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)  1985-2020, University of Amsterdam
    7                              VU University Amsterdam
    8                              CWI, Amsterdam
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module('$syspreds',
   38          [ leash/1,
   39            visible/1,
   40            style_check/1,
   41            (spy)/1,
   42            (nospy)/1,
   43            nospyall/0,
   44            debugging/0,
   45            flag/3,
   46            atom_prefix/2,
   47            dwim_match/2,
   48            source_file_property/2,
   49            source_file/1,
   50            source_file/2,
   51            unload_file/1,
   52            exists_source/1,                    % +Spec
   53            exists_source/2,                    % +Spec, -Path
   54            use_foreign_library/1,		% :FileSpec
   55            use_foreign_library/2,		% :FileSpec, +Install
   56            prolog_load_context/2,
   57            stream_position_data/3,
   58            current_predicate/2,
   59            '$defined_predicate'/1,
   60            predicate_property/2,
   61            '$predicate_property'/2,
   62            (dynamic)/2,                        % :Predicates, +Options
   63            clause_property/2,
   64            current_module/1,                   % ?Module
   65            module_property/2,                  % ?Module, ?Property
   66            module/1,                           % +Module
   67            current_trie/1,                     % ?Trie
   68            trie_property/2,                    % ?Trie, ?Property
   69            working_directory/2,                % -OldDir, +NewDir
   70            shell/1,                            % +Command
   71            on_signal/3,
   72            current_signal/3,
   73            open_shared_object/2,
   74            open_shared_object/3,
   75            format/1,
   76            garbage_collect/0,
   77            set_prolog_stack/2,
   78            prolog_stack_property/2,
   79            absolute_file_name/2,
   80            tmp_file_stream/3,                  % +Enc, -File, -Stream
   81            call_with_depth_limit/3,            % :Goal, +Limit, -Result
   82            call_with_inference_limit/3,        % :Goal, +Limit, -Result
   83            numbervars/3,                       % +Term, +Start, -End
   84            term_string/3,                      % ?Term, ?String, +Options
   85            nb_setval/2,                        % +Var, +Value
   86            thread_create/2,                    % :Goal, -Id
   87            thread_join/1,                      % +Id
   88            transaction/1,                      % :Goal
   89            transaction/2,                      % :Goal, +Options
   90            transaction/3,                      % :Goal, :Constraint, +Mutex
   91            snapshot/1,                         % :Goal
   92            set_prolog_gc_thread/1,		% +Status
   93
   94            '$wrap_predicate'/5                 % :Head, +Name, -Closure, -Wrapped, +Body
   95          ]).   96
   97:- meta_predicate
   98    dynamic(:, +),
   99    use_foreign_library(:),
  100    use_foreign_library(:, +),
  101    transaction(0),
  102    transaction(0,0,+),
  103    snapshot(0).  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.

prolog:debug_control_hook(+Action): Allow user-hooks in the Prolog debugger interaction. See the calls below for the provided hooks. We use a single predicate with action argument to avoid an uncontrolled poliferation of hooks.

  210:- multifile
  211    prolog:debug_control_hook/1.    % +Action
  212
  213:- meta_predicate
  214    spy(:),
  215    nospy(:).

spy(:Spec) is det

nospy(:Spec) is det

nospyall is det

Set/clear spy-points. A successfully set or cleared spy-point is reported using print_message/2, level informational, with one of the following terms, where Spec is of the form M:Head.

spy(Spec)
nospy(Spec)

See also: - spy/1 and nospy/1 call the hook debug_control_hook/1 to allow for alternative specifications of the thing to debug.

  232spy(_:X) :-
  233    var(X),
  234    throw(error(instantiation_error, _)).
  235spy(_:[]) :- !.
  236spy(M:[H|T]) :-
  237    !,
  238    spy(M:H),
  239    spy(M:T).
  240spy(Spec) :-
  241    notrace(prolog:debug_control_hook(spy(Spec))),
  242    !.
  243spy(Spec) :-
  244    '$find_predicate'(Spec, Preds),
  245    '$member'(PI, Preds),
  246        pi_to_head(PI, Head),
  247        '$define_predicate'(Head),
  248        '$spy'(Head),
  249    fail.
  250spy(_).
  251
  252nospy(_:X) :-
  253    var(X),
  254    throw(error(instantiation_error, _)).
  255nospy(_:[]) :- !.
  256nospy(M:[H|T]) :-
  257    !,
  258    nospy(M:H),
  259    nospy(M:T).
  260nospy(Spec) :-
  261    notrace(prolog:debug_control_hook(nospy(Spec))),
  262    !.
  263nospy(Spec) :-
  264    '$find_predicate'(Spec, Preds),
  265    '$member'(PI, Preds),
  266         pi_to_head(PI, Head),
  267        '$nospy'(Head),
  268    fail.
  269nospy(_).
  270
  271nospyall :-
  272    notrace(prolog:debug_control_hook(nospyall)),
  273    fail.
  274nospyall :-
  275    spy_point(Head),
  276        '$nospy'(Head),
  277    fail.
  278nospyall.
  279
  280pi_to_head(M:PI, M:Head) :-
  281    !,
  282    pi_to_head(PI, Head).
  283pi_to_head(Name/Arity, Head) :-
  284    functor(Head, Name, Arity).

debugging is det: Report current status of the debugger.

