syspred.pl

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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)  1985-2022, 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            nb_setval/2,                        % +Var, +Value
   81            thread_create/2,                    % :Goal, -Id
   82            thread_join/1,                      % +Id
   83            sig_block/1,                        % :Pattern
   84            sig_unblock/1,                      % :Pattern
   85            transaction/1,                      % :Goal
   86            transaction/2,                      % :Goal, +Options
   87            transaction/3,                      % :Goal, :Constraint, +Mutex
   88            snapshot/1,                         % :Goal
   89            undo/1,                             % :Goal
   90            set_prolog_gc_thread/1,		% +Status
   91
   92            '$wrap_predicate'/5                 % :Head, +Name, -Closure, -Wrapped, +Body
   93          ]).   94
   95:- meta_predicate
   96    dynamic(:, +),
   97    transaction(0),
   98    transaction(0,0,+),
   99    snapshot(0),
  100    rule(:, -),
  101    rule(:, -, ?),
  102    sig_block(:),
  103    sig_unblock(:).  104
  105
  106                /********************************
  107                *           DEBUGGER            *
  108                *********************************/

map_bits(:Pred, +Modify, +OldBits, -NewBits)

  112:- meta_predicate
  113    map_bits(2, +, +, -).  114
  115map_bits(_, Var, _, _) :-
  116    var(Var),
  117    !,
  118    '$instantiation_error'(Var).
  119map_bits(_, [], Bits, Bits) :- !.
  120map_bits(Pred, [H|T], Old, New) :-
  121    map_bits(Pred, H, Old, New0),
  122    map_bits(Pred, T, New0, New).
  123map_bits(Pred, +Name, Old, New) :-     % set a bit
  124    !,
  125    bit(Pred, Name, Bits),
  126    !,
  127    New is Old \/ Bits.
  128map_bits(Pred, -Name, Old, New) :-     % clear a bit
  129    !,
  130    bit(Pred, Name, Bits),
  131    !,
  132    New is Old /\ (\Bits).
  133map_bits(Pred, ?(Name), Old, Old) :-   % ask a bit
  134    !,
  135    bit(Pred, Name, Bits),
  136    Old /\ Bits > 0.
  137map_bits(_, Term, _, _) :-
  138    '$type_error'('+|-|?(Flag)', Term).
  139
  140bit(Pred, Name, Bits) :-
  141    call(Pred, Name, Bits),
  142    !.
  143bit(_:Pred, Name, _) :-
  144    '$domain_error'(Pred, Name).
  145
  146:- public port_name/2.                  % used by library(test_cover)
  147
  148port_name(      call, 2'000000001).
  149port_name(      exit, 2'000000010).
  150port_name(      fail, 2'000000100).
  151port_name(      redo, 2'000001000).
  152port_name(     unify, 2'000010000).
  153port_name(     break, 2'000100000).
  154port_name(  cut_call, 2'001000000).
  155port_name(  cut_exit, 2'010000000).
  156port_name( exception, 2'100000000).
  157port_name(       cut, 2'011000000).
  158port_name(       all, 2'000111111).
  159port_name(      full, 2'000101111).
  160port_name(      half, 2'000101101).     % '
  161
  162leash(Ports) :-
  163    '$leash'(Old, Old),
  164    map_bits(port_name, Ports, Old, New),
  165    '$leash'(_, New).
  166
  167visible(Ports) :-
  168    '$visible'(Old, Old),
  169    map_bits(port_name, Ports, Old, New),
  170    '$visible'(_, New).
  171
  172style_name(atom,            0x0001) :-
  173    print_message(warning, decl_no_effect(style_check(atom))).
  174style_name(singleton,       0x0042).            % semantic and syntactic
  175style_name(discontiguous,   0x0008).
  176style_name(charset,         0x0020).
  177style_name(no_effect,       0x0080).
  178style_name(var_branches,    0x0100).

style_check(+Spec) is nondet

  182style_check(Var) :-
  183    var(Var),
  184    !,
  185    '$instantiation_error'(Var).
  186style_check(?(Style)) :-
  187    !,
  188    (   var(Style)
  189    ->  enum_style_check(Style)
  190    ;   enum_style_check(Style)
  191    ->  true
  192    ).
  193style_check(Spec) :-
  194    '$style_check'(Old, Old),
  195    map_bits(style_name, Spec, Old, New),
  196    '$style_check'(_, New).
  197
  198enum_style_check(Style) :-
  199    '$style_check'(Bits, Bits),
  200    style_name(Style, Bit),
  201    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.

  209flag(Name, Old, New) :-
  210    Old == New,
  211    !,
  212    get_flag(Name, Old).
  213flag(Name, Old, New) :-
  214    with_mutex('$flag', update_flag(Name, Old, New)).
  215
  216update_flag(Name, Old, New) :-
  217    get_flag(Name, Old),
  218    (   atom(New)
  219    ->  set_flag(Name, New)
  220    ;   Value is New,
  221        set_flag(Name, Value)
  222    ).
  223
  224
  225                /********************************
  226                *             ATOMS             *
  227                *********************************/
  228
  229dwim_match(A1, A2) :-
  230    dwim_match(A1, A2, _).
  231
  232atom_prefix(Atom, Prefix) :-
  233    sub_atom(Atom, 0, _, _, Prefix).
  234
  235
  236                /********************************
  237                *             SOURCE            *
  238                *********************************/

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.

  251source_file(File) :-
  252    (   current_prolog_flag(access_level, user)
  253    ->  Level = user
  254    ;   true
  255    ),
  256    (   ground(File)
  257    ->  (   '$time_source_file'(File, Time, Level)
  258        ;   absolute_file_name(File, Abs),
  259            '$time_source_file'(Abs, Time, Level)
  260        ), !
  261    ;   '$time_source_file'(File, Time, Level)
  262    ),
  263    float(Time).

source_file(+Head, -File) is semidet
source_file(?Head, ?File) is nondet: True when Head is a predicate owned by File.

