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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/*
   39Consult, derivates and basic things.   This  module  is  loaded  by  the
   40C-written  bootstrap  compiler.
   41
   42The $:- directive  is  executed  by  the  bootstrap  compiler,  but  not
   43inserted  in  the  intermediate  code  file.   Used  to print diagnostic
   44messages and start the Prolog defined compiler for  the  remaining  boot
   45modules.
   46
   47If you want  to  debug  this  module,  put  a  '$:-'(trace).   directive
   48somewhere.   The  tracer will work properly under boot compilation as it
   49will use the C defined write predicate  to  print  goals  and  does  not
   50attempt to call the Prolog defined trace interceptor.
   51*/
   52
   53		/********************************
   54		*    LOAD INTO MODULE SYSTEM    *
   55		********************************/
   56
   57:- '$set_source_module'(system).   58
   59'$boot_message'(_Format, _Args) :-
   60    current_prolog_flag(verbose, silent),
   61    !.
   62'$boot_message'(Format, Args) :-
   63    format(Format, Args),
   64    !.
   65
   66'$:-'('$boot_message'('Loading boot file ...~n', [])).
 memberchk(?E, ?List) is semidet
Semantically equivalent to once(member(E,List)). Implemented in C. If List is partial though we need to do the work in Prolog to get the proper constraint behavior. Needs to be defined early as the boot code uses it.
   76memberchk(E, List) :-
   77    '$memberchk'(E, List, Tail),
   78    (   nonvar(Tail)
   79    ->  true
   80    ;   Tail = [_|_],
   81	memberchk(E, Tail)
   82    ).
   83
   84		/********************************
   85		*          DIRECTIVES           *
   86		*********************************/
   87
   88:- meta_predicate
   89    dynamic(:),
   90    multifile(:),
   91    public(:),
   92    module_transparent(:),
   93    discontiguous(:),
   94    volatile(:),
   95    thread_local(:),
   96    noprofile(:),
   97    non_terminal(:),
   98    det(:),
   99    '$clausable'(:),
  100    '$iso'(:),
  101    '$hide'(:).
 dynamic +Spec is det
 multifile +Spec is det
 module_transparent +Spec is det
 discontiguous +Spec is det
 volatile +Spec is det
 thread_local +Spec is det
 noprofile(+Spec) is det
 public +Spec is det
 non_terminal(+Spec) is det
Predicate versions of standard directives that set predicate attributes. These predicates bail out with an error on the first failure (typically permission errors).
 $iso(+Spec) is det
Set the ISO flag. This defines that the predicate cannot be redefined inside a module.
 $clausable(+Spec) is det
Specify that we can run clause/2 on a predicate, even if it is static. ISO specifies that public also plays this role. in SWI, public means that the predicate can be called, even if we cannot find a reference to it.
 $hide(+Spec) is det
Specify that the predicate cannot be seen in the debugger.
  133dynamic(Spec)            :- '$set_pattr'(Spec, pred, dynamic(true)).
  134multifile(Spec)          :- '$set_pattr'(Spec, pred, multifile(true)).
  135module_transparent(Spec) :- '$set_pattr'(Spec, pred, transparent(true)).
  136discontiguous(Spec)      :- '$set_pattr'(Spec, pred, discontiguous(true)).
  137volatile(Spec)           :- '$set_pattr'(Spec, pred, volatile(true)).
  138thread_local(Spec)       :- '$set_pattr'(Spec, pred, thread_local(true)).
  139noprofile(Spec)          :- '$set_pattr'(Spec, pred, noprofile(true)).
  140public(Spec)             :- '$set_pattr'(Spec, pred, public(true)).
  141non_terminal(Spec)       :- '$set_pattr'(Spec, pred, non_terminal(true)).
  142det(Spec)                :- '$set_pattr'(Spec, pred, det(true)).
  143'$iso'(Spec)             :- '$set_pattr'(Spec, pred, iso(true)).
  144'$clausable'(Spec)       :- '$set_pattr'(Spec, pred, clausable(true)).
  145'$hide'(Spec)            :- '$set_pattr'(Spec, pred, trace(false)).
  146
  147'$set_pattr'(M:Pred, How, Attr) :-
  148    '$set_pattr'(Pred, M, How, Attr).
 $set_pattr(+Spec, +Module, +From, +Attr)
Set predicate attributes. From is one of pred or directive.
  154'$set_pattr'(X, _, _, _) :-
  155    var(X),
  156    '$uninstantiation_error'(X).
  157'$set_pattr'(as(Spec,Options), M, How, Attr0) :-
  158    !,
  159    '$attr_options'(Options, Attr0, Attr),
  160    '$set_pattr'(Spec, M, How, Attr).
  161'$set_pattr'([], _, _, _) :- !.
  162'$set_pattr'([H|T], M, How, Attr) :-           % ISO
  163    !,
  164    '$set_pattr'(H, M, How, Attr),
  165    '$set_pattr'(T, M, How, Attr).
  166'$set_pattr'((A,B), M, How, Attr) :-           % ISO and traditional
  167    !,
  168    '$set_pattr'(A, M, How, Attr),
  169    '$set_pattr'(B, M, How, Attr).
  170'$set_pattr'(M:T, _, How, Attr) :-
  171    !,
  172    '$set_pattr'(T, M, How, Attr).