  290debugging :-
  291    notrace(prolog:debug_control_hook(debugging)),
  292    !.
  293debugging :-
  294    current_prolog_flag(debug, true),
  295    !,
  296    print_message(informational, debugging(on)),
  297    findall(H, spy_point(H), SpyPoints),
  298    print_message(informational, spying(SpyPoints)).
  299debugging :-
  300    print_message(informational, debugging(off)).
  301
  302spy_point(Module:Head) :-
  303    current_predicate(_, Module:Head),
  304    '$get_predicate_attribute'(Module:Head, spy, 1),
  305    \+ predicate_property(Module:Head, imported_from(_)).

flag(+Name, -Old, +New) is det: True when Old is the current value associated with the flag Name and New has become the new value.

  312flag(Name, Old, New) :-
  313    Old == New,
  314    !,
  315    get_flag(Name, Old).
  316flag(Name, Old, New) :-
  317    with_mutex('$flag', update_flag(Name, Old, New)).
  318
  319update_flag(Name, Old, New) :-
  320    get_flag(Name, Old),
  321    (   atom(New)
  322    ->  set_flag(Name, New)
  323    ;   Value is New,
  324        set_flag(Name, Value)
  325    ).
  326
  327
  328                /********************************
  329                *             ATOMS             *
  330                *********************************/
  331
  332dwim_match(A1, A2) :-
  333    dwim_match(A1, A2, _).
  334
  335atom_prefix(Atom, Prefix) :-
  336    sub_atom(Atom, 0, _, _, Prefix).
  337
  338
  339                /********************************
  340                *             SOURCE            *
  341                *********************************/

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.

  354source_file(File) :-
  355    (   current_prolog_flag(access_level, user)
  356    ->  Level = user
  357    ;   true
  358    ),
  359    (   ground(File)
  360    ->  (   '$time_source_file'(File, Time, Level)
  361        ;   absolute_file_name(File, Abs),
  362            '$time_source_file'(Abs, Time, Level)
  363        ), !
  364    ;   '$time_source_file'(File, Time, Level)
  365    ),
  366    Time > 0.0.

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

  373:- meta_predicate source_file(:, ?).  374
  375source_file(M:Head, File) :-
  376    nonvar(M), nonvar(Head),
  377    !,
  378    (   '$c_current_predicate'(_, M:Head),
  379        predicate_property(M:Head, multifile)
  380    ->  multi_source_files(M:Head, Files),
  381        '$member'(File, Files)
  382    ;   '$source_file'(M:Head, File)
  383    ).
  384source_file(M:Head, File) :-
  385    (   nonvar(File)
  386    ->  true
  387    ;   source_file(File)
  388    ),
  389    '$source_file_predicates'(File, Predicates),
  390    '$member'(M:Head, Predicates).
  391
  392:- thread_local found_src_file/1.  393
  394multi_source_files(Head, Files) :-
  395    call_cleanup(
  396        findall(File, multi_source_file(Head, File), Files),
  397        retractall(found_src_file(_))).
  398
  399multi_source_file(Head, File) :-
  400    nth_clause(Head, _, Clause),
  401    clause_property(Clause, source(File)),
  402    \+ found_src_file(File),
  403    asserta(found_src_file(File)).