  270:- meta_predicate source_file(:, ?).  271
  272source_file(M:Head, File) :-
  273    nonvar(M), nonvar(Head),
  274    !,
  275    (   '$c_current_predicate'(_, M:Head),
  276        predicate_property(M:Head, multifile)
  277    ->  multi_source_file(M:Head, File)
  278    ;   '$source_file'(M:Head, File)
  279    ).
  280source_file(M:Head, File) :-
  281    (   nonvar(File)
  282    ->  true
  283    ;   source_file(File)
  284    ),
  285    '$source_file_predicates'(File, Predicates),
  286    '$member'(M:Head, Predicates).
  287
  288multi_source_file(Head, File) :-
  289    State = state([]),
  290    nth_clause(Head, _, Clause),
  291    clause_property(Clause, source(File)),
  292    arg(1, State, Found),
  293    (   memberchk(File, Found)
  294    ->  fail
  295    ;   nb_linkarg(1, State, [File|Found])
  296    ).

source_file_property(?File, ?Property) is nondet: True if Property is a property of the loaded source-file File.

  303source_file_property(File, P) :-
  304    nonvar(File),
  305    !,
  306    canonical_source_file(File, Path),
  307    property_source_file(P, Path).
  308source_file_property(File, P) :-
  309    property_source_file(P, File).
  310
  311property_source_file(modified(Time), File) :-
  312    '$time_source_file'(File, Time, user).
  313property_source_file(source(Source), File) :-
  314    (   '$source_file_property'(File, from_state, true)
  315    ->  Source = state
  316    ;   '$source_file_property'(File, resource, true)
  317    ->  Source = resource
  318    ;   Source = file
  319    ).
  320property_source_file(module(M), File) :-
  321    (   nonvar(M)
  322    ->  '$current_module'(M, File)
  323    ;   nonvar(File)
  324    ->  '$current_module'(ML, File),
  325        (   atom(ML)
  326        ->  M = ML
  327        ;   '$member'(M, ML)
  328        )
  329    ;   '$current_module'(M, File)
  330    ).
  331property_source_file(load_context(Module, Location, Options), File) :-
  332    '$time_source_file'(File, _, user),
  333    clause(system:'$load_context_module'(File, Module, Options), true, Ref),
  334    (   clause_property(Ref, file(FromFile)),
  335        clause_property(Ref, line_count(FromLine))
  336    ->  Location = FromFile:FromLine
  337    ;   Location = user
  338    ).
  339property_source_file(includes(Master, Stamp), File) :-
  340    system:'$included'(File, _Line, Master, Stamp).
  341property_source_file(included_in(Master, Line), File) :-
  342    system:'$included'(Master, Line, File, _).
  343property_source_file(derived_from(DerivedFrom, Stamp), File) :-
  344    system:'$derived_source'(File, DerivedFrom, Stamp).
  345property_source_file(reloading, File) :-
  346    source_file(File),
  347    '$source_file_property'(File, reloading, true).
  348property_source_file(load_count(Count), File) :-
  349    source_file(File),
  350    '$source_file_property'(File, load_count, Count).
  351property_source_file(number_of_clauses(Count), File) :-
  352    source_file(File),
  353    '$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.

  360canonical_source_file(Spec, File) :-
  361    atom(Spec),
  362    '$time_source_file'(Spec, _, _),
  363    !,
  364    File = Spec.
  365canonical_source_file(Spec, File) :-
  366    system:'$included'(_Master, _Line, Spec, _),
  367    !,
  368    File = Spec.
  369canonical_source_file(Spec, File) :-
  370    absolute_file_name(Spec, File,
  371                       [ file_type(prolog),
  372                         access(read),
  373                         file_errors(fail)
  374                       ]),
  375    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.

  392exists_source(Source) :-
  393    exists_source(Source, _Path).
  394
  395exists_source(Source, Path) :-
  396    absolute_file_name(Source, Path,
  397                       [ file_type(prolog),
  398                         access(read),
  399                         file_errors(fail)
  400                       ]).

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.

  409prolog_load_context(module, Module) :-
  410    '$current_source_module'(Module).
  411prolog_load_context(file, File) :-
  412    input_file(File).
  413prolog_load_context(source, F) :-       % SICStus compatibility
  414    input_file(F0),
  415    '$input_context'(Context),
  416    '$top_file'(Context, F0, F).
  417prolog_load_context(stream, S) :-
  418    (   system:'$load_input'(_, S0)
  419    ->  S = S0
  420    ).
  421prolog_load_context(directory, D) :-
  422    input_file(F),
  423    file_directory_name(F, D).
  424prolog_load_context(dialect, D) :-
  425    current_prolog_flag(emulated_dialect, D).
  426prolog_load_context(term_position, TermPos) :-
  427    source_location(_, L),
  428    (   nb_current('$term_position', Pos),
  429        compound(Pos),              % actually set
  430        stream_position_data(line_count, Pos, L)
  431    ->  TermPos = Pos
  432    ;   TermPos = '$stream_position'(0,L,0,0)
  433    ).
  434prolog_load_context(script, Bool) :-
  435    (   '$toplevel':loaded_init_file(script, Path),
  436        input_file(File),
  437        same_file(File, Path)
  438    ->  Bool = true
  439    ;   Bool = false
  440    ).
  441prolog_load_context(variable_names, Bindings) :-
  442    (   nb_current('$variable_names', Bindings0)
  443    ->  Bindings = Bindings0
  444    ;   Bindings = []
  445    ).
  446prolog_load_context(term, Term) :-
  447    nb_current('$term', Term).
  448prolog_load_context(reloading, true) :-
  449    prolog_load_context(source, F),
  450    '$source_file_property'(F, reloading, true).
  451
  452input_file(File) :-
  453    (   system:'$load_input'(_, Stream)
  454    ->  stream_property(Stream, file_name(File))
  455    ),
  456    !.
  457input_file(File) :-
  458    source_location(File, _).

unload_file(+File) is det: Remove all traces of loading file.

  465:- dynamic system:'$resolved_source_path'/2.  466
  467unload_file(File) :-
  468    (   canonical_source_file(File, Path)
  469    ->  '$unload_file'(Path),
  470        retractall(system:'$resolved_source_path'(_, Path))
  471    ;   true
  472    ).
  473
  474:- if(current_prolog_flag(open_shared_object, true)).  475
  476		 /*******************************
  477		 *      FOREIGN LIBRARIES	*
  478		 *******************************/

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.

