, Old, New) :-
  313    get_flag(Name, Old),
  314    (   atom(New)
  315    ->  set_flag(Name, New)
  316    ;   Value is New,
  317        set_flag(Name, Value)
  318    ).
  319
  320
  321                /********************************
  322                *             ATOMS             *
  323                *********************************/
  324
  325dwim_match(A1, A2) :-
  326    dwim_match(A1, A2, _).
  327
  328atom_prefix(Atom, Prefix) :-
  329    sub_atom(Atom, 0, _, _, Prefix).
  330
  331
  332                /********************************
  333                *             SOURCE            *
  334                *********************************/
 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 = 0.0 is used by PlDoc and other code that needs to create a file record without being interested in the time.

  347source_file(File) :-
  348    (   current_prolog_flag(access_level, user)
  349    ->  Level = user
  350    ;   true
  351    ),
  352    (   ground(File)
  353    ->  (   '$time_source_file'(File, Time, Level)
  354        ;   absolute_file_name(File, Abs),
  355            '$time_source_file'(Abs, Time, Level)
  356        ), !
  357    ;   '$time_source_file'(File, Time, Level)
  358    ),
  359    Time > 0.0.
 source_file(+Head, -File) is semidet
source_file(?Head, ?File) is nondet
True when Head is a predicate owned by File.
  366:- meta_predicate source_file(:, ?).  367
  368source_file(M:Head, File) :-
  369    nonvar(M), nonvar(Head),
  370    !,
  371    (   '$c_current_predicate'(_, M:Head),
  372        predicate_property(M:Head, multifile)
  373    ->  multi_source_files(M:Head, Files),
  374        '$member'(File, Files)
  375    ;   '$source_file'(M:Head, File)
  376    ).
  377source_file(M:Head, File) :-
  378    (   nonvar(File)
  379    ->  true
  380    ;   source_file(File)
  381    ),
  382    '$source_file_predicates'(File, Predicates),
  383    '$member'(M:Head, Predicates).
  384
  385:- thread_local found_src_file/1.  386
  387multi_source_files(Head, Files) :-
  388    call_cleanup(
  389        findall(File, multi_source_file(Head, File), Files),
  390        retractall(found_src_file(_))).
  391
  392multi_source_file(Head, File) :-
  393    nth_clause(Head, _, Clause),
  394    clause_property(Clause, source(File)),
  395    \+ found_src_file(File),
  396    asserta(found_src_file(File)).
 source_file_property(?File, ?Property) is nondet
True if Property is a property of the loaded source-file File.
  403source_file_property(File, P) :-
  404    nonvar(File),
  405    !,
  406    canonical_source_file(File, Path),
  407    property_source_file(P, Path).
  408source_file_property(File, P) :-
  409    property_source_file(P, File).
  410
  411property_source_file(modified(Time), File) :-
  412    '$time_source_file'(File, Time, user).
  413property_source_file(source(Source), File) :-
  414    (   '$source_file_property'(File, from_state, true)
  415    ->  Source = state
  416    ;   '$source_file_property'(File, resource, true)
  417    ->  Source = resource
  418    ;   Source = file
  419    ).
  420property_source_file(module(M), File) :-
  421    (   nonvar(M)
  422    ->  '$current_module'(M, File)
  423    ;   nonvar(File)
  424    ->  '$current_module'(ML, File),
  425        (   atom(ML)
  426        ->  M = ML
  427        ;   '$member'(M, ML)
  428        )
  429    ;   '$current_module'(M, File)
  430    ).
  431property_source_file(load_context(Module, Location, Options), File) :-
  432    '$time_source_file'(File, _, user),
  433    clause(system:'$load_context_module'(File, Module, Options), true, Ref),
  434    (   clause_property(Ref, file(FromFile)),
  435        clause_property(Ref, line_count(FromLine))
  436    ->  Location = FromFile:FromLine
  437    ;   Location = user
  438    ).
  439property_source_file(includes(Master, Stamp), File) :-
  440    system:'$included'(File, _Line, Master, Stamp).
  441property_source_file(included_in(Master, Line), File) :-
  442    system:'$included'(Master, Line, File, _).
  443property_source_file(derived_from(DerivedFrom, Stamp), File) :-
  444    system:'$derived_source'(File, DerivedFrom, Stamp).
  445property_source_file(reloading, File) :-
  446    source_file(File),
  447    '$source_file_property'(File, reloading, true).
  448property_source_file(load_count(Count), File) :-
  449    source_file(File),
  450    '$source_file_property'(File, load_count, Count).
  451property_source_file(number_of_clauses(Count), File) :-
  452    source_file(File),
  453    '$source_file_property'(File, number_of_clauses, Count).
 canonical_source_file(+Spec, -File) is semidet
File is the canonical representation of the source-file Spec.
  460canonical_source_file(Spec, File) :-
  461    atom(Spec),
  462    '$time_source_file'(Spec, _, _),
  463    !,
  464    File = Spec.
  465canonical_source_file(Spec, File) :-
  466    system:'$included'(_Master, _Line, Spec, _),
  467    !,
  468    File = Spec.
  469canonical_source_file(Spec, File) :-
  470    absolute_file_name(Spec,
  471                           [ file_type(prolog),
  472                             access(read),
  473                             file_errors(fail)
  474                           ],
  475                           File),
  476    source_file(File).
 exists_source(+Source) is semidet
 exists_source(+Source, -Path) is semidet
True if Source (a term valid for load_files/2) exists. Fails without error if this is not the case. The predicate is intended to be used with :- if, as in the example below. See also source_exports/2.