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

  410source_file_property(File, P) :-
  411    nonvar(File),
  412    !,
  413    canonical_source_file(File, Path),
  414    property_source_file(P, Path).
  415source_file_property(File, P) :-
  416    property_source_file(P, File).
  417
  418property_source_file(modified(Time), File) :-
  419    '$time_source_file'(File, Time, user).
  420property_source_file(source(Source), File) :-
  421    (   '$source_file_property'(File, from_state, true)
  422    ->  Source = state
  423    ;   '$source_file_property'(File, resource, true)
  424    ->  Source = resource
  425    ;   Source = file
  426    ).
  427property_source_file(module(M), File) :-
  428    (   nonvar(M)
  429    ->  '$current_module'(M, File)
  430    ;   nonvar(File)
  431    ->  '$current_module'(ML, File),
  432        (   atom(ML)
  433        ->  M = ML
  434        ;   '$member'(M, ML)
  435        )
  436    ;   '$current_module'(M, File)
  437    ).
  438property_source_file(load_context(Module, Location, Options), File) :-
  439    '$time_source_file'(File, _, user),
  440    clause(system:'$load_context_module'(File, Module, Options), true, Ref),
  441    (   clause_property(Ref, file(FromFile)),
  442        clause_property(Ref, line_count(FromLine))
  443    ->  Location = FromFile:FromLine
  444    ;   Location = user
  445    ).
  446property_source_file(includes(Master, Stamp), File) :-
  447    system:'$included'(File, _Line, Master, Stamp).
  448property_source_file(included_in(Master, Line), File) :-
  449    system:'$included'(Master, Line, File, _).
  450property_source_file(derived_from(DerivedFrom, Stamp), File) :-
  451    system:'$derived_source'(File, DerivedFrom, Stamp).
  452property_source_file(reloading, File) :-
  453    source_file(File),
  454    '$source_file_property'(File, reloading, true).
  455property_source_file(load_count(Count), File) :-
  456    source_file(File),
  457    '$source_file_property'(File, load_count, Count).
  458property_source_file(number_of_clauses(Count), File) :-
  459    source_file(File),
  460    '$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.

  467canonical_source_file(Spec, File) :-
  468    atom(Spec),
  469    '$time_source_file'(Spec, _, _),
  470    !,
  471    File = Spec.
  472canonical_source_file(Spec, File) :-
  473    system:'$included'(_Master, _Line, Spec, _),
  474    !,
  475    File = Spec.
  476canonical_source_file(Spec, File) :-
  477    absolute_file_name(Spec,
  478                           [ file_type(prolog),
  479                             access(read),
  480                             file_errors(fail)
  481                           ],
  482                           File),
  483    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.

  500exists_source(Source) :-
  501    exists_source(Source, _Path).
  502
  503exists_source(Source, Path) :-
  504    absolute_file_name(Source, Path,
  505                       [ file_type(prolog),
  506                         access(read),
  507                         file_errors(fail)
  508                       ]).

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.

  517prolog_load_context(module, Module) :-
  518    '$current_source_module'(Module).
  519prolog_load_context(file, File) :-
  520    input_file(File).
  521prolog_load_context(source, F) :-       % SICStus compatibility
  522    input_file(F0),
  523    '$input_context'(Context),
  524    '$top_file'(Context, F0, F).
  525prolog_load_context(stream, S) :-
  526    (   system:'$load_input'(_, S0)
  527    ->  S = S0
  528    ).
  529prolog_load_context(directory, D) :-
  530    input_file(F),
  531    file_directory_name(F, D).
  532prolog_load_context(dialect, D) :-
  533    current_prolog_flag(emulated_dialect, D).
  534prolog_load_context(term_position, TermPos) :-
  535    source_location(_, L),
  536    (   nb_current('$term_position', Pos),
  537        compound(Pos),              % actually set
  538        stream_position_data(line_count, Pos, L)
  539    ->  TermPos = Pos
  540    ;   TermPos = '$stream_position'(0,L,0,0)
  541    ).
  542prolog_load_context(script, Bool) :-
  543    (   '$toplevel':loaded_init_file(script, Path),
  544        input_file(File),
  545        same_file(File, Path)
  546    ->  Bool = true
  547    ;   Bool = false
  548    ).
  549prolog_load_context(variable_names, Bindings) :-
  550    nb_current('$variable_names', Bindings).
  551prolog_load_context(term, Term) :-
  552    nb_current('$term', Term).
  553prolog_load_context(reloading, true) :-
  554    prolog_load_context(source, F),
  555    '$source_file_property'(F, reloading, true).
  556
  557input_file(File) :-
  558    (   system:'$load_input'(_, Stream)
  559    ->  stream_property(Stream, file_name(File))
  560    ),
  561    !.
  562input_file(File) :-
  563    source_location(File, _).

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

  570:- dynamic system:'$resolved_source_path'/2.  571
  572unload_file(File) :-
  573    (   canonical_source_file(File, Path)
  574    ->  '$unload_file'(Path),
  575        retractall(system:'$resolved_source_path'(_, Path))
  576    ;   true
  577    ).
  578
  579		 /*******************************
  580		 *      FOREIGN LIBRARIES	*
  581		 *******************************/

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.