  497:- meta_predicate
  498    use_foreign_library(:),
  499    use_foreign_library(:, +).  500:- public
  501    use_foreign_library_noi/1.  502
  503use_foreign_library(FileSpec) :-
  504    ensure_shlib,
  505    initialization(use_foreign_library_noi(FileSpec), now).
  506
  507% noi -> no initialize; used by '$autoload':exports/3.
  508use_foreign_library_noi(FileSpec) :-
  509    ensure_shlib,
  510    shlib:load_foreign_library(FileSpec).
  511
  512use_foreign_library(FileSpec, Options) :-
  513    ensure_shlib,
  514    initialization(shlib:load_foreign_library(FileSpec, Options), now).
  515
  516ensure_shlib :-
  517    '$get_predicate_attribute'(shlib:load_foreign_library(_), defined, 1),
  518    '$get_predicate_attribute'(shlib:load_foreign_library(_,_), defined, 1),
  519    !.
  520ensure_shlib :-
  521    use_module(library(shlib), []).
  522
  523:- export(use_foreign_library/1).  524:- export(use_foreign_library/2).  525
  526:- elif(current_predicate('$activate_static_extension'/1)).  527
  528% Version when using shared objects is disabled and extensions are added
  529% as static libraries.
  530
  531:- meta_predicate
  532    use_foreign_library(:).  533:- public
  534    use_foreign_library_noi/1.  535:- dynamic
  536    loading/1,
  537    foreign_predicate/2.  538
  539use_foreign_library(FileSpec) :-
  540    initialization(use_foreign_library_noi(FileSpec), now).
  541
  542use_foreign_library_noi(Module:foreign(Extension)) :-
  543    setup_call_cleanup(
  544        asserta(loading(foreign(Extension)), Ref),
  545        @('$activate_static_extension'(Extension), Module),
  546        erase(Ref)).
  547
  548:- export(use_foreign_library/1).  549
  550system:'$foreign_registered'(M, H) :-
  551    (   loading(Lib)
  552    ->  true
  553    ;   Lib = '<spontaneous>'
  554    ),
  555    assert(foreign_predicate(Lib, M:H)).

current_foreign_library(?File, -Public): Query currently loaded shared libraries.

  561current_foreign_library(File, Public) :-
  562    setof(Pred, foreign_predicate(File, Pred), Public).
  563
  564:- export(current_foreign_library/2).  565
  566:- endif. /* open_shared_object support */
  567
  568                 /*******************************
  569                 *            STREAMS           *
  570                 *******************************/

stream_position_data(?Field, +Pos, ?Date): Extract values from stream position objects. '$stream_position' is of the format '$stream_position'(Byte, Char, Line, LinePos)

  577stream_position_data(Prop, Term, Value) :-
  578    nonvar(Prop),
  579    !,
  580    (   stream_position_field(Prop, Pos)
  581    ->  arg(Pos, Term, Value)
  582    ;   throw(error(domain_error(stream_position_data, Prop)))
  583    ).
  584stream_position_data(Prop, Term, Value) :-
  585    stream_position_field(Prop, Pos),
  586    arg(Pos, Term, Value).
  587
  588stream_position_field(char_count,    1).
  589stream_position_field(line_count,    2).
  590stream_position_field(line_position, 3).
  591stream_position_field(byte_count,    4).
  592
  593
  594                 /*******************************
  595                 *            CONTROL           *
  596                 *******************************/

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.

  604:- meta_predicate
  605    call_with_depth_limit(0, +, -).  606
  607call_with_depth_limit(G, Limit, Result) :-
  608    '$depth_limit'(Limit, OLimit, OReached),
  609    (   catch(G, E, '$depth_limit_except'(OLimit, OReached, E)),
  610        '$depth_limit_true'(Limit, OLimit, OReached, Result, Det),
  611        ( Det == ! -> ! ; true )
  612    ;   '$depth_limit_false'(OLimit, OReached, Result)
  613    ).

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.

  626:- meta_predicate
  627    call_with_inference_limit(0, +, -).  628
  629call_with_inference_limit(G, Limit, Result) :-
  630    '$inference_limit'(Limit, OLimit),
  631    (   catch(G, Except,
  632              system:'$inference_limit_except'(OLimit, Except, Result0)),
  633        (   Result0 == inference_limit_exceeded
  634        ->  !
  635        ;   system:'$inference_limit_true'(Limit, OLimit, Result0),
  636            ( Result0 == ! -> ! ; true )
  637        ),
  638        Result = Result0
  639    ;   system:'$inference_limit_false'(OLimit)
  640    ).
  641
  642
  643                /********************************
  644                *           DATA BASE           *
  645                *********************************/
  646
  647/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  648The predicate current_predicate/2 is   a  difficult subject since  the
  649introduction  of defaulting     modules   and   dynamic     libraries.
  650current_predicate/2 is normally  called with instantiated arguments to
  651verify some  predicate can   be called without trapping   an undefined
  652predicate.  In this case we must  perform the search algorithm used by
  653the prolog system itself.
  654
  655If the pattern is not fully specified, we only generate the predicates
  656actually available in this  module.   This seems the best for listing,
  657etc.
  658- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  659
  660
  661:- meta_predicate
  662    current_predicate(?, :),
  663    '$defined_predicate'(:).  664
  665current_predicate(Name, Module:Head) :-
  666    (var(Module) ; var(Head)),
  667    !,
  668    generate_current_predicate(Name, Module, Head).
  669current_predicate(Name, Term) :-
  670    '$c_current_predicate'(Name, Term),
  671    '$defined_predicate'(Term),
  672    !.
  673current_predicate(Name, Module:Head) :-
  674    default_module(Module, DefModule),
  675    '$c_current_predicate'(Name, DefModule:Head),
  676    '$defined_predicate'(DefModule:Head),
  677    !.
  678current_predicate(Name, Module:Head) :-
  679    '$autoload':autoload_in(Module, general),
  680    \+ current_prolog_flag(Module:unknown, fail),
  681    (   compound(Head)
  682    ->  compound_name_arity(Head, Name, Arity)
  683    ;   Name = Head, Arity = 0
  684    ),
  685    '$find_library'(Module, Name, Arity, _LoadModule, _Library),
  686    !.
  687
  688generate_current_predicate(Name, Module, Head) :-
  689    current_module(Module),
  690    QHead = Module:Head,
  691    '$c_current_predicate'(Name, QHead),
  692    '$get_predicate_attribute'(QHead, defined, 1).
  693
  694'$defined_predicate'(Head) :-
  695    '$get_predicate_attribute'(Head, defined, 1),
  696    !.

predicate_property(?Predicate, ?Property) is nondet: True when Property is a property of Predicate.