:- if(exists_source(library(error))).
:- use_module_library(error).
:- endif.
  493exists_source(Source) :-
  494    exists_source(Source, _Path).
  495
  496exists_source(Source, Path) :-
  497    absolute_file_name(Source, Path,
  498                       [ file_type(prolog),
  499                         access(read),
  500                         file_errors(fail)
  501                       ]).
 prolog_load_context(+Key, -Value)
Provides context information for term_expansion and directives. Note that only the line-number info is valid for the '$stream_position'. Largely Quintus compatible.
  510prolog_load_context(module, Module) :-
  511    '$current_source_module'(Module).
  512prolog_load_context(file, File) :-
  513    input_file(File).
  514prolog_load_context(source, F) :-       % SICStus compatibility
  515    input_file(F0),
  516    '$input_context'(Context),
  517    '$top_file'(Context, F0, F).
  518prolog_load_context(stream, S) :-
  519    (   system:'$load_input'(_, S0)
  520    ->  S = S0
  521    ).
  522prolog_load_context(directory, D) :-
  523    input_file(F),
  524    file_directory_name(F, D).
  525prolog_load_context(dialect, D) :-
  526    current_prolog_flag(emulated_dialect, D).
  527prolog_load_context(term_position, TermPos) :-
  528    source_location(_, L),
  529    (   nb_current('$term_position', Pos),
  530        compound(Pos),              % actually set
  531        stream_position_data(line_count, Pos, L)
  532    ->  TermPos = Pos
  533    ;   TermPos = '$stream_position'(0,L,0,0)
  534    ).
  535prolog_load_context(script, Bool) :-
  536    (   '$toplevel':loaded_init_file(script, Path),
  537        input_file(File),
  538        same_file(File, Path)
  539    ->  Bool = true
  540    ;   Bool = false
  541    ).
  542prolog_load_context(variable_names, Bindings) :-
  543    nb_current('$variable_names', Bindings).
  544prolog_load_context(term, Term) :-
  545    nb_current('$term', Term).
  546prolog_load_context(reloading, true) :-
  547    prolog_load_context(source, F),
  548    '$source_file_property'(F, reloading, true).
  549
  550input_file(File) :-
  551    (   system:'$load_input'(_, Stream)
  552    ->  stream_property(Stream, file_name(File))
  553    ),
  554    !.
  555input_file(File) :-
  556    source_location(File, _).
 unload_file(+File) is det
Remove all traces of loading file.
  563:- dynamic system:'$resolved_source_path'/2.  564
  565unload_file(File) :-
  566    (   canonical_source_file(File, Path)
  567    ->  '$unload_file'(Path),
  568        retractall(system:'$resolved_source_path'(_, Path))
  569    ;   true
  570    ).
  571
  572		 /*******************************
  573		 *      FOREIGN LIBRARIES	*
  574		 *******************************/
 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.

  593use_foreign_library(FileSpec) :-
  594    ensure_shlib,
  595    initialization(shlib:load_foreign_library(FileSpec), now).
  596
  597use_foreign_library(FileSpec, Entry) :-
  598    ensure_shlib,
  599    initialization(shlib:load_foreign_library(FileSpec, Entry), now).
  600
  601ensure_shlib :-
  602    '$get_predicate_attribute'(shlib:load_foreign_library(_), defined, 1),
  603    '$get_predicate_attribute'(shlib:load_foreign_library(_,_), defined, 1),
  604    !.
  605ensure_shlib :-
  606    use_module(library(shlib), []).
  607
  608
  609                 /*******************************
  610                 *            STREAMS           *
  611                 *******************************/
 stream_position_data(?Field, +Pos, ?Date)
Extract values from stream position objects. '$stream_position' is of the format '$stream_position'(Byte, Char, Line, LinePos)
  618stream_position_data(Prop, Term, Value) :-
  619    nonvar(Prop),
  620    !,
  621    (   stream_position_field(Prop, Pos)
  622    ->  arg(Pos, Term, Value)
  623    ;   throw(error(domain_error(stream_position_data, Prop)))
  624    ).
  625stream_position_data(Prop, Term, Value) :-
  626    stream_position_field(Prop, Pos),
  627    arg(Pos, Term, Value).
  628
  629stream_position_field(char_count,    1).
  630stream_position_field(line_count,    2).
  631stream_position_field(line_position, 3).
  632stream_position_field(byte_count,    4).
  633
  634
  635                 /*******************************
  636                 *            CONTROL           *
  637                 *******************************/
 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.
  645:- meta_predicate
  646    call_with_depth_limit(0, +, -).  647
  648call_with_depth_limit(G, Limit, Result) :-
  649    '$depth_limit'(Limit, OLimit, OReached),
  650    (   catch(G, E, '$depth_limit_except'(OLimit, OReached, E)),
  651        '$depth_limit_true'(Limit, OLimit, OReached, Result, Det),
  652        ( Det == ! -> ! ; true )
  653    ;   '$depth_limit_false'(OLimit, OReached, Result)
  654    ).