  173'$set_pattr'(PI, M, _, []) :-
  174    !,
  175    '$pi_head'(M:PI, Pred),
  176    '$set_table_wrappers'(Pred).
  177'$set_pattr'(A, M, How, [O|OT]) :-
  178    !,
  179    '$set_pattr'(A, M, How, O),
  180    '$set_pattr'(A, M, How, OT).
  181'$set_pattr'(A, M, pred, Attr) :-
  182    !,
  183    Attr =.. [Name,Val],
  184    '$set_pi_attr'(M:A, Name, Val).
  185'$set_pattr'(A, M, directive, Attr) :-
  186    !,
  187    Attr =.. [Name,Val],
  188    catch('$set_pi_attr'(M:A, Name, Val),
  189	  error(E, _),
  190	  print_message(error, error(E, context((Name)/1,_)))).
  191
  192'$set_pi_attr'(PI, Name, Val) :-
  193    '$pi_head'(PI, Head),
  194    '$set_predicate_attribute'(Head, Name, Val).
  195
  196'$attr_options'(Var, _, _) :-
  197    var(Var),
  198    !,
  199    '$uninstantiation_error'(Var).
  200'$attr_options'((A,B), Attr0, Attr) :-
  201    !,
  202    '$attr_options'(A, Attr0, Attr1),
  203    '$attr_options'(B, Attr1, Attr).
  204'$attr_options'(Opt, Attr0, Attrs) :-
  205    '$must_be'(ground, Opt),
  206    (   '$attr_option'(Opt, AttrX)
  207    ->  (   is_list(Attr0)
  208	->  '$join_attrs'(AttrX, Attr0, Attrs)
  209	;   '$join_attrs'(AttrX, [Attr0], Attrs)
  210	)
  211    ;   '$domain_error'(predicate_option, Opt)
  212    ).
  213
  214'$join_attrs'([], Attrs, Attrs) :-
  215    !.
  216'$join_attrs'([H|T], Attrs0, Attrs) :-
  217    !,
  218    '$join_attrs'(H, Attrs0, Attrs1),
  219    '$join_attrs'(T, Attrs1, Attrs).
  220'$join_attrs'(Attr, Attrs, Attrs) :-
  221    memberchk(Attr, Attrs),
  222    !.
  223'$join_attrs'(Attr, Attrs, Attrs) :-
  224    Attr =.. [Name,Value],
  225    Gen =.. [Name,Existing],
  226    memberchk(Gen, Attrs),
  227    !,
  228    throw(error(conflict_error(Name, Value, Existing), _)).
  229'$join_attrs'(Attr, Attrs0, Attrs) :-
  230    '$append'(Attrs0, [Attr], Attrs).
  231
  232'$attr_option'(incremental, [incremental(true),opaque(false)]).
  233'$attr_option'(monotonic, monotonic(true)).
  234'$attr_option'(lazy, lazy(true)).
  235'$attr_option'(opaque, [incremental(false),opaque(true)]).
  236'$attr_option'(abstract(Level0), abstract(Level)) :-
  237    '$table_option'(Level0, Level).
  238'$attr_option'(subgoal_abstract(Level0), subgoal_abstract(Level)) :-
  239    '$table_option'(Level0, Level).
  240'$attr_option'(answer_abstract(Level0), answer_abstract(Level)) :-
  241    '$table_option'(Level0, Level).
  242'$attr_option'(max_answers(Level0), max_answers(Level)) :-
  243    '$table_option'(Level0, Level).
  244'$attr_option'(volatile, volatile(true)).
  245'$attr_option'(multifile, multifile(true)).
  246'$attr_option'(discontiguous, discontiguous(true)).
  247'$attr_option'(shared, thread_local(false)).
  248'$attr_option'(local, thread_local(true)).
  249'$attr_option'(private, thread_local(true)).
  250
  251'$table_option'(Value0, _Value) :-
  252    var(Value0),
  253    !,
  254    '$instantiation_error'(Value0).
  255'$table_option'(Value0, Value) :-
  256    integer(Value0),
  257    Value0 >= 0,
  258    !,
  259    Value = Value0.
  260'$table_option'(off, -1) :-
  261    !.
  262'$table_option'(false, -1) :-
  263    !.
  264'$table_option'(infinite, -1) :-
  265    !.
  266'$table_option'(Value, _) :-
  267    '$domain_error'(nonneg_or_false, Value).
 $pattr_directive(+Spec, +Module) is det
This implements the directive version of dynamic/1, multifile/1, etc. This version catches and prints errors. If the directive specifies multiple predicates, processing after an error continues with the remaining predicates.
  277'$pattr_directive'(dynamic(Spec), M) :-
  278    '$set_pattr'(Spec, M, directive, dynamic(true)).
  279'$pattr_directive'(multifile(Spec), M) :-
  280    '$set_pattr'(Spec, M, directive, multifile(true)).
  281'$pattr_directive'(module_transparent(Spec), M) :-
  282    '$set_pattr'(Spec, M, directive, transparent(true)).
  283'$pattr_directive'(discontiguous(Spec), M) :-
  284    '$set_pattr'(Spec, M, directive, discontiguous(true)).
  285'$pattr_directive'(volatile(Spec), M) :-
  286    '$set_pattr'(Spec, M, directive, volatile(true)).
  287'$pattr_directive'(thread_local(Spec), M) :-
  288    '$set_pattr'(Spec, M, directive, thread_local(true)).