  702:- meta_predicate
  703    predicate_property(:, ?).  704
  705:- multifile
  706    '$predicate_property'/2.  707
  708:- '$iso'(predicate_property/2).  709
  710predicate_property(Pred, Property) :-           % Mode ?,+
  711    nonvar(Property),
  712    !,
  713    property_predicate(Property, Pred).
  714predicate_property(Pred, Property) :-           % Mode +,-
  715    define_or_generate(Pred),
  716    '$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.

  724property_predicate(undefined, Pred) :-
  725    !,
  726    Pred = Module:Head,
  727    current_module(Module),
  728    '$c_current_predicate'(_, Pred),
  729    \+ '$defined_predicate'(Pred),          % Speed up a bit
  730    \+ current_predicate(_, Pred),
  731    goal_name_arity(Head, Name, Arity),
  732    \+ system_undefined(Module:Name/Arity).
  733property_predicate(visible, Pred) :-
  734    !,
  735    visible_predicate(Pred).
  736property_predicate(autoload(File), Head) :-
  737    !,
  738    \+ current_prolog_flag(autoload, false),
  739    '$autoload':autoloadable(Head, File).
  740property_predicate(implementation_module(IM), M:Head) :-
  741    !,
  742    atom(M),
  743    (   default_module(M, DM),
  744        '$get_predicate_attribute'(DM:Head, defined, 1)
  745    ->  (   '$get_predicate_attribute'(DM:Head, imported, ImportM)
  746        ->  IM = ImportM
  747        ;   IM = M
  748        )
  749    ;   \+ current_prolog_flag(M:unknown, fail),
  750        goal_name_arity(Head, Name, Arity),
  751        '$find_library'(_, Name, Arity, LoadModule, _File)
  752    ->  IM = LoadModule
  753    ;   M = IM
  754    ).
  755property_predicate(iso, _:Head) :-
  756    callable(Head),
  757    !,
  758    goal_name_arity(Head, Name, Arity),
  759    current_predicate(system:Name/Arity),
  760    '$predicate_property'(iso, system:Head).
  761property_predicate(built_in, Module:Head) :-
  762    callable(Head),
  763    !,
  764    goal_name_arity(Head, Name, Arity),
  765    current_predicate(Module:Name/Arity),
  766    '$predicate_property'(built_in, Module:Head).
  767property_predicate(Property, Pred) :-
  768    define_or_generate(Pred),
  769    '$predicate_property'(Property, Pred).
  770
  771goal_name_arity(Head, Name, Arity) :-
  772    compound(Head),
  773    !,
  774    compound_name_arity(Head, Name, Arity).
  775goal_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.

