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 = 0.0 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    Time > 0.0.

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    (   '$c_current_predicate'(_, M:Head),
  276        predicate_property(M:Head, multifile)
  277    ->  multi_source_files(M:Head, Files),
  278        '$member'(File, Files)
  279    ;   '$source_file'(M:Head, File)
  280    ).
  281source_file(M:Head, File) :-
  282    (   nonvar(File)
  283    ->  true
  284    ;   source_file(File)
  285    ),
  286    '$source_file_predicates'(File, Predicates),
  287    '$member'(M:Head, Predicates).
  288
  289:- thread_local found_src_file/1.  290
  291multi_source_files(Head, Files) :-
  292    call_cleanup(
  293        findall(File, multi_source_file(Head, File), Files),
  294        retractall(found_src_file(_))).
  295
  296multi_source_file(Head, File) :-
  297    nth_clause(Head, _, Clause),
  298    clause_property(Clause, source(File)),
  299    \+ found_src_file(File),
  300    asserta(found_src_file(File)).

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

  307source_file_property(File, P) :-
  308    nonvar(File),
  309    !,
  310    canonical_source_file(File, Path),
  311    property_source_file(P, Path).
  312source_file_property(File, P) :-
  313    property_source_file(P, File).
  314
  315property_source_file(modified(Time), File) :-
  316    '$time_source_file'(File, Time, user).
  317property_source_file(source(Source), File) :-
  318    (   '$source_file_property'(File, from_state, true)
  319    ->  Source = state
  320    ;   '$source_file_property'(File, resource, true)
  321    ->  Source = resource
  322    ;   Source = file
  323    ).
  324property_source_file(module(M), File) :-
  325    (   nonvar(M)
  326    ->  '$current_module'(M, File)
  327    ;   nonvar(File)
  328    ->  '$current_module'(ML, File),
  329        (   atom(ML)
  330        ->  M = ML
  331        ;   '$member'(M, ML)
  332        )
  333    ;   '$current_module'(M, File)
  334    ).
  335property_source_file(load_context(Module, Location, Options), File) :-
  336    '$time_source_file'(File, _, user),
  337    clause(system:'$load_context_module'(File, Module, Options), true, Ref),
  338    (   clause_property(Ref, file(FromFile)),
  339        clause_property(Ref, line_count(FromLine))
  340    ->  Location = FromFile:FromLine
  341    ;   Location = user
  342    ).
  343property_source_file(includes(Master, Stamp), File) :-
  344    system:'$included'(File, _Line, Master, Stamp).
  345property_source_file(included_in(Master, Line), File) :-
  346    system:'$included'(Master, Line, File, _).
  347property_source_file(derived_from(DerivedFrom, Stamp), File) :-
  348    system:'$derived_source'(File, DerivedFrom, Stamp).
  349property_source_file(reloading, File) :-
  350    source_file(File),
  351    '$source_file_property'(File, reloading, true).
  352property_source_file(load_count(Count), File) :-
  353    source_file(File),
  354    '$source_file_property'(File, load_count, Count).
  355property_source_file(number_of_clauses(Count), File) :-
  356    source_file(File),
  357    '$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.

  364canonical_source_file(Spec, File) :-
  365    atom(Spec),
  366    '$time_source_file'(Spec, _, _),
  367    !,
  368    File = Spec.
  369canonical_source_file(Spec, File) :-
  370    system:'$included'(_Master, _Line, Spec, _),
  371    !,
  372    File = Spec.
  373canonical_source_file(Spec, File) :-
  374    absolute_file_name(Spec, File,
  375                       [ file_type(prolog),
  376                         access(read),
  377                         file_errors(fail)
  378                       ]),
  379    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.

  396exists_source(Source) :-
  397    exists_source(Source, _Path).
  398
  399exists_source(Source, Path) :-
  400    absolute_file_name(Source, Path,
  401                       [ file_type(prolog),
  402                         access(read),
  403                         file_errors(fail)
  404                       ]).

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.

  413prolog_load_context(module, Module) :-
  414    '$current_source_module'(Module).
  415prolog_load_context(file, File) :-
  416    input_file(File).
  417prolog_load_context(source, F) :-       % SICStus compatibility
  418    input_file(F0),
  419    '$input_context'(Context),
  420    '$top_file'(Context, F0, F).
  421prolog_load_context(stream, S) :-
  422    (   system:'$load_input'(_, S0)
  423    ->  S = S0
  424    ).
  425prolog_load_context(directory, D) :-
  426    input_file(F),
  427    file_directory_name(F, D).
  428prolog_load_context(dialect, D) :-
  429    current_prolog_flag(emulated_dialect, D).
  430prolog_load_context(term_position, TermPos) :-
  431    source_location(_, L),
  432    (   nb_current('$term_position', Pos),
  433        compound(Pos),              % actually set
  434        stream_position_data(line_count, Pos, L)
  435    ->  TermPos = Pos
  436    ;   TermPos = '$stream_position'(0,L,0,0)
  437    ).
  438prolog_load_context(script, Bool) :-
  439    (   '$toplevel':loaded_init_file(script, Path),
  440        input_file(File),
  441        same_file(File, Path)
  442    ->  Bool = true
  443    ;   Bool = false
  444    ).
  445prolog_load_context(variable_names, Bindings) :-
  446    (   nb_current('$variable_names', Bindings0)
  447    ->  Bindings = Bindings0
  448    ;   Bindings = []
  449    ).
  450prolog_load_context(term, Term) :-
  451    nb_current('$term', Term).
  452prolog_load_context(reloading, true) :-
  453    prolog_load_context(source, F),
  454    '$source_file_property'(F, reloading, true).
  455
  456input_file(File) :-
  457    (   system:'$load_input'(_, Stream)
  458    ->  stream_property(Stream, file_name(File))
  459    ),
  460    !.
  461input_file(File) :-
  462    source_location(File, _).