  600use_foreign_library(FileSpec) :-
  601    ensure_shlib,
  602    initialization(shlib:load_foreign_library(FileSpec), now).
  603
  604use_foreign_library(FileSpec, Entry) :-
  605    ensure_shlib,
  606    initialization(shlib:load_foreign_library(FileSpec, Entry), now).
  607
  608ensure_shlib :-
  609    '$get_predicate_attribute'(shlib:load_foreign_library(_), defined, 1),
  610    '$get_predicate_attribute'(shlib:load_foreign_library(_,_), defined, 1),
  611    !.
  612ensure_shlib :-
  613    use_module(library(shlib), []).
  614
  615
  616                 /*******************************
  617                 *            STREAMS           *
  618                 *******************************/

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

  625stream_position_data(Prop, Term, Value) :-
  626    nonvar(Prop),
  627    !,
  628    (   stream_position_field(Prop, Pos)
  629    ->  arg(Pos, Term, Value)
  630    ;   throw(error(domain_error(stream_position_data, Prop)))
  631    ).
  632stream_position_data(Prop, Term, Value) :-
  633    stream_position_field(Prop, Pos),
  634    arg(Pos, Term, Value).
  635
  636stream_position_field(char_count,    1).
  637stream_position_field(line_count,    2).
  638stream_position_field(line_position, 3).
  639stream_position_field(byte_count,    4).
  640
  641
  642                 /*******************************
  643                 *            CONTROL           *
  644                 *******************************/

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.

  652:- meta_predicate
  653    call_with_depth_limit(0, +, -).  654
  655call_with_depth_limit(G, Limit, Result) :-
  656    '$depth_limit'(Limit, OLimit, OReached),
  657    (   catch(G, E, '$depth_limit_except'(OLimit, OReached, E)),
  658        '$depth_limit_true'(Limit, OLimit, OReached, Result, Det),
  659        ( Det == ! -> ! ; true )
  660    ;   '$depth_limit_false'(OLimit, OReached, Result)
  661    ).

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.

  674:- meta_predicate
  675    call_with_inference_limit(0, +, -).  676
  677call_with_inference_limit(G, Limit, Result) :-
  678    '$inference_limit'(Limit, OLimit),
  679    (   catch(G, Except,
  680              system:'$inference_limit_except'(OLimit, Except, Result0)),
  681        (   Result0 == inference_limit_exceeded
  682        ->  !
  683        ;   system:'$inference_limit_true'(Limit, OLimit, Result0),
  684            ( Result0 == ! -> ! ; true )
  685        ),
  686        Result = Result0
  687    ;   system:'$inference_limit_false'(OLimit)
  688    ).
  689
  690
  691                /********************************
  692                *           DATA BASE           *
  693                *********************************/
  694
  695/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  696The predicate current_predicate/2 is   a  difficult subject since  the
  697introduction  of defaulting     modules   and   dynamic     libraries.
  698current_predicate/2 is normally  called with instantiated arguments to
  699verify some  predicate can   be called without trapping   an undefined
  700predicate.  In this case we must  perform the search algorithm used by
  701the prolog system itself.
  702
  703If the pattern is not fully specified, we only generate the predicates
  704actually available in this  module.   This seems the best for listing,
  705etc.
  706- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  707
  708
  709:- meta_predicate
  710    current_predicate(?, :),
  711    '$defined_predicate'(:).  712
  713current_predicate(Name, Module:Head) :-
  714    (var(Module) ; var(Head)),
  715    !,
  716    generate_current_predicate(Name, Module, Head).
  717current_predicate(Name, Term) :-
  718    '$c_current_predicate'(Name, Term),
  719    '$defined_predicate'(Term),
  720    !.
  721current_predicate(Name, Module:Head) :-
  722    default_module(Module, DefModule),
  723    '$c_current_predicate'(Name, DefModule:Head),
  724    '$defined_predicate'(DefModule:Head),
  725    !.
  726current_predicate(Name, Module:Head) :-
  727    '$autoload':autoload_in(Module, general),
  728    \+ current_prolog_flag(Module:unknown, fail),
  729    (   compound(Head)
  730    ->  compound_name_arity(Head, Name, Arity)
  731    ;   Name = Head, Arity = 0
  732    ),
  733    '$find_library'(Module, Name, Arity, _LoadModule, _Library),
  734    !.
  735
  736generate_current_predicate(Name, Module, Head) :-
  737    current_module(Module),
  738    QHead = Module:Head,
  739    '$c_current_predicate'(Name, QHead),
  740    '$get_predicate_attribute'(QHead, defined, 1).
  741
  742'$defined_predicate'(Head) :-
  743    '$get_predicate_attribute'(Head, defined, 1),
  744    !.

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

  750:- meta_predicate
  751    predicate_property(:, ?).  752
  753:- multifile
  754    '$predicate_property'/2.  755
  756:- '$iso'(predicate_property/2).  757
  758predicate_property(Pred, Property) :-           % Mode ?,+
  759    nonvar(Property),
  760    !,
  761    property_predicate(Property, Pred).
  762predicate_property(Pred, Property) :-           % Mode +,-
  763    define_or_generate(Pred),
  764    '$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.