  784define_or_generate(M:Head) :-
  785    callable(Head),
  786    atom(M),
  787    '$get_predicate_attribute'(M:Head, defined, 1),
  788    !.
  789define_or_generate(M:Head) :-
  790    callable(Head),
  791    nonvar(M), M \== system,
  792    !,
  793    '$define_predicate'(M:Head).
  794define_or_generate(Pred) :-
  795    current_predicate(_, Pred),
  796    '$define_predicate'(Pred).
  797
  798
  799'$predicate_property'(interpreted, Pred) :-
  800    '$get_predicate_attribute'(Pred, foreign, 0).
  801'$predicate_property'(visible, Pred) :-
  802    '$get_predicate_attribute'(Pred, defined, 1).
  803'$predicate_property'(built_in, Pred) :-
  804    '$get_predicate_attribute'(Pred, system, 1).
  805'$predicate_property'(exported, Pred) :-
  806    '$get_predicate_attribute'(Pred, exported, 1).
  807'$predicate_property'(public, Pred) :-
  808    '$get_predicate_attribute'(Pred, public, 1).
  809'$predicate_property'(non_terminal, Pred) :-
  810    '$get_predicate_attribute'(Pred, non_terminal, 1).
  811'$predicate_property'(foreign, Pred) :-
  812    '$get_predicate_attribute'(Pred, foreign, 1).
  813'$predicate_property'((dynamic), Pred) :-
  814    '$get_predicate_attribute'(Pred, (dynamic), 1).
  815'$predicate_property'((static), Pred) :-
  816    '$get_predicate_attribute'(Pred, (dynamic), 0).
  817'$predicate_property'((volatile), Pred) :-
  818    '$get_predicate_attribute'(Pred, (volatile), 1).
  819'$predicate_property'((thread_local), Pred) :-
  820    '$get_predicate_attribute'(Pred, (thread_local), 1).
  821'$predicate_property'((multifile), Pred) :-
  822    '$get_predicate_attribute'(Pred, (multifile), 1).
  823'$predicate_property'((discontiguous), Pred) :-
  824    '$get_predicate_attribute'(Pred, (discontiguous), 1).
  825'$predicate_property'(imported_from(Module), Pred) :-
  826    '$get_predicate_attribute'(Pred, imported, Module).
  827'$predicate_property'(transparent, Pred) :-
  828    '$get_predicate_attribute'(Pred, transparent, 1).
  829'$predicate_property'(meta_predicate(Pattern), Pred) :-
  830    '$get_predicate_attribute'(Pred, meta_predicate, Pattern).
  831'$predicate_property'(file(File), Pred) :-
  832    '$get_predicate_attribute'(Pred, file, File).
  833'$predicate_property'(line_count(LineNumber), Pred) :-
  834    '$get_predicate_attribute'(Pred, line_count, LineNumber).
  835'$predicate_property'(notrace, Pred) :-
  836    '$get_predicate_attribute'(Pred, trace, 0).
  837'$predicate_property'(nodebug, Pred) :-
  838    '$get_predicate_attribute'(Pred, hide_childs, 1).
  839'$predicate_property'(spying, Pred) :-
  840    '$get_predicate_attribute'(Pred, spy, 1).
  841'$predicate_property'(number_of_clauses(N), Pred) :-
  842    '$get_predicate_attribute'(Pred, number_of_clauses, N).
  843'$predicate_property'(number_of_rules(N), Pred) :-
  844    '$get_predicate_attribute'(Pred, number_of_rules, N).
  845'$predicate_property'(last_modified_generation(Gen), Pred) :-
  846    '$get_predicate_attribute'(Pred, last_modified_generation, Gen).
  847'$predicate_property'(indexed(Indices), Pred) :-
  848    '$get_predicate_attribute'(Pred, indexed, Indices).
  849'$predicate_property'(noprofile, Pred) :-
  850    '$get_predicate_attribute'(Pred, noprofile, 1).
  851'$predicate_property'(ssu, Pred) :-
  852    '$get_predicate_attribute'(Pred, ssu, 1).
  853'$predicate_property'(iso, Pred) :-
  854    '$get_predicate_attribute'(Pred, iso, 1).
  855'$predicate_property'(det, Pred) :-
  856    '$get_predicate_attribute'(Pred, det, 1).
  857'$predicate_property'(sig_atomic, Pred) :-
  858    '$get_predicate_attribute'(Pred, sig_atomic, 1).
  859'$predicate_property'(quasi_quotation_syntax, Pred) :-
  860    '$get_predicate_attribute'(Pred, quasi_quotation_syntax, 1).
  861'$predicate_property'(defined, Pred) :-
  862    '$get_predicate_attribute'(Pred, defined, 1).
  863'$predicate_property'(tabled, Pred) :-
  864    '$get_predicate_attribute'(Pred, tabled, 1).
  865'$predicate_property'(tabled(Flag), Pred) :-
  866    '$get_predicate_attribute'(Pred, tabled, 1),
  867    table_flag(Flag, Pred).
  868'$predicate_property'(incremental, Pred) :-
  869    '$get_predicate_attribute'(Pred, incremental, 1).
  870'$predicate_property'(monotonic, Pred) :-
  871    '$get_predicate_attribute'(Pred, monotonic, 1).
  872'$predicate_property'(opaque, Pred) :-
  873    '$get_predicate_attribute'(Pred, opaque, 1).
  874'$predicate_property'(lazy, Pred) :-
  875    '$get_predicate_attribute'(Pred, lazy, 1).
  876'$predicate_property'(abstract(N), Pred) :-
  877    '$get_predicate_attribute'(Pred, abstract, N).
  878'$predicate_property'(size(Bytes), Pred) :-
  879    '$get_predicate_attribute'(Pred, size, Bytes).
  880
  881system_undefined(user:prolog_trace_interception/4).
  882system_undefined(prolog:prolog_exception_hook/5).
  883system_undefined(system:'$c_call_prolog'/0).
  884system_undefined(system:window_title/2).
  885
  886table_flag(variant, Pred) :-
  887    '$tbl_implementation'(Pred, M:Head),
  888    M:'$tabled'(Head, variant).
  889table_flag(subsumptive, Pred) :-
  890    '$tbl_implementation'(Pred, M:Head),
  891    M:'$tabled'(Head, subsumptive).
  892table_flag(shared, Pred) :-
  893    '$get_predicate_attribute'(Pred, tshared, 1).
  894table_flag(incremental, Pred) :-
  895    '$get_predicate_attribute'(Pred, incremental, 1).
  896table_flag(monotonic, Pred) :-
  897    '$get_predicate_attribute'(Pred, monotonic, 1).
  898table_flag(subgoal_abstract(N), Pred) :-
  899    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  900table_flag(answer_abstract(N), Pred) :-
  901    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  902table_flag(subgoal_abstract(N), Pred) :-
  903    '$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.

  912visible_predicate(Pred) :-
  913    Pred = M:Head,
  914    current_module(M),
  915    (   callable(Head)
  916    ->  (   '$get_predicate_attribute'(Pred, defined, 1)
  917        ->  true
  918        ;   \+ current_prolog_flag(M:unknown, fail),
  919            '$head_name_arity'(Head, Name, Arity),
  920            '$find_library'(M, Name, Arity, _LoadModule, _Library)
  921        )
  922    ;   setof(PI, visible_in_module(M, PI), PIs),
  923        '$member'(Name/Arity, PIs),
  924        functor(Head, Name, Arity)
  925    ).
  926
  927visible_in_module(M, Name/Arity) :-
  928    default_module(M, DefM),
  929    DefHead = DefM:Head,
  930    '$c_current_predicate'(_, DefHead),
  931    '$get_predicate_attribute'(DefHead, defined, 1),
  932    \+ hidden_system_predicate(Head),
  933    functor(Head, Name, Arity).
  934visible_in_module(_, Name/Arity) :-
  935    '$in_library'(Name, Arity, _).
  936
  937hidden_system_predicate(Head) :-
  938    functor(Head, Name, _),
  939    atom(Name),                     % Avoid [].
  940    sub_atom(Name, 0, _, _, $),
  941    \+ 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.