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

  469:- dynamic system:'$resolved_source_path'/2.  470
  471unload_file(File) :-
  472    (   canonical_source_file(File, Path)
  473    ->  '$unload_file'(Path),
  474        retractall(system:'$resolved_source_path'(_, Path))
  475    ;   true
  476    ).
  477
  478:- if(current_prolog_flag(open_shared_object, true)).  479
  480                 /*******************************
  481                 *            DLOPEN            *
  482                 *******************************/

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.

now Resolve all symbols in the file now instead of lazily.
global Make new symbols globally known.

  496open_shared_object(File, Handle) :-
  497    open_shared_object(File, Handle, []). % use pl-load.c defaults
  498
  499open_shared_object(File, Handle, Flags) :-
  500    (   is_list(Flags)
  501    ->  true
  502    ;   throw(error(type_error(list, Flags), _))
  503    ),
  504    map_dlflags(Flags, Mask),
  505    '$open_shared_object'(File, Handle, Mask).
  506
  507dlopen_flag(now,        2'01).          % see pl-load.c for these constants
  508dlopen_flag(global,     2'10).          % Solaris only
  509
  510map_dlflags([], 0).
  511map_dlflags([F|T], M) :-
  512    map_dlflags(T, M0),
  513    (   dlopen_flag(F, I)
  514    ->  true
  515    ;   throw(error(domain_error(dlopen_flag, F), _))
  516    ),
  517    M is M0 \/ I.
  518
  519:- export(open_shared_object/2).  520:- export(open_shared_object/3).  521
  522
  523		 /*******************************
  524		 *      FOREIGN LIBRARIES	*
  525		 *******************************/

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.

  544:- meta_predicate
  545    use_foreign_library(:),
  546    use_foreign_library(:, +).  547:- public
  548    use_foreign_library_noi/1.  549
  550use_foreign_library(FileSpec) :-
  551    ensure_shlib,
  552    initialization(use_foreign_library_noi(FileSpec), now).
  553
  554% noi -> no initialize; used by '$autoload':exports/3.
  555use_foreign_library_noi(FileSpec) :-
  556    ensure_shlib,
  557    shlib:load_foreign_library(FileSpec).
  558
  559use_foreign_library(FileSpec, Entry) :-
  560    ensure_shlib,
  561    initialization(shlib:load_foreign_library(FileSpec, Entry), now).
  562
  563ensure_shlib :-
  564    '$get_predicate_attribute'(shlib:load_foreign_library(_), defined, 1),
  565    '$get_predicate_attribute'(shlib:load_foreign_library(_,_), defined, 1),
  566    !.
  567ensure_shlib :-
  568    use_module(library(shlib), []).
  569
  570:- export(use_foreign_library/1).  571:- export(use_foreign_library/2).  572
  573:- elif(current_predicate('$activate_static_extension'/1)).  574
  575% Version when using shared objects is disabled and extensions are added
  576% as static libraries.
  577
  578:- meta_predicate
  579    use_foreign_library(:).  580:- public
  581    use_foreign_library_noi/1.  582:- dynamic
  583    loading/1,
  584    foreign_predicate/2.  585
  586use_foreign_library(FileSpec) :-
  587    initialization(use_foreign_library_noi(FileSpec), now).
  588
  589use_foreign_library_noi(Module:foreign(Extension)) :-
  590    setup_call_cleanup(
  591        asserta(loading(foreign(Extension)), Ref),
  592        @('$activate_static_extension'(Extension), Module),
  593        erase(Ref)).
  594
  595:- export(use_foreign_library/1).  596
  597system:'$foreign_registered'(M, H) :-
  598    (   loading(Lib)
  599    ->  true
  600    ;   Lib = '<spontaneous>'
  601    ),
  602    assert(foreign_predicate(Lib, M:H)).

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

  608current_foreign_library(File, Public) :-
  609    setof(Pred, foreign_predicate(File, Pred), Public).
  610
  611:- export(current_foreign_library/2).  612
  613:- endif. /* open_shared_object support */
  614
  615                 /*******************************
  616                 *            STREAMS           *
  617                 *******************************/

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

  624stream_position_data(Prop, Term, Value) :-
  625    nonvar(Prop),
  626    !,
  627    (   stream_position_field(Prop, Pos)
  628    ->  arg(Pos, Term, Value)
  629    ;   throw(error(domain_error(stream_position_data, Prop)))
  630    ).
  631stream_position_data(Prop, Term, Value) :-
  632    stream_position_field(Prop, Pos),
  633    arg(Pos, Term, Value).
  634
  635stream_position_field(char_count,    1).
  636stream_position_field(line_count,    2).
  637stream_position_field(line_position, 3).
  638stream_position_field(byte_count,    4).
  639
  640
  641                 /*******************************
  642                 *            CONTROL           *
  643                 *******************************/

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.