  289'$pattr_directive'(noprofile(Spec), M) :-
  290    '$set_pattr'(Spec, M, directive, noprofile(true)).
  291'$pattr_directive'(public(Spec), M) :-
  292    '$set_pattr'(Spec, M, directive, public(true)).
  293'$pattr_directive'(det(Spec), M) :-
  294    '$set_pattr'(Spec, M, directive, det(true)).
 $pi_head(?PI, ?Head)
  298'$pi_head'(PI, Head) :-
  299    var(PI),
  300    var(Head),
  301    '$instantiation_error'([PI,Head]).
  302'$pi_head'(M:PI, M:Head) :-
  303    !,
  304    '$pi_head'(PI, Head).
  305'$pi_head'(Name/Arity, Head) :-
  306    !,
  307    '$head_name_arity'(Head, Name, Arity).
  308'$pi_head'(Name//DCGArity, Head) :-
  309    !,
  310    (   nonvar(DCGArity)
  311    ->  Arity is DCGArity+2,
  312	'$head_name_arity'(Head, Name, Arity)
  313    ;   '$head_name_arity'(Head, Name, Arity),
  314	DCGArity is Arity - 2
  315    ).
  316'$pi_head'(PI, _) :-
  317    '$type_error'(predicate_indicator, PI).
 $head_name_arity(+Goal, -Name, -Arity)
$head_name_arity(-Goal, +Name, +Arity)
  322'$head_name_arity'(Goal, Name, Arity) :-
  323    (   atom(Goal)
  324    ->  Name = Goal, Arity = 0
  325    ;   compound(Goal)
  326    ->  compound_name_arity(Goal, Name, Arity)
  327    ;   var(Goal)
  328    ->  (   Arity == 0
  329	->  (   atom(Name)
  330	    ->  Goal = Name
  331	    ;   Name == []
  332	    ->  Goal = Name
  333	    ;   blob(Name, closure)
  334	    ->  Goal = Name
  335	    ;   '$type_error'(atom, Name)
  336	    )
  337	;   compound_name_arity(Goal, Name, Arity)
  338	)
  339    ;   '$type_error'(callable, Goal)
  340    ).
  341
  342:- '$iso'(((dynamic)/1, (multifile)/1, (discontiguous)/1)).  343
  344
  345		/********************************
  346		*       CALLING, CONTROL        *
  347		*********************************/
  348
  349:- noprofile((call/1,
  350	      catch/3,
  351	      once/1,
  352	      ignore/1,
  353	      call_cleanup/2,
  354	      setup_call_cleanup/3,
  355	      setup_call_catcher_cleanup/4,
  356	      notrace/1)).  357
  358:- meta_predicate
  359    ';'(0,0),
  360    ','(0,0),
  361    @(0,+),
  362    call(0),
  363    call(1,?),
  364    call(2,?,?),
  365    call(3,?,?,?),
  366    call(4,?,?,?,?),
  367    call(5,?,?,?,?,?),
  368    call(6,?,?,?,?,?,?),
  369    call(7,?,?,?,?,?,?,?),
  370    not(0),
  371    \+(0),
  372    $(0),
  373    '->'(0,0),
  374    '*->'(0,0),
  375    once(0),
  376    ignore(0),
  377    catch(0,?,0),
  378    reset(0,?,-),
  379    setup_call_cleanup(0,0,0),
  380    setup_call_catcher_cleanup(0,0,?,0),
  381    call_cleanup(0,0),
  382    catch_with_backtrace(0,?,0),
  383    notrace(0),
  384    '$meta_call'(0).  385
  386:- '$iso'((call/1, (\+)/1, once/1, (;)/2, (',')/2, (->)/2, catch/3)).  387
  388% The control structures are always compiled, both   if they appear in a
  389% clause body and if they are handed  to   call/1.  The only way to call
  390% these predicates is by means of  call/2..   In  that case, we call the
  391% hole control structure again to get it compiled by call/1 and properly
  392% deal  with  !,  etc.  Another  reason  for  having  these  things   as
  393% predicates is to be able to define   properties for them, helping code
  394% analyzers.
  395
  396(M0:If ; M0:Then) :- !, call(M0:(If ; Then)).
  397(M1:If ; M2:Then) :-    call(M1:(If ; M2:Then)).
  398(G1   , G2)       :-    call((G1   , G2)).
  399(If  -> Then)     :-    call((If  -> Then)).
  400(If *-> Then)     :-    call((If *-> Then)).
  401@(Goal,Module)    :-    @(Goal,Module).
 $meta_call(:Goal)
Interpreted meta-call implementation. By default, call/1 compiles its argument into a temporary clause. This realises better performance if the (complex) goal does a lot of backtracking because this interpreted version needs to re-interpret the remainder of the goal after backtracking.

This implementation is used by reset/3 because the continuation cannot be captured if it contains a such a compiled temporary clause.

  415'$meta_call'(M:G) :-
  416    prolog_current_choice(Ch),
  417    '$meta_call'(G, M, Ch).
  418
  419'$meta_call'(Var, _, _) :-
  420    var(Var),
  421    !,
  422    '$instantiation_error'(Var).
  423'$meta_call'((A,B), M, Ch) :-
  424    !,
  425    '$meta_call'(A, M, Ch),
  426    '$meta_call'(B, M, Ch).