 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.

  668:- meta_predicate
  669    call_with_inference_limit(0, +, -).  670
  671call_with_inference_limit(G, Limit, Result) :-
  672    '$inference_limit'(Limit, OLimit),
  673    (   catch(G, Except,
  674              system:'$inference_limit_except'(OLimit, Except, Result0)),
  675        system:'$inference_limit_true'(Limit, OLimit, Result0),
  676        ( Result0 == ! -> ! ; true ),
  677        Result = Result0
  678    ;   system:'$inference_limit_false'(OLimit)
  679    ).
  680
  681
  682                /********************************
  683                *           DATA BASE           *
  684                *********************************/
  685
  686/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  687The predicate current_predicate/2 is   a  difficult subject since  the
  688introduction  of defaulting     modules   and   dynamic     libraries.
  689current_predicate/2 is normally  called with instantiated arguments to
  690verify some  predicate can   be called without trapping   an undefined
  691predicate.  In this case we must  perform the search algorithm used by
  692the prolog system itself.
  693
  694If the pattern is not fully specified, we only generate the predicates
  695actually available in this  module.   This seems the best for listing,
  696etc.
  697- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  698
  699
  700:- meta_predicate
  701    current_predicate(?, :),
  702    '$defined_predicate'(:).  703
  704current_predicate(Name, Module:Head) :-
  705    (var(Module) ; var(Head)),
  706    !,
  707    generate_current_predicate(Name, Module, Head).
  708current_predicate(Name, Term) :-
  709    '$c_current_predicate'(Name, Term),
  710    '$defined_predicate'(Term),
  711    !.
  712current_predicate(Name, Module:Head) :-
  713    default_module(Module, DefModule),
  714    '$c_current_predicate'(Name, DefModule:Head),
  715    '$defined_predicate'(DefModule:Head),
  716    !.
  717current_predicate(Name, Module:Head) :-
  718    '$autoload':autoload_in(Module, general),
  719    \+ current_prolog_flag(Module:unknown, fail),
  720    (   compound(Head)
  721    ->  compound_name_arity(Head, Name, Arity)
  722    ;   Name = Head, Arity = 0
  723    ),
  724    '$find_library'(Module, Name, Arity, _LoadModule, _Library),
  725    !.
  726
  727generate_current_predicate(Name, Module, Head) :-
  728    current_module(Module),
  729    QHead = Module:Head,
  730    '$c_current_predicate'(Name, QHead),
  731    '$get_predicate_attribute'(QHead, defined, 1).
  732
  733'$defined_predicate'(Head) :-
  734    '$get_predicate_attribute'(Head, defined, 1),
  735    !.
 predicate_property(?Predicate, ?Property) is nondet
True when Property is a property of Predicate.
  741:- meta_predicate
  742    predicate_property(:, ?).  743
  744:- multifile
  745    '$predicate_property'/2.  746
  747:- '$iso'(predicate_property/2).  748
  749predicate_property(Pred, Property) :-           % Mode ?,+
  750    nonvar(Property),
  751    !,
  752    property_predicate(Property, Pred).
  753predicate_property(Pred, Property) :-           % Mode +,-
  754    define_or_generate(Pred),
  755    '$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.
  763property_predicate(undefined, Pred) :-
  764    !,
  765    Pred = Module:Head,
  766    current_module(Module),
  767    '$c_current_predicate'(_, Pred),
  768    \+ '$defined_predicate'(Pred),          % Speed up a bit
  769    \+ current_predicate(_, Pred),
  770    goal_name_arity(Head, Name, Arity),
  771    \+ system_undefined(Module:Name/Arity).
  772property_predicate(visible, Pred) :-
  773    !,
  774    visible_predicate(Pred).
  775property_predicate(autoload(File), Head) :-
  776    !,
  777    \+ current_prolog_flag(autoload, false),
  778    '$autoload':autoloadable(Head, File).
  779property_predicate(implementation_module(IM), M:Head) :-
  780    !,
  781    atom(M),
  782    (   default_module(M, DM),
  783        '$get_predicate_attribute'(DM:Head, defined, 1)
  784    ->  (   '$get_predicate_attribute'(DM:Head, imported, ImportM)
  785        ->  IM = ImportM
  786        ;   IM = M
  787        )
  788    ;   \+ current_prolog_flag(M:unknown, fail),
  789        goal_name_arity(Head, Name, Arity),
  790        '$find_library'(_, Name, Arity, LoadModule, _File)
  791    ->  IM = LoadModule
  792    ;   M = IM
  793    ).
  794property_predicate(iso, _:Head) :-
  795    callable(Head),
  796    !,
  797    goal_name_arity(Head, Name, Arity),
  798    current_predicate(system:Name/Arity),
  799    '$predicate_property'(iso, system:Head).
  800property_predicate(built_in, Module:Head) :-
  801    callable(Head),
  802    !,
  803    goal_name_arity(Head, Name, Arity),
  804    current_predicate(Module:Name/Arity),
  805    '$predicate_property'(built_in, Module:Head).