  651:- meta_predicate
  652    call_with_depth_limit(0, +, -).  653
  654call_with_depth_limit(G, Limit, Result) :-
  655    '$depth_limit'(Limit, OLimit, OReached),
  656    (   catch(G, E, '$depth_limit_except'(OLimit, OReached, E)),
  657        '$depth_limit_true'(Limit, OLimit, OReached, Result, Det),
  658        ( Det == ! -> ! ; true )
  659    ;   '$depth_limit_false'(OLimit, OReached, Result)
  660    ).

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.

  673:- meta_predicate
  674    call_with_inference_limit(0, +, -).  675
  676call_with_inference_limit(G, Limit, Result) :-
  677    '$inference_limit'(Limit, OLimit),
  678    (   catch(G, Except,
  679              system:'$inference_limit_except'(OLimit, Except, Result0)),
  680        (   Result0 == inference_limit_exceeded
  681        ->  !
  682        ;   system:'$inference_limit_true'(Limit, OLimit, Result0),
  683            ( Result0 == ! -> ! ; true )
  684        ),
  685        Result = Result0
  686    ;   system:'$inference_limit_false'(OLimit)
  687    ).
  688
  689
  690                /********************************
  691                *           DATA BASE           *
  692                *********************************/
  693
  694/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  695The predicate current_predicate/2 is   a  difficult subject since  the
  696introduction  of defaulting     modules   and   dynamic     libraries.
  697current_predicate/2 is normally  called with instantiated arguments to
  698verify some  predicate can   be called without trapping   an undefined
  699predicate.  In this case we must  perform the search algorithm used by
  700the prolog system itself.
  701
  702If the pattern is not fully specified, we only generate the predicates
  703actually available in this  module.   This seems the best for listing,
  704etc.
  705- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  706
  707
  708:- meta_predicate
  709    current_predicate(?, :),
  710    '$defined_predicate'(:).  711
  712current_predicate(Name, Module:Head) :-
  713    (var(Module) ; var(Head)),
  714    !,
  715    generate_current_predicate(Name, Module, Head).
  716current_predicate(Name, Term) :-
  717    '$c_current_predicate'(Name, Term),
  718    '$defined_predicate'(Term),
  719    !.
  720current_predicate(Name, Module:Head) :-
  721    default_module(Module, DefModule),
  722    '$c_current_predicate'(Name, DefModule:Head),
  723    '$defined_predicate'(DefModule:Head),
  724    !.
  725current_predicate(Name, Module:Head) :-
  726    '$autoload':autoload_in(Module, general),
  727    \+ current_prolog_flag(Module:unknown, fail),
  728    (   compound(Head)
  729    ->  compound_name_arity(Head, Name, Arity)
  730    ;   Name = Head, Arity = 0
  731    ),
  732    '$find_library'(Module, Name, Arity, _LoadModule, _Library),
  733    !.
  734
  735generate_current_predicate(Name, Module, Head) :-
  736    current_module(Module),
  737    QHead = Module:Head,
  738    '$c_current_predicate'(Name, QHead),
  739    '$get_predicate_attribute'(QHead, defined, 1).
  740
  741'$defined_predicate'(Head) :-
  742    '$get_predicate_attribute'(Head, defined, 1),
  743    !.

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

  749:- meta_predicate
  750    predicate_property(:, ?).  751
  752:- multifile
  753    '$predicate_property'/2.  754
  755:- '$iso'(predicate_property/2).  756
  757predicate_property(Pred, Property) :-           % Mode ?,+
  758    nonvar(Property),
  759    !,
  760    property_predicate(Property, Pred).
  761predicate_property(Pred, Property) :-           % Mode +,-
  762    define_or_generate(Pred),
  763    '$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.

  771property_predicate(undefined, Pred) :-
  772    !,
  773    Pred = Module:Head,
  774    current_module(Module),
  775    '$c_current_predicate'(_, Pred),
  776    \+ '$defined_predicate'(Pred),          % Speed up a bit
  777    \+ current_predicate(_, Pred),
  778    goal_name_arity(Head, Name, Arity),
  779    \+ system_undefined(Module:Name/Arity).
  780property_predicate(visible, Pred) :-
  781    !,
  782    visible_predicate(Pred).
  783property_predicate(autoload(File), Head) :-
  784    !,
  785    \+ current_prolog_flag(autoload, false),
  786    '$autoload':autoloadable(Head, File).
  787property_predicate(implementation_module(IM), M:Head) :-
  788    !,
  789    atom(M),
  790    (   default_module(M, DM),
  791        '$get_predicate_attribute'(DM:Head, defined, 1)
  792    ->  (   '$get_predicate_attribute'(DM:Head, imported, ImportM)
  793        ->  IM = ImportM
  794        ;   IM = M
  795        )
  796    ;   \+ current_prolog_flag(M:unknown, fail),
  797        goal_name_arity(Head, Name, Arity),
  798        '$find_library'(_, Name, Arity, LoadModule, _File)
  799    ->  IM = LoadModule
  800    ;   M = IM
  801    ).
  802property_predicate(iso, _:Head) :-
  803    callable(Head),
  804    !,
  805    goal_name_arity(Head, Name, Arity),
  806    current_predicate(system:Name/Arity),
  807    '$predicate_property'(iso, system:Head).
  808property_predicate(built_in, Module:Head) :-
  809    callable(Head),
  810    !,
  811    goal_name_arity(Head, Name, Arity),
  812    current_predicate(Module:Name/Arity),
  813    '$predicate_property'(built_in, Module:Head).
  814property_predicate(Property, Pred) :-
  815    define_or_generate(Pred),
  816    '$predicate_property'(Property, Pred).
  817
  818goal_name_arity(Head, Name, Arity) :-
  819    compound(Head),
  820    !,
  821    compound_name_arity(Head, Name, Arity).
  822goal_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.