  427'$meta_call'((I->T;E), M, Ch) :-
  428    !,
  429    (   prolog_current_choice(Ch2),
  430	'$meta_call'(I, M, Ch2)
  431    ->  '$meta_call'(T, M, Ch)
  432    ;   '$meta_call'(E, M, Ch)
  433    ).
  434'$meta_call'((I*->T;E), M, Ch) :-
  435    !,
  436    (   prolog_current_choice(Ch2),
  437	'$meta_call'(I, M, Ch2)
  438    *-> '$meta_call'(T, M, Ch)
  439    ;   '$meta_call'(E, M, Ch)
  440    ).
  441'$meta_call'((I->T), M, Ch) :-
  442    !,
  443    (   prolog_current_choice(Ch2),
  444	'$meta_call'(I, M, Ch2)
  445    ->  '$meta_call'(T, M, Ch)
  446    ).
  447'$meta_call'((I*->T), M, Ch) :-
  448    !,
  449    prolog_current_choice(Ch2),
  450    '$meta_call'(I, M, Ch2),
  451    '$meta_call'(T, M, Ch).
  452'$meta_call'((A;B), M, Ch) :-
  453    !,
  454    (   '$meta_call'(A, M, Ch)
  455    ;   '$meta_call'(B, M, Ch)
  456    ).
  457'$meta_call'(\+(G), M, _) :-
  458    !,
  459    prolog_current_choice(Ch),
  460    \+ '$meta_call'(G, M, Ch).
  461'$meta_call'($(G), M, _) :-
  462    !,
  463    prolog_current_choice(Ch),
  464    $('$meta_call'(G, M, Ch)).
  465'$meta_call'(call(G), M, _) :-
  466    !,
  467    prolog_current_choice(Ch),
  468    '$meta_call'(G, M, Ch).
  469'$meta_call'(M:G, _, Ch) :-
  470    !,
  471    '$meta_call'(G, M, Ch).
  472'$meta_call'(!, _, Ch) :-
  473    prolog_cut_to(Ch).
  474'$meta_call'(G, M, _Ch) :-
  475    call(M:G).
 call(:Closure, ?A)
 call(:Closure, ?A1, ?A2)
 call(:Closure, ?A1, ?A2, ?A3)
 call(:Closure, ?A1, ?A2, ?A3, ?A4)
 call(:Closure, ?A1, ?A2, ?A3, ?A4, ?A5)
 call(:Closure, ?A1, ?A2, ?A3, ?A4, ?A5, ?A6)
 call(:Closure, ?A1, ?A2, ?A3, ?A4, ?A5, ?A6, ?A7)
Arity 2..8 is demanded by the ISO standard. Higher arities are supported, but handled by the compiler. This implies they are not backed up by predicates and analyzers thus cannot ask for their properties. Analyzers should hard-code handling of call/2..
  491:- '$iso'((call/2,
  492	   call/3,
  493	   call/4,
  494	   call/5,
  495	   call/6,
  496	   call/7,
  497	   call/8)).  498
  499call(Goal) :-                           % make these available as predicates
  500    Goal.
  501call(Goal, A) :-
  502    call(Goal, A).
  503call(Goal, A, B) :-
  504    call(Goal, A, B).
  505call(Goal, A, B, C) :-
  506    call(Goal, A, B, C).
  507call(Goal, A, B, C, D) :-
  508    call(Goal, A, B, C, D).
  509call(Goal, A, B, C, D, E) :-
  510    call(Goal, A, B, C, D, E).
  511call(Goal, A, B, C, D, E, F) :-
  512    call(Goal, A, B, C, D, E, F).
  513call(Goal, A, B, C, D, E, F, G) :-
  514    call(Goal, A, B, C, D, E, F, G).
 not(:Goal) is semidet
Pre-ISO version of \+/1. Note that some systems define not/1 as a logically more sound version of \+/1.
  521not(Goal) :-
  522    \+ Goal.
 \+ :Goal is semidet
Predicate version that allows for meta-calling.
  528\+ Goal :-
  529    \+ Goal.
 once(:Goal) is semidet
ISO predicate, acting as call((Goal, !)).
  535once(Goal) :-
  536    Goal,
  537    !.
 ignore(:Goal) is det
Call Goal, cut choice-points on success and succeed on failure. intended for calling side-effects and proceed on failure.
  544ignore(Goal) :-
  545    Goal,
  546    !.
  547ignore(_Goal).
  548
  549:- '$iso'((false/0)).
 false
Synonym for fail/0, providing a declarative reading.
  555false :-
  556    fail.
 catch(:Goal, +Catcher, :Recover)
ISO compliant exception handling.
  562catch(_Goal, _Catcher, _Recover) :-
  563    '$catch'.                       % Maps to I_CATCH, I_EXITCATCH
 prolog_cut_to(+Choice)
Cut all choice points after Choice
  569prolog_cut_to(_Choice) :-
  570    '$cut'.                         % Maps to I_CUTCHP
 $ is det
Declare that from now on this predicate succeeds deterministically.
  576'$' :- '$'.
 $ :Goal is det
Declare that Goal must succeed deterministically.
  582$(Goal) :- $(Goal).
 notrace(:Goal) is semidet
Suspend the tracer while running Goal.