  772property_predicate(undefined, Pred) :-
  773    !,
  774    Pred = Module:Head,
  775    current_module(Module),
  776    '$c_current_predicate'(_, Pred),
  777    \+ '$defined_predicate'(Pred),          % Speed up a bit
  778    \+ current_predicate(_, Pred),
  779    goal_name_arity(Head, Name, Arity),
  780    \+ system_undefined(Module:Name/Arity).
  781property_predicate(visible, Pred) :-
  782    !,
  783    visible_predicate(Pred).
  784property_predicate(autoload(File), Head) :-
  785    !,
  786    \+ current_prolog_flag(autoload, false),
  787    '$autoload':autoloadable(Head, File).
  788property_predicate(implementation_module(IM), M:Head) :-
  789    !,
  790    atom(M),
  791    (   default_module(M, DM),
  792        '$get_predicate_attribute'(DM:Head, defined, 1)
  793    ->  (   '$get_predicate_attribute'(DM:Head, imported, ImportM)
  794        ->  IM = ImportM
  795        ;   IM = M
  796        )
  797    ;   \+ current_prolog_flag(M:unknown, fail),
  798        goal_name_arity(Head, Name, Arity),
  799        '$find_library'(_, Name, Arity, LoadModule, _File)
  800    ->  IM = LoadModule
  801    ;   M = IM
  802    ).
  803property_predicate(iso, _:Head) :-
  804    callable(Head),
  805    !,
  806    goal_name_arity(Head, Name, Arity),
  807    current_predicate(system:Name/Arity),
  808    '$predicate_property'(iso, system:Head).
  809property_predicate(built_in, Module:Head) :-
  810    callable(Head),
  811    !,
  812    goal_name_arity(Head, Name, Arity),
  813    current_predicate(Module:Name/Arity),
  814    '$predicate_property'(built_in, Module:Head).
  815property_predicate(Property, Pred) :-
  816    define_or_generate(Pred),
  817    '$predicate_property'(Property, Pred).
  818
  819goal_name_arity(Head, Name, Arity) :-
  820    compound(Head),
  821    !,
  822    compound_name_arity(Head, Name, Arity).
  823goal_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.

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

  952visible_predicate(Pred) :-
  953    Pred = M:Head,
  954    current_module(M),
  955    (   callable(Head)
  956    ->  (   '$get_predicate_attribute'(Pred, defined, 1)
  957        ->  true
  958        ;   \+ current_prolog_flag(M:unknown, fail),
  959            functor(Head, Name, Arity),
  960            '$find_library'(M, Name, Arity, _LoadModule, _Library)
  961        )
  962    ;   setof(PI, visible_in_module(M, PI), PIs),
  963        '$member'(Name/Arity, PIs),
  964        functor(Head, Name, Arity)
  965    ).
  966
  967visible_in_module(M, Name/Arity) :-
  968    default_module(M, DefM),
  969    DefHead = DefM:Head,
  970    '$c_current_predicate'(_, DefHead),
  971    '$get_predicate_attribute'(DefHead, defined, 1),
  972    \+ hidden_system_predicate(Head),
  973    functor(Head, Name, Arity).
  974visible_in_module(_, Name/Arity) :-
  975    '$in_library'(Name, Arity, _).
  976
  977hidden_system_predicate(Head) :-
  978    functor(Head, Name, _),
  979    atom(Name),                     % Avoid [].
  980    sub_atom(Name, 0, _, _, $),
  981    \+ 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.

 1006clause_property(Clause, Property) :-
 1007    '$clause_property'(Property, Clause).
 1008
 1009'$clause_property'(line_count(LineNumber), Clause) :-
 1010    '$get_clause_attribute'(Clause, line_count, LineNumber).
 1011'$clause_property'(file(File), Clause) :-
 1012    '$get_clause_attribute'(Clause, file, File).
 1013'$clause_property'(source(File), Clause) :-
 1014    '$get_clause_attribute'(Clause, owner, File).
 1015'$clause_property'(size(Bytes), Clause) :-
 1016    '$get_clause_attribute'(Clause, size, Bytes).
 1017'$clause_property'(fact, Clause) :-
 1018    '$get_clause_attribute'(Clause, fact, true).
 1019'$clause_property'(erased, Clause) :-
 1020    '$get_clause_attribute'(Clause, erased, true).
 1021'$clause_property'(predicate(PI), Clause) :-
 1022    '$get_clause_attribute'(Clause, predicate_indicator, PI).
 1023'$clause_property'(module(M), Clause) :-
 1024    '$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)