  831define_or_generate(M:Head) :-
  832    callable(Head),
  833    atom(M),
  834    '$get_predicate_attribute'(M:Head, defined, 1),
  835    !.
  836define_or_generate(M:Head) :-
  837    callable(Head),
  838    nonvar(M), M \== system,
  839    !,
  840    '$define_predicate'(M:Head).
  841define_or_generate(Pred) :-
  842    current_predicate(_, Pred),
  843    '$define_predicate'(Pred).
  844
  845
  846'$predicate_property'(interpreted, Pred) :-
  847    '$get_predicate_attribute'(Pred, foreign, 0).
  848'$predicate_property'(visible, Pred) :-
  849    '$get_predicate_attribute'(Pred, defined, 1).
  850'$predicate_property'(built_in, Pred) :-
  851    '$get_predicate_attribute'(Pred, system, 1).
  852'$predicate_property'(exported, Pred) :-
  853    '$get_predicate_attribute'(Pred, exported, 1).
  854'$predicate_property'(public, Pred) :-
  855    '$get_predicate_attribute'(Pred, public, 1).
  856'$predicate_property'(non_terminal, Pred) :-
  857    '$get_predicate_attribute'(Pred, non_terminal, 1).
  858'$predicate_property'(foreign, Pred) :-
  859    '$get_predicate_attribute'(Pred, foreign, 1).
  860'$predicate_property'((dynamic), Pred) :-
  861    '$get_predicate_attribute'(Pred, (dynamic), 1).
  862'$predicate_property'((static), Pred) :-
  863    '$get_predicate_attribute'(Pred, (dynamic), 0).
  864'$predicate_property'((volatile), Pred) :-
  865    '$get_predicate_attribute'(Pred, (volatile), 1).
  866'$predicate_property'((thread_local), Pred) :-
  867    '$get_predicate_attribute'(Pred, (thread_local), 1).
  868'$predicate_property'((multifile), Pred) :-
  869    '$get_predicate_attribute'(Pred, (multifile), 1).
  870'$predicate_property'((discontiguous), Pred) :-
  871    '$get_predicate_attribute'(Pred, (discontiguous), 1).
  872'$predicate_property'(imported_from(Module), Pred) :-
  873    '$get_predicate_attribute'(Pred, imported, Module).
  874'$predicate_property'(transparent, Pred) :-
  875    '$get_predicate_attribute'(Pred, transparent, 1).
  876'$predicate_property'(meta_predicate(Pattern), Pred) :-
  877    '$get_predicate_attribute'(Pred, meta_predicate, Pattern).
  878'$predicate_property'(file(File), Pred) :-
  879    '$get_predicate_attribute'(Pred, file, File).
  880'$predicate_property'(line_count(LineNumber), Pred) :-
  881    '$get_predicate_attribute'(Pred, line_count, LineNumber).
  882'$predicate_property'(notrace, Pred) :-
  883    '$get_predicate_attribute'(Pred, trace, 0).
  884'$predicate_property'(nodebug, Pred) :-
  885    '$get_predicate_attribute'(Pred, hide_childs, 1).
  886'$predicate_property'(spying, Pred) :-
  887    '$get_predicate_attribute'(Pred, spy, 1).
  888'$predicate_property'(number_of_clauses(N), Pred) :-
  889    '$get_predicate_attribute'(Pred, number_of_clauses, N).
  890'$predicate_property'(number_of_rules(N), Pred) :-
  891    '$get_predicate_attribute'(Pred, number_of_rules, N).
  892'$predicate_property'(last_modified_generation(Gen), Pred) :-
  893    '$get_predicate_attribute'(Pred, last_modified_generation, Gen).
  894'$predicate_property'(indexed(Indices), Pred) :-
  895    '$get_predicate_attribute'(Pred, indexed, Indices).
  896'$predicate_property'(noprofile, Pred) :-
  897    '$get_predicate_attribute'(Pred, noprofile, 1).
  898'$predicate_property'(ssu, Pred) :-
  899    '$get_predicate_attribute'(Pred, ssu, 1).
  900'$predicate_property'(iso, Pred) :-
  901    '$get_predicate_attribute'(Pred, iso, 1).
  902'$predicate_property'(det, Pred) :-
  903    '$get_predicate_attribute'(Pred, det, 1).
  904'$predicate_property'(sig_atomic, Pred) :-
  905    '$get_predicate_attribute'(Pred, sig_atomic, 1).
  906'$predicate_property'(quasi_quotation_syntax, Pred) :-
  907    '$get_predicate_attribute'(Pred, quasi_quotation_syntax, 1).
  908'$predicate_property'(defined, Pred) :-
  909    '$get_predicate_attribute'(Pred, defined, 1).
  910'$predicate_property'(tabled, Pred) :-
  911    '$get_predicate_attribute'(Pred, tabled, 1).
  912'$predicate_property'(tabled(Flag), Pred) :-
  913    '$get_predicate_attribute'(Pred, tabled, 1),
  914    table_flag(Flag, Pred).
  915'$predicate_property'(incremental, Pred) :-
  916    '$get_predicate_attribute'(Pred, incremental, 1).
  917'$predicate_property'(monotonic, Pred) :-
  918    '$get_predicate_attribute'(Pred, monotonic, 1).
  919'$predicate_property'(opaque, Pred) :-
  920    '$get_predicate_attribute'(Pred, opaque, 1).
  921'$predicate_property'(lazy, Pred) :-
  922    '$get_predicate_attribute'(Pred, lazy, 1).
  923'$predicate_property'(abstract(N), Pred) :-
  924    '$get_predicate_attribute'(Pred, abstract, N).
  925'$predicate_property'(size(Bytes), Pred) :-
  926    '$get_predicate_attribute'(Pred, size, Bytes).
  927
  928system_undefined(user:prolog_trace_interception/4).
  929system_undefined(prolog:prolog_exception_hook/5).
  930system_undefined(system:'$c_call_prolog'/0).
  931system_undefined(system:window_title/2).
  932
  933table_flag(variant, Pred) :-
  934    '$tbl_implementation'(Pred, M:Head),
  935    M:'$tabled'(Head, variant).
  936table_flag(subsumptive, Pred) :-
  937    '$tbl_implementation'(Pred, M:Head),
  938    M:'$tabled'(Head, subsumptive).
  939table_flag(shared, Pred) :-
  940    '$get_predicate_attribute'(Pred, tshared, 1).
  941table_flag(incremental, Pred) :-
  942    '$get_predicate_attribute'(Pred, incremental, 1).
  943table_flag(monotonic, Pred) :-
  944    '$get_predicate_attribute'(Pred, monotonic, 1).
  945table_flag(subgoal_abstract(N), Pred) :-
  946    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  947table_flag(answer_abstract(N), Pred) :-
  948    '$get_predicate_attribute'(Pred, subgoal_abstract, N).
  949table_flag(subgoal_abstract(N), Pred) :-
  950    '$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.