  588:- '$hide'(notrace/1).  589
  590notrace(Goal) :-
  591    setup_call_cleanup(
  592	'$notrace'(Flags, SkipLevel),
  593	once(Goal),
  594	'$restore_trace'(Flags, SkipLevel)).
 reset(:Goal, ?Ball, -Continue)
Delimited continuation support.
  601reset(_Goal, _Ball, _Cont) :-
  602    '$reset'.
 shift(+Ball)
 shift_for_copy(+Ball)
Shift control back to the enclosing reset/3. The second version assumes the continuation will be saved to be reused in a different context.
  611shift(Ball) :-
  612    '$shift'(Ball).
  613
  614shift_for_copy(Ball) :-
  615    '$shift_for_copy'(Ball).
 call_continuation(+Continuation:list)
Call a continuation as created by shift/1. The continuation is a list of '$cont$'(Clause, PC, EnvironmentArg, ...) structures. The predicate '$call_one_tail_body'/1 creates a frame from the continuation and calls this.

Note that we can technically also push the entire continuation onto the environment and call it. Doing it incrementally as below exploits last-call optimization and therefore possible quadratic expansion of the continuation.

  629call_continuation([]).
  630call_continuation([TB|Rest]) :-
  631    (   Rest == []
  632    ->  '$call_continuation'(TB)
  633    ;   '$call_continuation'(TB),
  634	call_continuation(Rest)
  635    ).
 catch_with_backtrace(:Goal, ?Ball, :Recover)
As catch/3, but tell library(prolog_stack) to record a backtrace in case of an exception.
  642catch_with_backtrace(Goal, Ball, Recover) :-
  643    catch(Goal, Ball, Recover),
  644    '$no_lco'.
  645
  646'$no_lco'.
 $recover_and_rethrow(:Goal, +Term)
This goal is used to wrap the catch/3 recover handler if the exception is not supposed to be `catchable'. An example of an uncachable exception is '$aborted', used by abort/0. Note that we cut to ensure that the exception is not delayed forever because the recover handler leaves a choicepoint.
  656:- public '$recover_and_rethrow'/2.  657
  658'$recover_and_rethrow'(Goal, Exception) :-
  659    call_cleanup(Goal, throw(Exception)),
  660    !.
 call_cleanup(:Goal, :Cleanup)
 setup_call_cleanup(:Setup, :Goal, :Cleanup)
 setup_call_catcher_cleanup(:Setup, :Goal, +Catcher, :Cleanup)
Call Cleanup once after Goal is finished (deterministic success, failure, exception or cut). The call to '$call_cleanup' is translated to I_CALLCLEANUP, I_EXITCLEANUP. These instructions rely on the exact stack layout left by these predicates, where the variant is determined by the arity. See also callCleanupHandler() in pl-wam.c.
  674setup_call_catcher_cleanup(Setup, _Goal, _Catcher, _Cleanup) :-
  675    sig_atomic(Setup),
  676    '$call_cleanup'.
  677
  678setup_call_cleanup(Setup, _Goal, _Cleanup) :-
  679    sig_atomic(Setup),
  680    '$call_cleanup'.
  681
  682call_cleanup(_Goal, _Cleanup) :-
  683    '$call_cleanup'.
  684
  685
  686		 /*******************************
  687		 *       INITIALIZATION         *
  688		 *******************************/
  689
  690:- meta_predicate
  691    initialization(0, +).  692
  693:- multifile '$init_goal'/3.  694:- dynamic   '$init_goal'/3.
 initialization(:Goal, +When)
Register Goal to be executed if a saved state is restored. In addition, the goal is executed depending on When:
now
Execute immediately
after_load
Execute after loading the file in which it appears. This is initialization/1.
restore_state
Do not execute immediately, but only when restoring the state. Not allowed in a sandboxed environment.
prepare_state
Called before saving a state. Can be used to clean the environment (see also volatile/1) or eagerly execute goals that are normally executed lazily.
program
Works as -g goal goals.
main
Starts the application. Only last declaration is used.

Note that all goals are executed when a program is restored.

  720initialization(Goal, When) :-
  721    '$must_be'(oneof(atom, initialization_type,
  722		     [ now,
  723		       after_load,
  724		       restore,
  725		       restore_state,
  726		       prepare_state,
  727		       program,
  728		       main
  729		     ]), When),
  730    '$initialization_context'(Source, Ctx),
  731    '$initialization'(When, Goal, Source, Ctx).
  732
  733'$initialization'(now, Goal, _Source, Ctx) :-
  734    '$run_init_goal'(Goal, Ctx),
  735    '$compile_init_goal'(-, Goal, Ctx).
  736'$initialization'(after_load, Goal, Source, Ctx) :-
  737    (   Source \== (-)
  738    ->  '$compile_init_goal'(Source, Goal, Ctx)
  739    ;   throw(error(context_error(nodirective,
  740				  initialization(Goal, after_load)),
  741		    _))
  742    ).
  743'$initialization'(restore, Goal, Source, Ctx) :- % deprecated
  744    '$initialization'(restore_state, Goal, Source, Ctx).
  745'$initialization'(restore_state, Goal, _Source, Ctx) :-
  746    (   \+ current_prolog_flag(sandboxed_load, true)
  747    ->  '$compile_init_goal'(-, Goal, Ctx)
  748    ;   '$permission_error'(register, initialization(restore), Goal)
  749    ).