  806property_predicate(Property, Pred) :-
  807    define_or_generate(Pred),
  808    '$predicate_property'(Property, Pred).
  809
  810goal_name_arity(Head, Name, Arity) :-
  811    compound(Head),
  812    !,
  813    compound_name_arity(Head, Name, Arity).
  814goal_name_arity(Head, Head, 0).
 define_or_generate(+Head) is semidet
define_or_generate(-Head) is nondet
If the predicate is known, try to resolve it. Otherwise generate the known predicate, but do not try to (auto)load the predicate.
  823define_or_generate(M:Head) :-
  824    callable(Head),
  825    atom(M),
  826    '$get_predicate_attribute'(M:Head, defined, 1),
  827    !.
  828define_or_generate(M:Head) :-
  829    callable(Head),
  830    nonvar(M), M \== system,
  831    !,
  832    '$define_predicate'(M:Head).
  833define_or_generate(Pred) :-
  834    current_predicate(_, Pred),
  835    '$define_predicate'(Pred).
  836
  837
  838'$predicate_property'(interpreted, Pred) :-
  839    '$get_predicate_attribute'(Pred, foreign, 0).
  840'$predicate_property'(visible, Pred) :-
  841    '$get_predicate_attribute'(Pred, defined, 1).
  842'$predicate_property'(built_in, Pred) :-
  843    '$get_predicate_attribute'(Pred, system, 1).
  844'$predicate_property'(exported, Pred) :-
  845    '$get_predicate_attribute'(Pred, exported, 1).
  846'$predicate_property'(public, Pred) :-
  847    '$get_predicate_attribute'(Pred, public, 1).
  848'$predicate_property'(non_terminal, Pred) :-
  849    '$get_predicate_attribute'(Pred, non_terminal, 1).
  850'$predicate_property'(foreign, Pred) :-
  851    '$get_predicate_attribute'(Pred, foreign, 1).
  852'$predicate_property'((dynamic), Pred) :-
  853    '$get_predicate_attribute'(Pred, (dynamic), 1).
  854'$predicate_property'((static), Pred) :-
  855    '$get_predicate_attribute'(Pred, (dynamic), 0).
  856'$predicate_property'((volatile), Pred) :-
  857    '$get_predicate_attribute'(Pred, (volatile), 1).
  858'$predicate_property'((thread_local), Pred) :-
  859    '$get_predicate_attribute'(Pred, (thread_local), 1).
  860'$predicate_property'((multifile), Pred) :-
  861    '$get_predicate_attribute'(Pred, (multifile), 1).
  862'$predicate_property'(imported_from(Module), Pred) :-
  863    '$get_predicate_attribute'(Pred, imported, Module).
  864'$predicate_property'(transparent, Pred) :-
  865    '$get_predicate_attribute'(Pred, transparent, 1).
  866'$predicate_property'(meta_predicate(Pattern), Pred) :-
  867    '$get_predicate_attribute'(Pred, meta_predicate, Pattern).
  868'$predicate_property'(file(File), Pred) :-
  869    '$get_predicate_attribute'(Pred, file, File).
  870'$predicate_property'(line_count(LineNumber), Pred) :-
  871    '$get_predicate_attribute'(Pred, line_count, LineNumber).
  872'$predicate_property'(notrace, Pred) :-
  873    '$get_predicate_attribute'(Pred, trace, 0).
  874'$predicate_property'(nodebug, Pred) :-
  875    '$get_predicate_attribute'(Pred, hide_childs, 1).
  876'$predicate_property'(spying, Pred) :-
  877    '$get_predicate_attribute'(Pred, spy, 1).
  878'$predicate_property'(number_of_clauses(N), Pred) :-
  879    '$get_predicate_attribute'(Pred, number_of_clauses, N).
  880'$predicate_property'(number_of_rules(N), Pred) :-
  881    '$get_predicate_attribute'(Pred, number_of_rules, N).
  882'$predicate_property'(last_modified_generation(Gen), Pred) :-
  883    '$get_predicate_attribute'(Pred, last_modified_generation, Gen).
  884'$predicate_property'(indexed(Indices), Pred) :-
  885    '$get_predicate_attribute'(Pred, indexed, Indices).
  886'$predicate_property'(noprofile, Pred) :-
  887    '$get_predicate_attribute'(Pred, noprofile, 1).
  888'$predicate_property'(iso, Pred) :-
  889    '$get_predicate_attribute'(Pred, iso, 1).
  890'$predicate_property'(quasi_quotation_syntax, Pred) :-
  891    '$get_predicate_attribute'(Pred, quasi_quotation_syntax, 1).
  892'$predicate_property'(defined, Pred) :-
  893    '$get_predicate_attribute'(Pred, defined, 1).
  894'$predicate_property'(tabled, Pred) :-
  895    '$get_predicate_attribute'(Pred, tabled, 1).
  896'$predicate_property'(tabled(Flag), Pred) :-
  897    '$get_predicate_attribute'(Pred, tabled, 1),
  898    table_flag(Flag, Pred).
  899'$predicate_property'(incremental, Pred) :-
  900    '$get_predicate_attribute'(Pred, incremental, 1).