  959visible_predicate(Pred) :-
  960    Pred = M:Head,
  961    current_module(M),
  962    (   callable(Head)
  963    ->  (   '$get_predicate_attribute'(Pred, defined, 1)
  964        ->  true
  965        ;   \+ current_prolog_flag(M:unknown, fail),
  966            '$head_name_arity'(Head, Name, Arity),
  967            '$find_library'(M, Name, Arity, _LoadModule, _Library)
  968        )
  969    ;   setof(PI, visible_in_module(M, PI), PIs),
  970        '$member'(Name/Arity, PIs),
  971        functor(Head, Name, Arity)
  972    ).
  973
  974visible_in_module(M, Name/Arity) :-
  975    default_module(M, DefM),
  976    DefHead = DefM:Head,
  977    '$c_current_predicate'(_, DefHead),
  978    '$get_predicate_attribute'(DefHead, defined, 1),
  979    \+ hidden_system_predicate(Head),
  980    functor(Head, Name, Arity).
  981visible_in_module(_, Name/Arity) :-
  982    '$in_library'(Name, Arity, _).
  983
  984hidden_system_predicate(Head) :-
  985    functor(Head, Name, _),
  986    atom(Name),                     % Avoid [].
  987    sub_atom(Name, 0, _, _, $),
  988    \+ 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.

 1013clause_property(Clause, Property) :-
 1014    '$clause_property'(Property, Clause).
 1015
 1016'$clause_property'(line_count(LineNumber), Clause) :-
 1017    '$get_clause_attribute'(Clause, line_count, LineNumber).
 1018'$clause_property'(file(File), Clause) :-
 1019    '$get_clause_attribute'(Clause, file, File).
 1020'$clause_property'(source(File), Clause) :-
 1021    '$get_clause_attribute'(Clause, owner, File).
 1022'$clause_property'(size(Bytes), Clause) :-
 1023    '$get_clause_attribute'(Clause, size, Bytes).
 1024'$clause_property'(fact, Clause) :-
 1025    '$get_clause_attribute'(Clause, fact, true).
 1026'$clause_property'(erased, Clause) :-
 1027    '$get_clause_attribute'(Clause, erased, true).
 1028'$clause_property'(predicate(PI), Clause) :-
 1029    '$get_clause_attribute'(Clause, predicate_indicator, PI).
 1030'$clause_property'(module(M), Clause) :-
 1031    '$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)