 1038dynamic(M:Predicates, Options) :-
 1039    '$must_be'(list, Predicates),
 1040    options_properties(Options, Props),
 1041    set_pprops(Predicates, M, [dynamic|Props]).
 1042
 1043set_pprops([], _, _).
 1044set_pprops([H|T], M, Props) :-
 1045    set_pprops1(Props, M:H),
 1046    strip_module(M:H, M2, P),
 1047    '$pi_head'(M2:P, Pred),
 1048    '$set_table_wrappers'(Pred),
 1049    set_pprops(T, M, Props).
 1050
 1051set_pprops1([], _).
 1052set_pprops1([H|T], P) :-
 1053    (   atom(H)
 1054    ->  '$set_predicate_attribute'(P, H, true)
 1055    ;   H =.. [Name,Value]
 1056    ->  '$set_predicate_attribute'(P, Name, Value)
 1057    ),
 1058    set_pprops1(T, P).
 1059
 1060options_properties(Options, Props) :-
 1061    G = opt_prop(_,_,_,_),
 1062    findall(G, G, Spec),
 1063    options_properties(Spec, Options, Props).
 1064
 1065options_properties([], _, []).
 1066options_properties([opt_prop(Name, Type, SetValue, Prop)|T],
 1067                   Options, [Prop|PT]) :-
 1068    Opt =.. [Name,V],
 1069    '$option'(Opt, Options),
 1070    '$must_be'(Type, V),
 1071    V = SetValue,
 1072    !,
 1073    options_properties(T, Options, PT).
 1074options_properties([_|T], Options, PT) :-
 1075    options_properties(T, Options, PT).
 1076
 1077opt_prop(incremental,   boolean,               Bool,  incremental(Bool)).
 1078opt_prop(abstract,      between(0,0),          0,     abstract).
 1079opt_prop(multifile,     boolean,               true,  multifile).
 1080opt_prop(discontiguous, boolean,               true,  discontiguous).
 1081opt_prop(volatile,      boolean,               true,  volatile).
 1082opt_prop(thread,        oneof(atom, [local,shared],[local,shared]),
 1083                                               local, thread_local).
 1084
 1085                /********************************
 1086                *            MODULES            *
 1087                *********************************/

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

 1093current_module(Module) :-
 1094    '$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.

 1110module_property(Module, Property) :-
 1111    nonvar(Module), nonvar(Property),
 1112    !,
 1113    property_module(Property, Module).
 1114module_property(Module, Property) :-    % -, file(File)
 1115    nonvar(Property), Property = file(File),
 1116    !,
 1117    (   nonvar(File)
 1118    ->  '$current_module'(Modules, File),
 1119        (   atom(Modules)
 1120        ->  Module = Modules
 1121        ;   '$member'(Module, Modules)
 1122        )
 1123    ;   '$current_module'(Module, File),
 1124        File \== []
 1125    ).
 1126module_property(Module, Property) :-
 1127    current_module(Module),
 1128    property_module(Property, Module).
 1129
 1130property_module(Property, Module) :-
 1131    module_property(Property),
 1132    (   Property = exported_operators(List)
 1133    ->  '$exported_ops'(Module, List, [])
 1134    ;   '$module_property'(Module, Property)
 1135    ).
 1136
 1137module_property(class(_)).
 1138module_property(file(_)).
 1139module_property(line_count(_)).
 1140module_property(exports(_)).
 1141module_property(exported_operators(_)).
 1142module_property(size(_)).
 1143module_property(program_size(_)).
 1144module_property(program_space(_)).
 1145module_property(last_modified_generation(_)).

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

 1151module(Module) :-
 1152    atom(Module),
 1153    current_module(Module),
 1154    !,
 1155    '$set_typein_module'(Module).
 1156module(Module) :-
 1157    '$set_typein_module'(Module),
 1158    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.

 1165working_directory(Old, New) :-
 1166    '$cwd'(Old),
 1167    (   Old == New
 1168    ->  true
 1169    ;   '$chdir'(New)
 1170    ).
 1171
 1172
 1173                 /*******************************
 1174                 *            TRIES             *
 1175                 *******************************/

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

 1181current_trie(Trie) :-
 1182    current_blob(Trie, trie),
 1183    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