  901'$predicate_property'(abstract(N), Pred) :-
  902    '$get_predicate_attribute'(Pred, abstract, N).
  903'$predicate_property'(size(Bytes), Pred) :-
  904    '$get_predicate_attribute'(Pred, size, Bytes).
  905
  906system_undefined(user:prolog_trace_interception/4).
  907system_undefined(user:prolog_exception_hook/4).
  908system_undefined(system:'$c_call_prolog'/0).
  909system_undefined(system:window_title/2).
  910
  911table_flag(variant, Pred) :-
  912    '$tbl_implementation'(Pred, M:Head),
  913    M:'$tabled'(Head, variant).
  914table_flag(subsumptive, Pred) :-
  915    '$tbl_implementation'(Pred, M:Head),
  916    M:'$tabled'(Head, subsumptive).
  917table_flag(shared, Pred) :-
  918    '$get_predicate_attribute'(Pred, tshared, 1).
  919table_flag(incremental, Pred) :-
  920    '$get_predicate_attribute'(Pred, incremental, 1).
  921table_flag(monotonic, Pred) :-
  922    '$get_predicate_attribute'(Pred, monotonic, 1).
  923table_flag(subgoal_abstract(N), Pred) :-
  924    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  925table_flag(answer_abstract(N), Pred) :-
  926    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  927table_flag(subgoal_abstract(N), Pred) :-
  928    '$get_predicate_attribute'(Pred, max_answers, N).
 visible_predicate(:Head) is nondet
True when Head can be called without raising an existence error. This implies it is defined, can be inherited from a default module or can be autoloaded.
  937visible_predicate(Pred) :-
  938    Pred = M:Head,
  939    current_module(M),
  940    (   callable(Head)
  941    ->  (   '$get_predicate_attribute'(Pred, defined, 1)
  942        ->  true
  943        ;   \+ current_prolog_flag(M:unknown, fail),
  944            functor(Head, Name, Arity),
  945            '$find_library'(M, Name, Arity, _LoadModule, _Library)
  946        )
  947    ;   setof(PI, visible_in_module(M, PI), PIs),
  948        '$member'(Name/Arity, PIs),
  949        functor(Head, Name, Arity)
  950    ).
  951
  952visible_in_module(M, Name/Arity) :-
  953    default_module(M, DefM),
  954    DefHead = DefM:Head,
  955    '$c_current_predicate'(_, DefHead),
  956    '$get_predicate_attribute'(DefHead, defined, 1),
  957    \+ hidden_system_predicate(Head),
  958    functor(Head, Name, Arity).
  959visible_in_module(_, Name/Arity) :-
  960    '$in_library'(Name, Arity, _).
  961
  962hidden_system_predicate(Head) :-
  963    functor(Head, Name, _),
  964    atom(Name),                     % Avoid [].
  965    sub_atom(Name, 0, _, _, $),
  966    \+ current_prolog_flag(access_level, system).
 clause_property(+ClauseRef, ?Property) is nondet
Provide information on individual clauses. Defined properties are:
line_count(-Line)
Line from which the clause is loaded.
file(-File)
File from which the clause is loaded.
source(-File)
File that `owns' the clause: reloading this file wipes the clause.
fact
Clause has body true.
erased
Clause was erased.
predicate(:PI)
Predicate indicator of the predicate this clause belongs to. Can be used to find the predicate of erased clauses.
module(-M)
Module context in which the clause was compiled.
  991clause_property(Clause, Property) :-
  992    '$clause_property'(Property, Clause).
  993
  994'$clause_property'(line_count(LineNumber), Clause) :-
  995    '$get_clause_attribute'(Clause, line_count, LineNumber).
  996'$clause_property'(file(File), Clause) :-
  997    '$get_clause_attribute'(Clause, file, File).
  998'$clause_property'(source(File), Clause) :-
  999    '$get_clause_attribute'(Clause, owner, File).
 1000'$clause_property'(size(Bytes), Clause) :-
 1001    '$get_clause_attribute'(Clause, size, Bytes).
 1002'$clause_property'(fact, Clause) :-
 1003    '$get_clause_attribute'(Clause, fact, true).
 1004'$clause_property'(erased, Clause) :-
 1005    '$get_clause_attribute'(Clause, erased, true).
 1006'$clause_property'(predicate(PI), Clause) :-
 1007    '$get_clause_attribute'(Clause, predicate_indicator, PI).
 1008'$clause_property'(module(M), Clause) :-
 1009    '$get_clause_attribute'(Clause, module, M).
 dynamic(:Predicates, +Options) is det
Define a predicate as dynamic with optionally additional properties. Defined options are:
 1023dynamic(M:Predicates, Options) :-
 1024    '$must_be'(list, Predicates),
 1025    options_properties(Options, Props),
 1026    set_pprops(Predicates, M, [dynamic|Props]).
 1027
 1028set_pprops([], _, _).
 1029set_pprops([H|T], M, Props) :-
 1030    set_pprops1(Props, M:H),
 1031    strip_module(M:H, M2, P),
 1032    '$pi_head'(M2:P, Pred),
 1033    '$set_table_wrappers'(Pred),
 1034    set_pprops(T, M, Props).
 1035
 1036set_pprops1([], _).