 1045dynamic(M:Predicates, Options) :-
 1046    '$must_be'(list, Predicates),
 1047    options_properties(Options, Props),
 1048    set_pprops(Predicates, M, [dynamic|Props]).
 1049
 1050set_pprops([], _, _).
 1051set_pprops([H|T], M, Props) :-
 1052    set_pprops1(Props, M:H),
 1053    strip_module(M:H, M2, P),
 1054    '$pi_head'(M2:P, Pred),
 1055    '$set_table_wrappers'(Pred),
 1056    set_pprops(T, M, Props).
 1057
 1058set_pprops1([], _).
 1059set_pprops1([H|T], P) :-
 1060    (   atom(H)
 1061    ->  '$set_predicate_attribute'(P, H, true)
 1062    ;   H =.. [Name,Value]
 1063    ->  '$set_predicate_attribute'(P, Name, Value)
 1064    ),
 1065    set_pprops1(T, P).
 1066
 1067options_properties(Options, Props) :-
 1068    G = opt_prop(_,_,_,_),
 1069    findall(G, G, Spec),
 1070    options_properties(Spec, Options, Props).
 1071
 1072options_properties([], _, []).
 1073options_properties([opt_prop(Name, Type, SetValue, Prop)|T],
 1074                   Options, [Prop|PT]) :-
 1075    Opt =.. [Name,V],
 1076    '$option'(Opt, Options),
 1077    '$must_be'(Type, V),
 1078    V = SetValue,
 1079    !,
 1080    options_properties(T, Options, PT).
 1081options_properties([_|T], Options, PT) :-
 1082    options_properties(T, Options, PT).
 1083
 1084opt_prop(incremental,   boolean,               Bool,  incremental(Bool)).
 1085opt_prop(abstract,      between(0,0),          0,     abstract).
 1086opt_prop(multifile,     boolean,               true,  multifile).
 1087opt_prop(discontiguous, boolean,               true,  discontiguous).
 1088opt_prop(volatile,      boolean,               true,  volatile).
 1089opt_prop(thread,        oneof(atom, [local,shared],[local,shared]),
 1090                                               local, thread_local).
 1091
 1092                /********************************
 1093                *            MODULES            *
 1094                *********************************/

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

 1100current_module(Module) :-
 1101    '$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.

 1117module_property(Module, Property) :-
 1118    nonvar(Module), nonvar(Property),
 1119    !,
 1120    property_module(Property, Module).
 1121module_property(Module, Property) :-    % -, file(File)
 1122    nonvar(Property), Property = file(File),
 1123    !,
 1124    (   nonvar(File)
 1125    ->  '$current_module'(Modules, File),
 1126        (   atom(Modules)
 1127        ->  Module = Modules
 1128        ;   '$member'(Module, Modules)
 1129        )
 1130    ;   '$current_module'(Module, File),
 1131        File \== []
 1132    ).
 1133module_property(Module, Property) :-
 1134    current_module(Module),
 1135    property_module(Property, Module).
 1136
 1137property_module(Property, Module) :-
 1138    module_property(Property),
 1139    (   Property = exported_operators(List)
 1140    ->  '$exported_ops'(Module, List, [])
 1141    ;   '$module_property'(Module, Property)
 1142    ).
 1143
 1144module_property(class(_)).
 1145module_property(file(_)).
 1146module_property(line_count(_)).
 1147module_property(exports(_)).
 1148module_property(exported_operators(_)).
 1149module_property(size(_)).
 1150module_property(program_size(_)).
 1151module_property(program_space(_)).
 1152module_property(last_modified_generation(_)).

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

 1158module(Module) :-
 1159    atom(Module),
 1160    current_module(Module),
 1161    !,
 1162    '$set_typein_module'(Module).
 1163module(Module) :-
 1164    '$set_typein_module'(Module),
 1165    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.

 1172working_directory(Old, New) :-
 1173    '$cwd'(Old),
 1174    (   Old == New
 1175    ->  true
 1176    ;   '$chdir'(New)
 1177    ).
 1178
 1179
 1180                 /*******************************
 1181                 *            TRIES             *
 1182                 *******************************/

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

 1188current_trie(Trie) :-
 1189    current_blob(Trie, trie),
 1190    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

 1226trie_property(Trie, Property) :-
 1227    current_trie(Trie),
 1228    trie_property(Property),
 1229    '$trie_property'(Trie, Property).
 1230
 1231trie_property(node_count(_)).
 1232trie_property(value_count(_)).
 1233trie_property(size(_)).
 1234trie_property(hashed(_)).
 1235trie_property(compiled_size(_)).
 1236                                                % below only when -DO_TRIE_STATS
 1237trie_property(lookup_count(_)).                 % is enabled in pl-trie.h
 1238trie_property(gen_call_count(_)).
 1239trie_property(invalidated(_)).                  % IDG stats
 1240trie_property(reevaluated(_)).
 1241trie_property(deadlock(_)).                     % Shared tabling stats
 1242trie_property(wait(_)).
 1243trie_property(idg_affected_count(_)).
 1244trie_property(idg_dependent_count(_)).
 1245trie_property(idg_size(_)).
 1246
 1247
 1248                /********************************
 1249                *      SYSTEM INTERACTION       *
 1250                *********************************/
 1251
 1252shell(Command) :-
 1253    shell(Command, 0).
 1254
 1255
 1256                 /*******************************
 1257                 *            SIGNALS           *
 1258                 *******************************/
 1259
 1260:- meta_predicate
 1261    on_signal(+, :, :),
 1262    current_signal(?, ?, :).

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

 1266on_signal(Signal, Old, New) :-
 1267    atom(Signal),
 1268    !,
 1269    '$on_signal'(_Num, Signal, Old, New).
 1270on_signal(Signal, Old, New) :-
 1271    integer(Signal),
 1272    !,
 1273    '$on_signal'(Signal, _Name, Old, New).
 1274on_signal(Signal, _Old, _New) :-
 1275    '$type_error'(signal_name, Signal).