 1219trie_property(Trie, Property) :-
 1220    current_trie(Trie),
 1221    trie_property(Property),
 1222    '$trie_property'(Trie, Property).
 1223
 1224trie_property(node_count(_)).
 1225trie_property(value_count(_)).
 1226trie_property(size(_)).
 1227trie_property(hashed(_)).
 1228trie_property(compiled_size(_)).
 1229                                                % below only when -DO_TRIE_STATS
 1230trie_property(lookup_count(_)).                 % is enabled in pl-trie.h
 1231trie_property(gen_call_count(_)).
 1232trie_property(invalidated(_)).                  % IDG stats
 1233trie_property(reevaluated(_)).
 1234trie_property(deadlock(_)).                     % Shared tabling stats
 1235trie_property(wait(_)).
 1236trie_property(idg_affected_count(_)).
 1237trie_property(idg_dependent_count(_)).
 1238trie_property(idg_size(_)).
 1239
 1240
 1241                /********************************
 1242                *      SYSTEM INTERACTION       *
 1243                *********************************/
 1244
 1245shell(Command) :-
 1246    shell(Command, 0).
 1247
 1248
 1249                 /*******************************
 1250                 *            SIGNALS           *
 1251                 *******************************/
 1252
 1253:- meta_predicate
 1254    on_signal(+, :, :),
 1255    current_signal(?, ?, :).

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

 1259on_signal(Signal, Old, New) :-
 1260    atom(Signal),
 1261    !,
 1262    '$on_signal'(_Num, Signal, Old, New).
 1263on_signal(Signal, Old, New) :-
 1264    integer(Signal),
 1265    !,
 1266    '$on_signal'(Signal, _Name, Old, New).
 1267on_signal(Signal, _Old, _New) :-
 1268    '$type_error'(signal_name, Signal).

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

 1272current_signal(Name, Id, Handler) :-
 1273    between(1, 32, Id),
 1274    '$on_signal'(Id, Name, Handler, Handler).
 1275
 1276:- multifile
 1277    prolog:called_by/2. 1278
 1279prolog:called_by(on_signal(_,_,New), [New+1]) :-
 1280    (   new == throw
 1281    ;   new == default
 1282    ), !, fail.
 1283
 1284
 1285                 /*******************************
 1286                 *            DLOPEN            *
 1287                 *******************************/

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.

 1301open_shared_object(File, Handle) :-
 1302    open_shared_object(File, Handle, []). % use pl-load.c defaults
 1303
 1304open_shared_object(File, Handle, Flags) :-
 1305    (   is_list(Flags)
 1306    ->  true
 1307    ;   throw(error(type_error(list, Flags), _))
 1308    ),
 1309    map_dlflags(Flags, Mask),
 1310    '$open_shared_object'(File, Handle, Mask).
 1311
 1312dlopen_flag(now,        2'01).          % see pl-load.c for these constants
 1313dlopen_flag(global,     2'10).          % Solaris only
 1314
 1315map_dlflags([], 0).
 1316map_dlflags([F|T], M) :-
 1317    map_dlflags(T, M0),
 1318    (   dlopen_flag(F, I)
 1319    ->  true
 1320    ;   throw(error(domain_error(dlopen_flag, F), _))
 1321    ),
 1322    M is M0 \/ I.
 1323
 1324
 1325                 /*******************************
 1326                 *             I/O              *
 1327                 *******************************/
 1328
 1329format(Fmt) :-
 1330    format(Fmt, []).
 1331
 1332                 /*******************************
 1333                 *            FILES             *
 1334                 *******************************/

absolute_file_name(+Term, -AbsoluteFile)

 1338absolute_file_name(Name, Abs) :-
 1339    atomic(Name),
 1340    !,
 1341    '$absolute_file_name'(Name, Abs).
 1342absolute_file_name(Term, Abs) :-
 1343    '$chk_file'(Term, [''], [access(read)], true, File),
 1344    !,
 1345    '$absolute_file_name'(File, Abs).
 1346absolute_file_name(Term, Abs) :-
 1347    '$chk_file'(Term, [''], [], true, File),
 1348    !,
 1349    '$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.

 1357tmp_file_stream(Enc, File, Stream) :-
 1358    atom(Enc), var(File), var(Stream),
 1359    !,
 1360    '$tmp_file_stream'('', Enc, File, Stream).
 1361tmp_file_stream(File, Stream, Options) :-
 1362    current_prolog_flag(encoding, DefEnc),
 1363    '$option'(encoding(Enc), Options, DefEnc),
 1364    '$option'(extension(Ext), Options, ''),
 1365    '$tmp_file_stream'(Ext, Enc, File, Stream),
 1366    set_stream(Stream, file_name(File)).
 1367
 1368
 1369                /********************************
 1370                *        MEMORY MANAGEMENT      *
 1371                *********************************/

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.

 1380garbage_collect :-
 1381    '$garbage_collect'(0).

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

 1387set_prolog_stack(Stack, Option) :-
 1388    Option =.. [Name,Value0],
 1389    Value is Value0,
 1390    '$set_prolog_stack'(Stack, Name, _Old, Value).