 1037set_pprops1([H|T], P) :-
 1038    (   atom(H)
 1039    ->  '$set_predicate_attribute'(P, H, true)
 1040    ;   H =.. [Name,Value]
 1041    ->  '$set_predicate_attribute'(P, Name, Value)
 1042    ),
 1043    set_pprops1(T, P).
 1044
 1045options_properties(Options, Props) :-
 1046    G = opt_prop(_,_,_,_),
 1047    findall(G, G, Spec),
 1048    options_properties(Spec, Options, Props).
 1049
 1050options_properties([], _, []).
 1051options_properties([opt_prop(Name, Type, SetValue, Prop)|T],
 1052                   Options, [Prop|PT]) :-
 1053    Opt =.. [Name,V],
 1054    '$option'(Opt, Options),
 1055    '$must_be'(Type, V),
 1056    V = SetValue,
 1057    !,
 1058    options_properties(T, Options, PT).
 1059options_properties([_|T], Options, PT) :-
 1060    options_properties(T, Options, PT).
 1061
 1062opt_prop(incremental,   boolean,               Bool,  incremental(Bool)).
 1063opt_prop(abstract,      between(0,0),          0,     abstract).
 1064opt_prop(multifile,     boolean,               true,  multifile).
 1065opt_prop(discontiguous, boolean,               true,  discontiguous).
 1066opt_prop(volatile,      boolean,               true,  volatile).
 1067opt_prop(thread,        oneof(atom, [local,shared],[local,shared]),
 1068                                               local, thread_local).
 1069
 1070                /********************************
 1071                *            MODULES            *
 1072                *********************************/
 current_module(?Module) is nondet
True if Module is a currently defined module.
 1078current_module(Module) :-
 1079    '$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.
 1095module_property(Module, Property) :-
 1096    nonvar(Module), nonvar(Property),
 1097    !,
 1098    property_module(Property, Module).
 1099module_property(Module, Property) :-    % -, file(File)
 1100    nonvar(Property), Property = file(File),
 1101    !,
 1102    (   nonvar(File)
 1103    ->  '$current_module'(Modules, File),
 1104        (   atom(Modules)
 1105        ->  Module = Modules
 1106        ;   '$member'(Module, Modules)
 1107        )
 1108    ;   '$current_module'(Module, File),
 1109        File \== []
 1110    ).
 1111module_property(Module, Property) :-
 1112    current_module(Module),
 1113    property_module(Property, Module).
 1114
 1115property_module(Property, Module) :-
 1116    module_property(Property),
 1117    (   Property = exported_operators(List)
 1118    ->  '$exported_ops'(Module, List, [])
 1119    ;   '$module_property'(Module, Property)
 1120    ).
 1121
 1122module_property(class(_)).
 1123module_property(file(_)).
 1124module_property(line_count(_)).
 1125module_property(exports(_)).
 1126module_property(exported_operators(_)).
 1127module_property(size(_)).
 1128module_property(program_size(_)).
 1129module_property(program_space(_)).
 1130module_property(last_modified_generation(_)).
 module(+Module) is det
Set the module that is associated to the toplevel to Module.
 1136module(Module) :-
 1137    atom(Module),
 1138    current_module(Module),
 1139    !,
 1140    '$set_typein_module'(Module).
 1141module(Module) :-
 1142    '$set_typein_module'(Module),
 1143    print_message(warning, no_current_module(Module)).
 working_directory(-Old, +New)
True when Old is the current working directory and the working directory has been updated to New.
 1150working_directory(Old, New) :-
 1151    '$cwd'(Old),
 1152    (   Old == New
 1153    ->  true
 1154    ;   '$chdir'(New)
 1155    ).
 1156
 1157
 1158                 /*******************************
 1159                 *            TRIES             *
 1160                 *******************************/
 current_trie(?Trie) is nondet
True if Trie is the handle of an existing trie.
 1166current_trie(Trie) :-
 1167    current_blob(Trie, trie),
 1168    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
 1204trie_property(Trie, Property) :-
 1205    current_trie(Trie),
 1206    trie_property(Property),
 1207    '$trie_property'(Trie, Property).
 1208
 1209trie_property(node_count(_)).
 1210trie_property(value_count(_)).
 1211trie_property(size(_)).
 1212trie_property(hashed(_)).
 1213trie_property(compiled_size(_)).
 1214                                                % below only when -DO_TRIE_STATS
 1215trie_property(lookup_count(_)).                 % is enabled in pl-trie.h
 1216trie_property(gen_call_count(_)).
 1217trie_property(invalidated(_)).                  % IDG stats
 1218trie_property(reevaluated(_)).
 1219trie_property(deadlock(_)).                     % Shared tabling stats
 1220trie_property(wait(_)).
 1221trie_property(idg_affected_count(_)).
 1222trie_property(idg_dependent_count(_)).
 1223trie_property(idg_size(_)).
 1224
 1225
 1226                /********************************
 1227                *      SYSTEM INTERACTION       *
 1228                *********************************/
 1229
 1230shell(Command) :-
 1231    shell(Command, 0).