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

 1279current_signal(Name, Id, Handler) :-
 1280    between(1, 32, Id),
 1281    '$on_signal'(Id, Name, Handler, Handler).
 1282
 1283:- multifile
 1284    prolog:called_by/2. 1285
 1286prolog:called_by(on_signal(_,_,New), [New+1]) :-
 1287    (   new == throw
 1288    ;   new == default
 1289    ), !, fail.
 1290
 1291
 1292                 /*******************************
 1293                 *             I/O              *
 1294                 *******************************/
 1295
 1296format(Fmt) :-
 1297    format(Fmt, []).
 1298
 1299                 /*******************************
 1300                 *            FILES             *
 1301                 *******************************/

absolute_file_name(+Term, -AbsoluteFile)

 1305absolute_file_name(Name, Abs) :-
 1306    atomic(Name),
 1307    !,
 1308    '$absolute_file_name'(Name, Abs).
 1309absolute_file_name(Term, Abs) :-
 1310    '$chk_file'(Term, [''], [access(read)], true, File),
 1311    !,
 1312    '$absolute_file_name'(File, Abs).
 1313absolute_file_name(Term, Abs) :-
 1314    '$chk_file'(Term, [''], [], true, File),
 1315    !,
 1316    '$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.

 1324tmp_file_stream(Enc, File, Stream) :-
 1325    atom(Enc), var(File), var(Stream),
 1326    !,
 1327    '$tmp_file_stream'('', Enc, File, Stream).
 1328tmp_file_stream(File, Stream, Options) :-
 1329    current_prolog_flag(encoding, DefEnc),
 1330    '$option'(encoding(Enc), Options, DefEnc),
 1331    '$option'(extension(Ext), Options, ''),
 1332    '$tmp_file_stream'(Ext, Enc, File, Stream),
 1333    set_stream(Stream, file_name(File)).
 1334
 1335
 1336                /********************************
 1337                *        MEMORY MANAGEMENT      *
 1338                *********************************/

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.

 1347garbage_collect :-
 1348    '$garbage_collect'(0).

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

 1354set_prolog_stack(Stack, Option) :-
 1355    Option =.. [Name,Value0],
 1356    Value is Value0,
 1357    '$set_prolog_stack'(Stack, Name, _Old, Value).

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

 1363prolog_stack_property(Stack, Property) :-
 1364    stack_property(P),
 1365    stack_name(Stack),
 1366    Property =.. [P,Value],
 1367    '$set_prolog_stack'(Stack, P, Value, Value).
 1368
 1369stack_name(local).
 1370stack_name(global).
 1371stack_name(trail).
 1372
 1373stack_property(limit).
 1374stack_property(spare).
 1375stack_property(min_free).
 1376stack_property(low).
 1377stack_property(factor).
 1378
 1379
 1380		 /*******************************
 1381		 *            CLAUSE		*
 1382		 *******************************/

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.

 1390rule(Head, Rule) :-
 1391    '$rule'(Head, Rule0),
 1392    conditional_rule(Rule0, Rule1),
 1393    Rule = Rule1.
 1394rule(Head, Rule, Ref) :-
 1395    '$rule'(Head, Rule0, Ref),
 1396    conditional_rule(Rule0, Rule1),
 1397    Rule = Rule1.
 1398
 1399conditional_rule(?=>(Head, (!, Body)), Rule) =>
 1400    Rule = (Head => Body).
 1401conditional_rule(?=>(Head, !), Rule) =>
 1402    Rule = (Head => true).
 1403conditional_rule(?=>(Head, Body0), Rule),
 1404    split_on_cut(Body0, Cond, Body) =>
 1405    Rule = (Head,Cond=>Body).
 1406conditional_rule(Head, Rule) =>
 1407    Rule = Head.
 1408
 1409split_on_cut((Cond0,!,Body0), Cond, Body) =>
 1410    Cond = Cond0,
 1411    Body = Body0.
 1412split_on_cut((!,Body0), Cond, Body) =>
 1413    Cond = true,
 1414    Body = Body0.
 1415split_on_cut((A,B), Cond, Body) =>
 1416    Cond = (A,Cond1),
 1417    split_on_cut(B, Cond1, Body).
 1418split_on_cut(_, _, _) =>
 1419    fail.
 1420
 1421
 1422                 /*******************************
 1423                 *             TERM             *
 1424                 *******************************/
 1425
 1426:- '$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.

 1434numbervars(Term, From, To) :-
 1435    numbervars(Term, From, To, []).
 1436
 1437
 1438                 /*******************************
 1439                 *            STRING            *
 1440                 *******************************/

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

 1446term_string(Term, String, Options) :-
 1447    nonvar(String),
 1448    !,
 1449    read_term_from_atom(String, Term, Options).
 1450term_string(Term, String, Options) :-
 1451    (   '$option'(quoted(_), Options)
 1452    ->  Options1 = Options
 1453    ;   '$merge_options'(_{quoted:true}, Options, Options1)
 1454    ),
 1455    format(string(String), '~W', [Term, Options1]).
 1456
 1457
 1458                 /*******************************
 1459                 *             GVAR             *
 1460                 *******************************/

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

 1466nb_setval(Name, Value) :-
 1467    duplicate_term(Value, Copy),
 1468    nb_linkval(Name, Copy).
 1469
 1470
 1471		 /*******************************
 1472		 *            THREADS		*
 1473		 *******************************/
 1474
 1475:- meta_predicate
 1476    thread_create(0, -).