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

 1396prolog_stack_property(Stack, Property) :-
 1397    stack_property(P),
 1398    stack_name(Stack),
 1399    Property =.. [P,Value],
 1400    '$set_prolog_stack'(Stack, P, Value, Value).
 1401
 1402stack_name(local).
 1403stack_name(global).
 1404stack_name(trail).
 1405
 1406stack_property(limit).
 1407stack_property(spare).
 1408stack_property(min_free).
 1409stack_property(low).
 1410stack_property(factor).
 1411
 1412
 1413                 /*******************************
 1414                 *             TERM             *
 1415                 *******************************/
 1416
 1417:- '$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.

 1425numbervars(Term, From, To) :-
 1426    numbervars(Term, From, To, []).
 1427
 1428
 1429                 /*******************************
 1430                 *            STRING            *
 1431                 *******************************/

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

 1437term_string(Term, String, Options) :-
 1438    nonvar(String),
 1439    !,
 1440    read_term_from_atom(String, Term, Options).
 1441term_string(Term, String, Options) :-
 1442    (   '$option'(quoted(_), Options)
 1443    ->  Options1 = Options
 1444    ;   '$merge_options'(_{quoted:true}, Options, Options1)
 1445    ),
 1446    format(string(String), '~W', [Term, Options1]).
 1447
 1448
 1449                 /*******************************
 1450                 *             GVAR             *
 1451                 *******************************/

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

 1457nb_setval(Name, Value) :-
 1458    duplicate_term(Value, Copy),
 1459    nb_linkval(Name, Copy).
 1460
 1461
 1462		 /*******************************
 1463		 *            THREADS		*
 1464		 *******************************/
 1465
 1466:- meta_predicate
 1467    thread_create(0, -).

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

 1473thread_create(Goal, Id) :-
 1474    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.

 1483thread_join(Id) :-
 1484    thread_join(Id, Status),
 1485    (   Status == true
 1486    ->  true
 1487    ;   throw(error(thread_error(Id, Status), _))
 1488    ).

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.

 1505set_prolog_gc_thread(Status) :-
 1506    var(Status),
 1507    !,
 1508    '$instantiation_error'(Status).
 1509set_prolog_gc_thread(false) :-
 1510    !,
 1511    set_prolog_flag(gc_thread, false),
 1512    (   current_prolog_flag(threads, true)
 1513    ->  (   '$gc_stop'
 1514        ->  thread_join(gc)
 1515        ;   true
 1516        )
 1517    ;   true
 1518    ).
 1519set_prolog_gc_thread(true) :-
 1520    !,
 1521    set_prolog_flag(gc_thread, true).
 1522set_prolog_gc_thread(stop) :-
 1523    !,
 1524    (   current_prolog_flag(threads, true)
 1525    ->  (   '$gc_stop'
 1526        ->  thread_join(gc)
 1527        ;   true
 1528        )
 1529    ;   true
 1530    ).
 1531set_prolog_gc_thread(Status) :-
 1532    '$domain_error'(gc_thread, Status).

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

 1541transaction(Goal) :-
 1542    '$transaction'(Goal, []).
 1543transaction(Goal, Options) :-
 1544    '$transaction'(Goal, Options).
 1545transaction(Goal, Constraint, Mutex) :-
 1546    '$transaction'(Goal, Constraint, Mutex).
 1547snapshot(Goal) :-
 1548    '$snapshot'(Goal).

$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.

 1556:- meta_predicate
 1557    '$wrap_predicate'(:, +, -, -, +). 1558
 1559'$wrap_predicate'(M:Head, WName, Closure, call(Wrapped), Body) :-
 1560    callable_name_arguments(Head, PName, Args),
 1561    callable_name_arity(Head, PName, Arity),
 1562    (   is_most_general_term(Head)
 1563    ->  true
 1564    ;   '$domain_error'(most_general_term, Head)
 1565    ),
 1566    atomic_list_concat(['$wrap$', PName], WrapName),
 1567    volatile(M:WrapName/Arity),
 1568    module_transparent(M:WrapName/Arity),
 1569    WHead =.. [WrapName|Args],
 1570    '$c_wrap_predicate'(M:Head, WName, Closure, Wrapped, M:(WHead :- Body)).
 1571
 1572callable_name_arguments(Head, PName, Args) :-
 1573    atom(Head),
 1574    !,
 1575    PName = Head,
 1576    Args = [].
 1577callable_name_arguments(Head, PName, Args) :-
 1578    compound_name_arguments(Head, PName, Args).
 1579
 1580callable_name_arity(Head, PName, Arity) :-
 1581    atom(Head),
 1582    !,
 1583    PName = Head,
 1584    Arity = 0.
 1585callable_name_arity(Head, PName, Arity) :-
 1586    compound_name_arity(Head, PName, Arity)