 1232
 1233
 1234                 /*******************************
 1235                 *            SIGNALS           *
 1236                 *******************************/
 1237
 1238:- meta_predicate
 1239    on_signal(+, :, :),
 1240    current_signal(?, ?, :).
 on_signal(+Signal, -OldHandler, :NewHandler) is det
 1244on_signal(Signal, Old, New) :-
 1245    atom(Signal),
 1246    !,
 1247    '$on_signal'(_Num, Signal, Old, New).
 1248on_signal(Signal, Old, New) :-
 1249    integer(Signal),
 1250    !,
 1251    '$on_signal'(Signal, _Name, Old, New).
 1252on_signal(Signal, _Old, _New) :-
 1253    '$type_error'(signal_name, Signal).
 current_signal(?Name, ?SignalNumber, :Handler) is nondet
 1257current_signal(Name, Id, Handler) :-
 1258    between(1, 32, Id),
 1259    '$on_signal'(Id, Name, Handler, Handler).
 1260
 1261:- multifile
 1262    prolog:called_by/2. 1263
 1264prolog:called_by(on_signal(_,_,New), [New+1]) :-
 1265    (   new == throw
 1266    ;   new == default
 1267    ), !, fail.
 1268
 1269
 1270                 /*******************************
 1271                 *            DLOPEN            *
 1272                 *******************************/
 open_shared_object(+File, -Handle) is det
 open_shared_object(+File, -Handle, +Flags) is det
Open a shared object or DLL file. Flags is a list of flags. The following flags are recognised. Note however that these flags may have no affect on the target platform.
 1286open_shared_object(File, Handle) :-
 1287    open_shared_object(File, Handle, []). % use pl-load.c defaults
 1288
 1289open_shared_object(File, Handle, Flags) :-
 1290    (   is_list(Flags)
 1291    ->  true
 1292    ;   throw(error(type_error(list, Flags), _))
 1293    ),
 1294    map_dlflags(Flags, Mask),
 1295    '$open_shared_object'(File, Handle, Mask).
 1296
 1297dlopen_flag(now,        2'01).          % see pl-load.c for these constants
 1298dlopen_flag(global,     2'10).          % Solaris only
 1299
 1300map_dlflags([], 0).
 1301map_dlflags([F|T], M) :-
 1302    map_dlflags(T, M0),
 1303    (   dlopen_flag(F, I)
 1304    ->  true
 1305    ;   throw(error(domain_error(dlopen_flag, F), _))
 1306    ),
 1307    M is M0 \/ I.
 1308
 1309
 1310                 /*******************************
 1311                 *             I/O              *
 1312                 *******************************/
 1313
 1314format(Fmt) :-
 1315    format(Fmt, []).
 1316
 1317                 /*******************************
 1318                 *            FILES             *
 1319                 *******************************/
 absolute_file_name(+Term, -AbsoluteFile)
 1323absolute_file_name(Name, Abs) :-
 1324    atomic(Name),
 1325    !,
 1326    '$absolute_file_name'(Name, Abs).
 1327absolute_file_name(Term, Abs) :-
 1328    '$chk_file'(Term, [''], [access(read)], true, File),
 1329    !,
 1330    '$absolute_file_name'(File, Abs).
 1331absolute_file_name(Term, Abs) :-
 1332    '$chk_file'(Term, [''], [], true, File),
 1333    !,
 1334    '$absolute_file_name'(File, Abs).
 tmp_file_stream(-File, -Stream, +Options) is det
tmp_file_stream(+Encoding, -File, -Stream) is det
Create a temporary file and open it atomically. The second mode is for compatibility reasons.
 1342tmp_file_stream(Enc, File, Stream) :-
 1343    atom(Enc), var(File), var(Stream),
 1344    !,
 1345    '$tmp_file_stream'('', Enc, File, Stream).
 1346tmp_file_stream(File, Stream, Options) :-
 1347    current_prolog_flag(encoding, DefEnc),
 1348    '$option'(encoding(Enc), Options, DefEnc),
 1349    '$option'(extension(Ext), Options, ''),
 1350    '$tmp_file_stream'(Ext, Enc, File, Stream),
 1351    set_stream(Stream, file_name(File)).
 1352
 1353
 1354                /********************************
 1355                *        MEMORY MANAGEMENT      *
 1356                *********************************/
 garbage_collect is det
Invoke the garbage collector. The argument of the underlying '$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.
 1365garbage_collect :-
 1366    '$garbage_collect'(0).
 set_prolog_stack(+Name, +Option) is det
Set a parameter for one of the Prolog stacks.
 1372set_prolog_stack(Stack, Option) :-
 1373    Option =.. [Name,Value0],
 1374    Value is Value0,
 1375    '$set_prolog_stack'(Stack, Name, _Old, Value).
 prolog_stack_property(?Stack, ?Property) is nondet
Examine stack properties.
 1381prolog_stack_property(Stack, Property) :-
 1382    stack_property(P),
 1383    stack_name(Stack),
 1384    Property =.. [P,Value],
 1385    '$set_prolog_stack'(Stack, P, Value, Value).
 1386
 1387stack_name(local).
 1388stack_name(global).
 1389stack_name(trail).
 1390
 1391stack_property(limit).
 1392stack_property(spare).
 1393stack_property(min_free).
 1394stack_property(low).
 1395stack_property(factor).