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

 1482thread_create(Goal, Id) :-
 1483    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.

 1492thread_join(Id) :-
 1493    thread_join(Id, Status),
 1494    (   Status == true
 1495    ->  true
 1496    ;   throw(error(thread_error(Id, Status), _))
 1497    ).

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.

 1507sig_block(Pattern) :-
 1508    (   nb_current('$sig_blocked', List)
 1509    ->  true
 1510    ;   List = []
 1511    ),
 1512    nb_setval('$sig_blocked', [Pattern|List]).
 1513
 1514sig_unblock(Pattern) :-
 1515    (   nb_current('$sig_blocked', List)
 1516    ->  unblock(List, Pattern, NewList),
 1517        (   List == NewList
 1518        ->  true
 1519        ;   nb_setval('$sig_blocked', NewList),
 1520            '$sig_unblock'
 1521        )
 1522    ;   true
 1523    ).
 1524
 1525unblock([], _, []).
 1526unblock([H|T], P, List) :-
 1527    (   subsumes_term(P, H)
 1528    ->  unblock(T, P, List)
 1529    ;   List = [H|T1],
 1530        unblock(T, P, T1)
 1531    ).
 1532
 1533:- public signal_is_blocked/1.          % called by signal_is_blocked()
 1534
 1535signal_is_blocked(Head) :-
 1536    nb_current('$sig_blocked', List),
 1537    '$member'(Head, List),
 1538    !.

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.

 1555set_prolog_gc_thread(Status) :-
 1556    var(Status),
 1557    !,
 1558    '$instantiation_error'(Status).
 1559set_prolog_gc_thread(false) :-
 1560    !,
 1561    set_prolog_flag(gc_thread, false),
 1562    (   current_prolog_flag(threads, true)
 1563    ->  (   '$gc_stop'
 1564        ->  thread_join(gc)
 1565        ;   true
 1566        )
 1567    ;   true
 1568    ).
 1569set_prolog_gc_thread(true) :-
 1570    !,
 1571    set_prolog_flag(gc_thread, true).
 1572set_prolog_gc_thread(stop) :-
 1573    !,
 1574    (   current_prolog_flag(threads, true)
 1575    ->  (   '$gc_stop'
 1576        ->  thread_join(gc)
 1577        ;   true
 1578        )
 1579    ;   true
 1580    ).
 1581set_prolog_gc_thread(Status) :-
 1582    '$domain_error'(gc_thread, Status).

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

 1591transaction(Goal) :-
 1592    '$transaction'(Goal, []).
 1593transaction(Goal, Options) :-
 1594    '$transaction'(Goal, Options).
 1595transaction(Goal, Constraint, Mutex) :-
 1596    '$transaction'(Goal, Constraint, Mutex).
 1597snapshot(Goal) :-
 1598    '$snapshot'(Goal).
 1599
 1600
 1601		 /*******************************
 1602		 *            UNDO		*
 1603		 *******************************/
 1604
 1605:- meta_predicate
 1606    undo(0).

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

 1613undo(Goal) :-
 1614    '$undo'(Goal).
 1615
 1616:- public
 1617    '$run_undo'/1. 1618
 1619'$run_undo'([One]) :-
 1620    !,
 1621    call(One).
 1622'$run_undo'(List) :-
 1623    run_undo(List, _, Error),
 1624    (   var(Error)
 1625    ->  true
 1626    ;   throw(Error)
 1627    ).
 1628
 1629run_undo([], E, E).
 1630run_undo([H|T], E0, E) :-
 1631    (   catch(H, E1, true)
 1632    ->  (   var(E1)
 1633        ->  true
 1634        ;   '$urgent_exception'(E0, E1, E2)
 1635        )
 1636    ;   true
 1637    ),
 1638    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.

 1646:- meta_predicate
 1647    '$wrap_predicate'(:, +, -, -, +). 1648
 1649'$wrap_predicate'(M:Head, WName, Closure, call(Wrapped), Body) :-
 1650    callable_name_arguments(Head, PName, Args),
 1651    callable_name_arity(Head, PName, Arity),
 1652    (   is_most_general_term(Head)
 1653    ->  true
 1654    ;   '$domain_error'(most_general_term, Head)
 1655    ),
 1656    atomic_list_concat(['$wrap$', PName], WrapName),
 1657    volatile(M:WrapName/Arity),
 1658    module_transparent(M:WrapName/Arity),
 1659    WHead =.. [WrapName|Args],
 1660    '$c_wrap_predicate'(M:Head, WName, Closure, Wrapped, M:(WHead :- Body)).
 1661
 1662callable_name_arguments(Head, PName, Args) :-
 1663    atom(Head),
 1664    !,
 1665    PName = Head,
 1666    Args = [].
 1667callable_name_arguments(Head, PName, Args) :-
 1668    compound_name_arguments(Head, PName, Args).
 1669
 1670callable_name_arity(Head, PName, Arity) :-
 1671    atom(Head),
 1672    !,
 1673    PName = Head,
 1674    Arity = 0.
 1675callable_name_arity(Head, PName, Arity) :-
 1676    compound_name_arity(Head, PName, Arity)