  750'$initialization'(prepare_state, Goal, _Source, Ctx) :-
  751    (   \+ current_prolog_flag(sandboxed_load, true)
  752    ->  '$compile_init_goal'(when(prepare_state), Goal, Ctx)
  753    ;   '$permission_error'(register, initialization(restore), Goal)
  754    ).
  755'$initialization'(program, Goal, _Source, Ctx) :-
  756    (   \+ current_prolog_flag(sandboxed_load, true)
  757    ->  '$compile_init_goal'(when(program), Goal, Ctx)
  758    ;   '$permission_error'(register, initialization(restore), Goal)
  759    ).
  760'$initialization'(main, Goal, _Source, Ctx) :-
  761    (   \+ current_prolog_flag(sandboxed_load, true)
  762    ->  '$compile_init_goal'(when(main), Goal, Ctx)
  763    ;   '$permission_error'(register, initialization(restore), Goal)
  764    ).
  765
  766
  767'$compile_init_goal'(Source, Goal, Ctx) :-
  768    atom(Source),
  769    Source \== (-),
  770    !,
  771    '$store_admin_clause'(system:'$init_goal'(Source, Goal, Ctx),
  772			  _Layout, Source, Ctx).
  773'$compile_init_goal'(Source, Goal, Ctx) :-
  774    assertz('$init_goal'(Source, Goal, Ctx)).
 $run_initialization(?File, +Options) is det
 $run_initialization(?File, +Action, +Options) is det
Run initialization directives for all files if File is unbound, or for a specified file. Note that '$run_initialization'/2 is called from runInitialization() in pl-wic.c for .qlf files. The '$run_initialization'/3 is called with Action set to loaded when called for a QLF file.
  786'$run_initialization'(_, loaded, _) :- !.
  787'$run_initialization'(File, _Action, Options) :-
  788    '$run_initialization'(File, Options).
  789
  790'$run_initialization'(File, Options) :-
  791    setup_call_cleanup(
  792	'$start_run_initialization'(Options, Restore),
  793	'$run_initialization_2'(File),
  794	'$end_run_initialization'(Restore)).
  795
  796'$start_run_initialization'(Options, OldSandBoxed) :-
  797    '$push_input_context'(initialization),
  798    '$set_sandboxed_load'(Options, OldSandBoxed).
  799'$end_run_initialization'(OldSandBoxed) :-
  800    set_prolog_flag(sandboxed_load, OldSandBoxed),
  801    '$pop_input_context'.
  802
  803'$run_initialization_2'(File) :-
  804    (   '$init_goal'(File, Goal, Ctx),
  805	File \= when(_),
  806	'$run_init_goal'(Goal, Ctx),
  807	fail
  808    ;   true
  809    ).
  810
  811'$run_init_goal'(Goal, Ctx) :-
  812    (   catch_with_backtrace('$run_init_goal'(Goal), E,
  813			     '$initialization_error'(E, Goal, Ctx))
  814    ->  true
  815    ;   '$initialization_failure'(Goal, Ctx)
  816    ).
  817
  818:- multifile prolog:sandbox_allowed_goal/1.  819
  820'$run_init_goal'(Goal) :-
  821    current_prolog_flag(sandboxed_load, false),
  822    !,
  823    call(Goal).
  824'$run_init_goal'(Goal) :-
  825    prolog:sandbox_allowed_goal(Goal),
  826    call(Goal).
  827
  828'$initialization_context'(Source, Ctx) :-
  829    (   source_location(File, Line)
  830    ->  Ctx = File:Line,
  831	'$input_context'(Context),
  832	'$top_file'(Context, File, Source)
  833    ;   Ctx = (-),
  834	File = (-)
  835    ).
  836
  837'$top_file'([input(include, F1, _, _)|T], _, F) :-
  838    !,
  839    '$top_file'(T, F1, F).
  840'$top_file'(_, F, F).
  841
  842
  843'$initialization_error'(E, Goal, Ctx) :-
  844    print_message(error, initialization_error(Goal, E, Ctx)).
  845
  846'$initialization_failure'(Goal, Ctx) :-
  847    print_message(warning, initialization_failure(Goal, Ctx)).
 $clear_source_admin(+File) is det
Removes source adminstration related to File
See also
- Called from destroySourceFile() in pl-proc.c
  855:- public '$clear_source_admin'/1.  856
  857'$clear_source_admin'(File) :-
  858    retractall('$init_goal'(_, _, File:_)),
  859    retractall('$load_context_module'(File, _, _)),
  860    retractall('$resolved_source_path_db'(_, _, File)).
  861
  862
  863		 /*******************************
  864		 *            STREAM            *
  865		 *******************************/
  866
  867:- '$iso'(stream_property/2).  868stream_property(Stream, Property) :-
  869    nonvar(Stream),
  870    nonvar(Property),
  871    !,
  872    '$stream_property'(Stream, Property).
  873stream_property(Stream, Property) :-
  874    nonvar(Stream),
  875    !,
  876    '$stream_properties'(Stream, Properties),
  877    '$member'(Property, Properties).
  878stream_property(Stream, Property) :-
  879    nonvar(Property),
  880    !,
  881    (   Property = alias(Alias),
  882	atom(Alias)
  883    ->  '$alias_stream'(Alias, Stream)
  884    ;   '$streams_properties'(Property, Pairs),
  885	'$member'(Stream-Property, Pairs)
  886    ).