 1396
 1397
 1398                 /*******************************
 1399                 *             TERM             *
 1400                 *******************************/
 1401
 1402:- '$iso'((numbervars/3)).
 numbervars(+Term, +StartIndex, -EndIndex) is det
Number all unbound variables in Term using '$VAR'(N), where the first N is StartIndex and EndIndex is unified to the index that will be given to the next variable.
 1410numbervars(Term, From, To) :-
 1411    numbervars(Term, From, To, []).
 1412
 1413
 1414                 /*******************************
 1415                 *            STRING            *
 1416                 *******************************/
 term_string(?Term, ?String, +Options)
Parse/write a term from/to a string using Options.
 1422term_string(Term, String, Options) :-
 1423    nonvar(String),
 1424    !,
 1425    read_term_from_atom(String, Term, Options).
 1426term_string(Term, String, Options) :-
 1427    (   '$option'(quoted(_), Options)
 1428    ->  Options1 = Options
 1429    ;   '$merge_options'(_{quoted:true}, Options, Options1)
 1430    ),
 1431    format(string(String), '~W', [Term, Options1]).
 1432
 1433
 1434                 /*******************************
 1435                 *             GVAR             *
 1436                 *******************************/
 nb_setval(+Name, +Value) is det
Bind the non-backtrackable variable Name with a copy of Value
 1442nb_setval(Name, Value) :-
 1443    duplicate_term(Value, Copy),
 1444    nb_linkval(Name, Copy).
 1445
 1446
 1447		 /*******************************
 1448		 *            THREADS		*
 1449		 *******************************/
 1450
 1451:- meta_predicate
 1452    thread_create(0, -).
 thread_create(:Goal, -Id)
Shorthand for thread_create(Goal, Id, []).
 1458thread_create(Goal, Id) :-
 1459    thread_create(Goal, Id, []).
 thread_join(+Id)
Join a thread and raise an error of the thread did not succeed.
Errors
- thread_error(Status), where Status is the result of thread_join/2.
 1468thread_join(Id) :-
 1469    thread_join(Id, Status),
 1470    (   Status == true
 1471    ->  true
 1472    ;   throw(error(thread_error(Id, Status), _))
 1473    ).
 set_prolog_gc_thread(+Status)
Control the GC thread. Status is one of
false
Disable the separate GC thread, running atom and clause garbage collection in the triggering thread.
true
Enable the separate GC thread. All implicit atom and clause garbage collection is executed by the thread gc.
stop
Stop the gc thread if it is running. The thread is recreated on the next implicit atom or clause garbage collection. Used by fork/1 to avoid forking a multi-threaded application.
 1490set_prolog_gc_thread(Status) :-
 1491    var(Status),
 1492    !,
 1493    '$instantiation_error'(Status).
 1494set_prolog_gc_thread(false) :-
 1495    !,
 1496    set_prolog_flag(gc_thread, false),
 1497    (   current_prolog_flag(threads, true)
 1498    ->  (   '$gc_stop'
 1499        ->  thread_join(gc)
 1500        ;   true
 1501        )
 1502    ;   true
 1503    ).
 1504set_prolog_gc_thread(true) :-
 1505    !,
 1506    set_prolog_flag(gc_thread, true).
 1507set_prolog_gc_thread(stop) :-
 1508    !,
 1509    (   current_prolog_flag(threads, true)
 1510    ->  (   '$gc_stop'
 1511        ->  thread_join(gc)
 1512        ;   true
 1513        )
 1514    ;   true
 1515    ).
 1516set_prolog_gc_thread(Status) :-
 1517    '$domain_error'(gc_thread, Status).
 $wrap_predicate(:Head, +Name, -Closure, -Wrapped, +Body) is det
Would be nicer to have this from library(prolog_wrap), but we need it for tabling, so it must be a system predicate.
 1524:- meta_predicate
 1525    '$wrap_predicate'(:, +, -, -, +). 1526
 1527'$wrap_predicate'(M:Head, WName, Closure, call(Wrapped), Body) :-
 1528    callable_name_arguments(Head, PName, Args),
 1529    callable_name_arity(Head, PName, Arity),
 1530    (   is_most_general_term(Head)
 1531    ->  true
 1532    ;   '$domain_error'(most_general_term, Head)
 1533    ),
 1534    atomic_list_concat(['$wrap$', PName], WrapName),
 1535    volatile(M:WrapName/Arity),
 1536    module_transparent(M:WrapName/Arity),
 1537    WHead =.. [WrapName|Args],
 1538    '$c_wrap_predicate'(M:Head, WName, Closure, Wrapped, M:(WHead :- Body)).
 1539
 1540callable_name_arguments(Head, PName, Args) :-
 1541    atom(Head),
 1542    !,
 1543    PName = Head,
 1544    Args = [].
 1545callable_name_arguments(Head, PName, Args) :-
 1546    compound_name_arguments(Head, PName, Args).
 1547
 1548callable_name_arity(Head, PName, Arity) :-
 1549    atom(Head),
 1550    !,
 1551    PName = Head,
 1552    Arity = 0.
 1553callable_name_arity(Head, PName, Arity) :-
 1554    compound_name_arity(Head, PName, Arity)