  966clause_property(Clause, Property) :-
  967    '$clause_property'(Property, Clause).
  968
  969'$clause_property'(line_count(LineNumber), Clause) :-
  970    '$get_clause_attribute'(Clause, line_count, LineNumber).
  971'$clause_property'(file(File), Clause) :-
  972    '$get_clause_attribute'(Clause, file, File).
  973'$clause_property'(source(File), Clause) :-
  974    '$get_clause_attribute'(Clause, owner, File).
  975'$clause_property'(size(Bytes), Clause) :-
  976    '$get_clause_attribute'(Clause, size, Bytes).
  977'$clause_property'(fact, Clause) :-
  978    '$get_clause_attribute'(Clause, fact, true).
  979'$clause_property'(erased, Clause) :-
  980    '$get_clause_attribute'(Clause, erased, true).
  981'$clause_property'(predicate(PI), Clause) :-
  982    '$get_clause_attribute'(Clause, predicate_indicator, PI).
  983'$clause_property'(module(M), Clause) :-
  984    '$get_clause_attribute'(Clause, module, M).

dynamic(:Predicates, +Options) is det

Define a predicate as dynamic with optionally additional properties. Defined options are:

incremental(+Bool)
abstract(+Level)
multifile(+Bool)
discontiguous(+Bool)
thread(+Mode)
volatile(+Bool)

  998dynamic(M:Predicates, Options) :-
  999    '$must_be'(list, Predicates),
 1000    options_properties(Options, Props),
 1001    set_pprops(Predicates, M, [dynamic|Props]).
 1002
 1003set_pprops([], _, _).
 1004set_pprops([H|T], M, Props) :-
 1005    set_pprops1(Props, M:H),
 1006    strip_module(M:H, M2, P),
 1007    '$pi_head'(M2:P, Pred),
 1008    '$set_table_wrappers'(Pred),
 1009    set_pprops(T, M, Props).
 1010
 1011set_pprops1([], _).
 1012set_pprops1([H|T], P) :-
 1013    (   atom(H)
 1014    ->  '$set_predicate_attribute'(P, H, true)
 1015    ;   H =.. [Name,Value]
 1016    ->  '$set_predicate_attribute'(P, Name, Value)
 1017    ),
 1018    set_pprops1(T, P).
 1019
 1020options_properties(Options, Props) :-
 1021    G = opt_prop(_,_,_,_),
 1022    findall(G, G, Spec),
 1023    options_properties(Spec, Options, Props).
 1024
 1025options_properties([], _, []).
 1026options_properties([opt_prop(Name, Type, SetValue, Prop)|T],
 1027                   Options, [Prop|PT]) :-
 1028    Opt =.. [Name,V],
 1029    '$option'(Opt, Options),
 1030    '$must_be'(Type, V),
 1031    V = SetValue,
 1032    !,
 1033    options_properties(T, Options, PT).
 1034options_properties([_|T], Options, PT) :-
 1035    options_properties(T, Options, PT).
 1036
 1037opt_prop(incremental,   boolean,               Bool,  incremental(Bool)).
 1038opt_prop(abstract,      between(0,0),          0,     abstract).
 1039opt_prop(multifile,     boolean,               true,  multifile).
 1040opt_prop(discontiguous, boolean,               true,  discontiguous).
 1041opt_prop(volatile,      boolean,               true,  volatile).
 1042opt_prop(thread,        oneof(atom, [local,shared],[local,shared]),
 1043                                               local, thread_local).
 1044
 1045                /********************************
 1046                *            MODULES            *
 1047                *********************************/

current_module(?Module) is nondet: True if Module is a currently defined module.

 1053current_module(Module) :-
 1054    '$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.

 1070module_property(Module, Property) :-
 1071    nonvar(Module), nonvar(Property),
 1072    !,
 1073    property_module(Property, Module).
 1074module_property(Module, Property) :-    % -, file(File)
 1075    nonvar(Property), Property = file(File),
 1076    !,
 1077    (   nonvar(File)
 1078    ->  '$current_module'(Modules, File),
 1079        (   atom(Modules)
 1080        ->  Module = Modules
 1081        ;   '$member'(Module, Modules)
 1082        )
 1083    ;   '$current_module'(Module, File),
 1084        File \== []
 1085    ).
 1086module_property(Module, Property) :-
 1087    current_module(Module),
 1088    property_module(Property, Module).
 1089
 1090property_module(Property, Module) :-
 1091    module_property(Property),
 1092    (   Property = exported_operators(List)
 1093    ->  '$exported_ops'(Module, List, [])
 1094    ;   '$module_property'(Module, Property)
 1095    ).
 1096
 1097module_property(class(_)).
 1098module_property(file(_)).
 1099module_property(line_count(_)).
 1100module_property(exports(_)).
 1101module_property(exported_operators(_)).
 1102module_property(size(_)).
 1103module_property(program_size(_)).
 1104module_property(program_space(_)).
 1105module_property(last_modified_generation(_)).

module(+Module) is det: Set the module that is associated to the toplevel to Module.

 1111module(Module) :-
 1112    atom(Module),
 1113    current_module(Module),
 1114    !,
 1115    '$set_typein_module'(Module).
 1116module(Module) :-
 1117    '$set_typein_module'(Module),
 1118    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.

 1125working_directory(Old, New) :-
 1126    '$cwd'(Old),
 1127    (   Old == New
 1128    ->  true
 1129    ;   '$chdir'(New)
 1130    ).
 1131
 1132
 1133                 /*******************************
 1134                 *            TRIES             *
 1135                 *******************************/

current_trie(?Trie) is nondet: True if Trie is the handle of an existing trie.

 1141current_trie(Trie) :-
 1142    current_blob(Trie, trie),
 1143    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

 1179trie_property(Trie, Property) :-
 1180    current_trie(Trie),
 1181    trie_property(Property),
 1182    '$trie_property'(Trie, Property).
 1183
 1184trie_property(node_count(_)).
 1185trie_property(value_count(_)).
 1186trie_property(size(_)).
 1187trie_property(hashed(_)).
 1188trie_property(compiled_size(_)).
 1189                                                % below only when -DO_TRIE_STATS
 1190trie_property(lookup_count(_)).                 % is enabled in pl-trie.h
 1191trie_property(gen_call_count(_)).
 1192trie_property(invalidated(_)).                  % IDG stats
 1193trie_property(reevaluated(_)).
 1194trie_property(deadlock(_)).                     % Shared tabling stats
 1195trie_property(wait(_)).
 1196trie_property(idg_affected_count(_)).
 1197trie_property(idg_dependent_count(_)).
 1198trie_property(idg_size(_)).
 1199
 1200
 1201                /********************************
 1202                *      SYSTEM INTERACTION       *
 1203                *********************************/
 1204
 1205shell(Command) :-
 1206    shell(Command, 0).
 1207
 1208
 1209                 /*******************************
 1210                 *            SIGNALS           *
 1211                 *******************************/
 1212
 1213:- meta_predicate
 1214    on_signal(+, :, :),
 1215    current_signal(?, ?, :).