  887stream_property(Stream, Property) :-
  888    '$streams_properties'(Property, Pairs),
  889    '$member'(Stream-Properties, Pairs),
  890    '$member'(Property, Properties).
  891
  892
  893		/********************************
  894		*            MODULES            *
  895		*********************************/
  896
  897%       '$prefix_module'(+Module, +Context, +Term, -Prefixed)
  898%       Tags `Term' with `Module:' if `Module' is not the context module.
  899
  900'$prefix_module'(Module, Module, Head, Head) :- !.
  901'$prefix_module'(Module, _, Head, Module:Head).
 default_module(+Me, -Super) is multi
Is true if `Super' is `Me' or a super (auto import) module of `Me'.
  907default_module(Me, Super) :-
  908    (   atom(Me)
  909    ->  (   var(Super)
  910	->  '$default_module'(Me, Super)
  911	;   '$default_module'(Me, Super), !
  912	)
  913    ;   '$type_error'(module, Me)
  914    ).
  915
  916'$default_module'(Me, Me).
  917'$default_module'(Me, Super) :-
  918    import_module(Me, S),
  919    '$default_module'(S, Super).
  920
  921
  922		/********************************
  923		*      TRACE AND EXCEPTIONS     *
  924		*********************************/
  925
  926:- dynamic   user:exception/3.  927:- multifile user:exception/3.  928:- '$hide'(user:exception/3).
 $undefined_procedure(+Module, +Name, +Arity, -Action) is det
This predicate is called from C on undefined predicates. First allows the user to take care of it using exception/3. Else try to give a DWIM warning. Otherwise fail. C will print an error message.
  937:- public
  938    '$undefined_procedure'/4.  939
  940'$undefined_procedure'(Module, Name, Arity, Action) :-
  941    '$prefix_module'(Module, user, Name/Arity, Pred),
  942    user:exception(undefined_predicate, Pred, Action0),
  943    !,
  944    Action = Action0.
  945'$undefined_procedure'(Module, Name, Arity, Action) :-
  946    \+ current_prolog_flag(autoload, false),
  947    '$autoload'(Module:Name/Arity),
  948    !,
  949    Action = retry.
  950'$undefined_procedure'(_, _, _, error).
 $loading(+Library)
True if the library is being loaded. Just testing that the predicate is defined is not good enough as the file may be partly loaded. Calling use_module/2 at any time has two drawbacks: it queries the filesystem, causing slowdown and it stops libraries being autoloaded from a saved state where the library is already loaded, but the source may not be accessible.
  962'$loading'(Library) :-
  963    current_prolog_flag(threads, true),
  964    (   '$loading_file'(Library, _Queue, _LoadThread)
  965    ->  true
  966    ;   '$loading_file'(FullFile, _Queue, _LoadThread),
  967	file_name_extension(Library, _, FullFile)
  968    ->  true
  969    ).
  970
  971%        handle debugger 'w', 'p' and <N> depth options.
  972
  973'$set_debugger_write_options'(write) :-
  974    !,
  975    create_prolog_flag(debugger_write_options,
  976		       [ quoted(true),
  977			 attributes(dots),
  978			 spacing(next_argument)
  979		       ], []).
  980'$set_debugger_write_options'(print) :-
  981    !,
  982    create_prolog_flag(debugger_write_options,
  983		       [ quoted(true),
  984			 portray(true),
  985			 max_depth(10),
  986			 attributes(portray),
  987			 spacing(next_argument)
  988		       ], []).
  989'$set_debugger_write_options'(Depth) :-
  990    current_prolog_flag(debugger_write_options, Options0),
  991    (   '$select'(max_depth(_), Options0, Options)
  992    ->  true
  993    ;   Options = Options0
  994    ),
  995    create_prolog_flag(debugger_write_options,
  996		       [max_depth(Depth)|Options], []).
  997
  998
  999		/********************************
 1000		*        SYSTEM MESSAGES        *
 1001		*********************************/
 $confirm(Spec) is semidet
Ask the user to confirm a question. Spec is a term as used for print_message/2. It is printed the the query channel. This predicate may be hooked using confirm/2, which must return a boolean.
 1010:- multifile
 1011    prolog:confirm/2. 1012
 1013'$confirm'(Spec) :-
 1014    prolog:confirm(Spec, Result),
 1015    !,
 1016    Result == true.
 1017'$confirm'(Spec) :-
 1018    print_message(query, Spec),
 1019    between(0, 5, _),
 1020	get_single_char(Answer),
 1021	(   '$in_reply'(Answer, 'yYjJ \n')
 1022	->  !,
 1023	    print_message(query, if_tty([yes-[]]))
 1024	;   '$in_reply'(Answer, 'nN')
 1025	->  !,
 1026	    print_message(query, if_tty([no-[]])),
 1027	    fail
 1028	;   print_message(help, query(confirm)),
 1029	    fail
 1030	).
 1031
 1032'$in_reply'(Code, Atom) :-
 1033    char_code(Char, Code),
 1034    sub_atom(Atom, _, _, _, Char),
 1035    !.
 1036
 1037:- dynamic
 1038    user:portray/1. 1039:- multifile
 1040    user:portray/1. 1041
 1042
 1043		 /*******************************
 1044		 *       FILE_SEARCH_PATH       *
 1045		 *******************************/
 1046
 1047:- dynamic
 1048    user:file_search_path/2,
 1049    user:library_directory/1. 1050:- multifile
 1051    user:file_search_path/2,
 1052    user:library_directory/1. 1053
 1054user:(file_search_path(library, Dir) :-
 1055	library_directory(Dir)).