on_signal(+Signal, -OldHandler, :NewHandler) is det

 1219on_signal(Signal, Old, New) :-
 1220    atom(Signal),
 1221    !,
 1222    '$on_signal'(_Num, Signal, Old, New).
 1223on_signal(Signal, Old, New) :-
 1224    integer(Signal),
 1225    !,
 1226    '$on_signal'(Signal, _Name, Old, New).
 1227on_signal(Signal, _Old, _New) :-
 1228    '$type_error'(signal_name, Signal).

current_signal(?Name, ?SignalNumber, :Handler) is nondet

 1232current_signal(Name, Id, Handler) :-
 1233    between(1, 32, Id),
 1234    '$on_signal'(Id, Name, Handler, Handler).
 1235
 1236:- multifile
 1237    prolog:called_by/2. 1238
 1239prolog:called_by(on_signal(_,_,New), [New+1]) :-
 1240    (   new == throw
 1241    ;   new == default
 1242    ), !, fail.
 1243
 1244
 1245                 /*******************************
 1246                 *             I/O              *
 1247                 *******************************/
 1248
 1249format(Fmt) :-
 1250    format(Fmt, []).
 1251
 1252                 /*******************************
 1253                 *            FILES             *
 1254                 *******************************/

absolute_file_name(+Term, -AbsoluteFile)

 1258absolute_file_name(Name, Abs) :-
 1259    atomic(Name),
 1260    !,
 1261    '$absolute_file_name'(Name, Abs).
 1262absolute_file_name(Term, Abs) :-
 1263    '$chk_file'(Term, [''], [access(read)], true, File),
 1264    !,
 1265    '$absolute_file_name'(File, Abs).
 1266absolute_file_name(Term, Abs) :-
 1267    '$chk_file'(Term, [''], [], true, File),
 1268    !,
 1269    '$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.

 1277tmp_file_stream(Enc, File, Stream) :-
 1278    atom(Enc), var(File), var(Stream),
 1279    !,
 1280    '$tmp_file_stream'('', Enc, File, Stream).
 1281tmp_file_stream(File, Stream, Options) :-
 1282    current_prolog_flag(encoding, DefEnc),
 1283    '$option'(encoding(Enc), Options, DefEnc),
 1284    '$option'(extension(Ext), Options, ''),
 1285    '$tmp_file_stream'(Ext, Enc, File, Stream),
 1286    set_stream(Stream, file_name(File)).
 1287
 1288
 1289                /********************************
 1290                *        MEMORY MANAGEMENT      *
 1291                *********************************/

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.

 1300garbage_collect :-
 1301    '$garbage_collect'(0).

set_prolog_stack(+Name, +Option) is det: Set a parameter for one of the Prolog stacks.

 1307set_prolog_stack(Stack, Option) :-
 1308    Option =.. [Name,Value0],
 1309    Value is Value0,
 1310    '$set_prolog_stack'(Stack, Name, _Old, Value).

prolog_stack_property(?Stack, ?Property) is nondet: Examine stack properties.

 1316prolog_stack_property(Stack, Property) :-
 1317    stack_property(P),
 1318    stack_name(Stack),
 1319    Property =.. [P,Value],
 1320    '$set_prolog_stack'(Stack, P, Value, Value).
 1321
 1322stack_name(local).
 1323stack_name(global).
 1324stack_name(trail).
 1325
 1326stack_property(limit).
 1327stack_property(spare).
 1328stack_property(min_free).
 1329stack_property(low).
 1330stack_property(factor).
 1331
 1332
 1333		 /*******************************
 1334		 *            CLAUSE		*
 1335		 *******************************/

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.

 1343rule(Head, Rule) :-
 1344    '$rule'(Head, Rule0),
 1345    conditional_rule(Rule0, Rule1),
 1346    Rule = Rule1.
 1347rule(Head, Rule, Ref) :-
 1348    '$rule'(Head, Rule0, Ref),
 1349    conditional_rule(Rule0, Rule1),
 1350    Rule = Rule1.
 1351
 1352conditional_rule(?=>(Head, (!, Body)), Rule) =>
 1353    Rule = (Head => Body).
 1354conditional_rule(?=>(Head, !), Rule) =>
 1355    Rule = (Head => true).
 1356conditional_rule(?=>(Head, Body0), Rule),
 1357    split_on_cut(Body0, Cond, Body) =>
 1358    Rule = (Head,Cond=>Body).
 1359conditional_rule(Head, Rule) =>
 1360    Rule = Head.
 1361
 1362split_on_cut((Cond0,!,Body0), Cond, Body) =>
 1363    Cond = Cond0,
 1364    Body = Body0.
 1365split_on_cut((!,Body0), Cond, Body) =>
 1366    Cond = true,
 1367    Body = Body0.
 1368split_on_cut((A,B), Cond, Body) =>
 1369    Cond = (A,Cond1),
 1370    split_on_cut(B, Cond1, Body).
 1371split_on_cut(_, _, _) =>
 1372    fail.
 1373
 1374
 1375                 /*******************************
 1376                 *             TERM             *
 1377                 *******************************/
 1378
 1379:- '$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.

 1387numbervars(Term, From, To) :-
 1388    numbervars(Term, From, To, []).
 1389
 1390
 1391                 /*******************************
 1392                 *            STRING            *
 1393                 *******************************/

term_string(?Term, ?String, +Options): Parse/write a term from/to a string using Options.

 1399term_string(Term, String, Options) :-
 1400    nonvar(String),
 1401    !,
 1402    read_term_from_atom(String, Term, Options).
 1403term_string(Term, String, Options) :-
 1404    (   '$option'(quoted(_), Options)
 1405    ->  Options1 = Options
 1406    ;   '$merge_options'(_{quoted:true}, Options, Options1)
 1407    ),
 1408    format(string(String), '~W', [Term, Options1]).
 1409
 1410
 1411                 /*******************************
 1412                 *             GVAR             *
 1413                 *******************************/

nb_setval(+Name, +Value) is det: Bind the non-backtrackable variable Name with a copy of Value

 1419nb_setval(Name, Value) :-
 1420    duplicate_term(Value, Copy),
 1421    nb_linkval(Name, Copy).
 1422
 1423
 1424		 /*******************************
 1425		 *            THREADS		*
 1426		 *******************************/
 1427
 1428:- meta_predicate
 1429    thread_create(0, -).

thread_create(:Goal, -Id): Shorthand for thread_create(Goal, Id, []).

 1435thread_create(Goal, Id) :-
 1436    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.

 1445thread_join(Id) :-
 1446    thread_join(Id, Status),
 1447    (   Status == true
 1448    ->  true
 1449    ;   throw(error(thread_error(Id, Status), _))
 1450    ).

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.

 1460sig_block(Pattern) :-
 1461    (   nb_current('$sig_blocked', List)
 1462    ->  true
 1463    ;   List = []
 1464    ),
 1465    nb_setval('$sig_blocked', [Pattern|List]).
 1466
 1467sig_unblock(Pattern) :-
 1468    (   nb_current('$sig_blocked', List)
 1469    ->  unblock(List, Pattern, NewList),
 1470        (   List == NewList
 1471        ->  true
 1472        ;   nb_setval('$sig_blocked', NewList),
 1473            '$sig_unblock'
 1474        )
 1475    ;   true
 1476    ).
 1477
 1478unblock([], _, []).
 1479unblock([H|T], P, List) :-
 1480    (   subsumes_term(P, H)
 1481    ->  unblock(T, P, List)
 1482    ;   List = [H|T1],
 1483        unblock(T, P, T1)
 1484    ).
 1485
 1486:- public signal_is_blocked/1.          % called by signal_is_blocked()
 1487
 1488signal_is_blocked(Head) :-
 1489    nb_current('$sig_blocked', List),
 1490    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.

 1507set_prolog_gc_thread(Status) :-
 1508    var(Status),
 1509    !,
 1510    '$instantiation_error'(Status).
 1511set_prolog_gc_thread(_) :-
 1512    \+ current_prolog_flag(threads, true),
 1513    !.
 1514set_prolog_gc_thread(false) :-
 1515    !,
 1516    set_prolog_flag(gc_thread, false),
 1517    (   current_prolog_flag(threads, true)
 1518    ->  (   '$gc_stop'
 1519        ->  thread_join(gc)
 1520        ;   true
 1521        )
 1522    ;   true
 1523    ).
 1524set_prolog_gc_thread(true) :-
 1525    !,
 1526    set_prolog_flag(gc_thread, true).
 1527set_prolog_gc_thread(stop) :-
 1528    !,
 1529    (   current_prolog_flag(threads, true)
 1530    ->  (   '$gc_stop'
 1531        ->  thread_join(gc)
 1532        ;   true
 1533        )
 1534    ;   true
 1535    ).
 1536set_prolog_gc_thread(Status) :-
 1537    '$domain_error'(gc_thread, Status).

transaction(:Goal)
transaction(:Goal, +Options)
transaction(:Goal, :Constraint, +Mutex)
snapshot(:Goal): Wrappers to guarantee clean Module:Goal terms.

 1546transaction(Goal) :-
 1547    '$transaction'(Goal, []).
 1548transaction(Goal, Options) :-
 1549    '$transaction'(Goal, Options).
 1550transaction(Goal, Constraint, Mutex) :-
 1551    '$transaction'(Goal, Constraint, Mutex).
 1552snapshot(Goal) :-
 1553    '$snapshot'(Goal).
 1554
 1555
 1556		 /*******************************
 1557		 *            UNDO		*
 1558		 *******************************/
 1559
 1560:- meta_predicate
 1561    undo(0).

undo(:Goal): Schedule Goal to be called when backtracking takes us back to before this call.

 1568undo(Goal) :-
 1569    '$undo'(Goal).
 1570
 1571:- public
 1572    '$run_undo'/1. 1573
 1574'$run_undo'([One]) :-
 1575    !,
 1576    (   call(One)
 1577    ->  true
 1578    ;   true
 1579    ).
 1580'$run_undo'(List) :-
 1581    run_undo(List, _, Error),
 1582    (   var(Error)
 1583    ->  true
 1584    ;   throw(Error)
 1585    ).
 1586
 1587run_undo([], E, E).
 1588run_undo([H|T], E0, E) :-
 1589    (   catch(H, E1, true)
 1590    ->  (   var(E1)
 1591        ->  true
 1592        ;   '$urgent_exception'(E0, E1, E2)
 1593        )
 1594    ;   true
 1595    ),
 1596    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.

 1604:- meta_predicate
 1605    '$wrap_predicate'(:, +, -, -, +). 1606
 1607'$wrap_predicate'(M:Head, WName, Closure, call(Wrapped), Body) :-
 1608    callable_name_arguments(Head, PName, Args),
 1609    callable_name_arity(Head, PName, Arity),
 1610    (   is_most_general_term(Head)
 1611    ->  true
 1612    ;   '$domain_error'(most_general_term, Head)
 1613    ),
 1614    atomic_list_concat(['$wrap$', PName], WrapName),
 1615    PI = M:WrapName/Arity,
 1616    dynamic(PI),
 1617    '$notransact'(PI),
 1618    volatile(PI),
 1619    module_transparent(PI),
 1620    WHead =.. [WrapName|Args],
 1621    '$c_wrap_predicate'(M:Head, WName, Closure, Wrapped, M:(WHead :- Body)).
 1622
 1623callable_name_arguments(Head, PName, Args) :-
 1624    atom(Head),
 1625    !,
 1626    PName = Head,
 1627    Args = [].
 1628callable_name_arguments(Head, PName, Args) :-
 1629    compound_name_arguments(Head, PName, Args).
 1630
 1631callable_name_arity(Head, PName, Arity) :-
 1632    atom(Head),
 1633    !,
 1634    PName = Head,
 1635    Arity = 0.
 1636callable_name_arity(Head, PName, Arity) :-
 1637    compound_name_arity(Head, PName, Arity)