 1056user:file_search_path(swi, Home) :-
 1057    current_prolog_flag(home, Home).
 1058user:file_search_path(swi, Home) :-
 1059    current_prolog_flag(shared_home, Home).
 1060user:file_search_path(library, app_config(lib)).
 1061user:file_search_path(library, swi(library)).
 1062user:file_search_path(library, swi(library/clp)).
 1063user:file_search_path(foreign, swi(ArchLib)) :-
 1064    current_prolog_flag(apple_universal_binary, true),
 1065    ArchLib = 'lib/fat-darwin'.
 1066user:file_search_path(foreign, swi(ArchLib)) :-
 1067    \+ current_prolog_flag(windows, true),
 1068    current_prolog_flag(arch, Arch),
 1069    atom_concat('lib/', Arch, ArchLib).
 1070user:file_search_path(foreign, swi(ArchLib)) :-
 1071    current_prolog_flag(msys2, true),
 1072    current_prolog_flag(arch, Arch),
 1073    atomic_list_concat([lib, Arch], /, ArchLib).
 1074user:file_search_path(foreign, swi(SoLib)) :-
 1075    current_prolog_flag(msys2, true),
 1076    current_prolog_flag(arch, Arch),
 1077    atomic_list_concat([bin, Arch], /, SoLib).
 1078user:file_search_path(foreign, swi(SoLib)) :-
 1079    (   current_prolog_flag(windows, true)
 1080    ->  SoLib = bin
 1081    ;   SoLib = lib
 1082    ).
 1083user:file_search_path(path, Dir) :-
 1084    getenv('PATH', Path),
 1085    (   current_prolog_flag(windows, true)
 1086    ->  atomic_list_concat(Dirs, (;), Path)
 1087    ;   atomic_list_concat(Dirs, :, Path)
 1088    ),
 1089    '$member'(Dir, Dirs).
 1090user:file_search_path(user_app_data, Dir) :-
 1091    '$xdg_prolog_directory'(data, Dir).
 1092user:file_search_path(common_app_data, Dir) :-
 1093    '$xdg_prolog_directory'(common_data, Dir).
 1094user:file_search_path(user_app_config, Dir) :-
 1095    '$xdg_prolog_directory'(config, Dir).
 1096user:file_search_path(common_app_config, Dir) :-
 1097    '$xdg_prolog_directory'(common_config, Dir).
 1098user:file_search_path(app_data, user_app_data('.')).
 1099user:file_search_path(app_data, common_app_data('.')).
 1100user:file_search_path(app_config, user_app_config('.')).
 1101user:file_search_path(app_config, common_app_config('.')).
 1102% backward compatibility
 1103user:file_search_path(app_preferences, user_app_config('.')).
 1104user:file_search_path(user_profile, app_preferences('.')).
 1105
 1106'$xdg_prolog_directory'(Which, Dir) :-
 1107    '$xdg_directory'(Which, XDGDir),
 1108    '$make_config_dir'(XDGDir),
 1109    '$ensure_slash'(XDGDir, XDGDirS),
 1110    atom_concat(XDGDirS, 'swi-prolog', Dir),
 1111    '$make_config_dir'(Dir).
 1112
 1113% config
 1114'$xdg_directory'(config, Home) :-
 1115    current_prolog_flag(windows, true),
 1116    catch(win_folder(appdata, Home), _, fail),
 1117    !.
 1118'$xdg_directory'(config, Home) :-
 1119    getenv('XDG_CONFIG_HOME', Home).
 1120'$xdg_directory'(config, Home) :-
 1121    expand_file_name('~/.config', [Home]).
 1122% data
 1123'$xdg_directory'(data, Home) :-
 1124    current_prolog_flag(windows, true),
 1125    catch(win_folder(local_appdata, Home), _, fail),
 1126    !.
 1127'$xdg_directory'(data, Home) :-
 1128    getenv('XDG_DATA_HOME', Home).
 1129'$xdg_directory'(data, Home) :-
 1130    expand_file_name('~/.local', [Local]),
 1131    '$make_config_dir'(Local),
 1132    atom_concat(Local, '/share', Home),
 1133    '$make_config_dir'(Home).
 1134% common data
 1135'$xdg_directory'(common_data, Dir) :-
 1136    current_prolog_flag(windows, true),
 1137    catch(win_folder(common_appdata, Dir), _, fail),
 1138    !.
 1139'$xdg_directory'(common_data, Dir) :-
 1140    '$existing_dir_from_env_path'('XDG_DATA_DIRS',
 1141				  [ '/usr/local/share',
 1142				    '/usr/share'
 1143				  ],
 1144				  Dir).
 1145% common config
 1146'$xdg_directory'(common_config, Dir) :-
 1147    current_prolog_flag(windows, true),
 1148    catch(win_folder(common_appdata, Dir), _, fail),
 1149    !.
 1150'$xdg_directory'(common_config, Dir) :-
 1151    '$existing_dir_from_env_path'('XDG_CONFIG_DIRS', ['/etc/xdg'], Dir).
 1152
 1153'$existing_dir_from_env_path'(Env, Defaults, Dir) :-
 1154    (   getenv(Env, Path)
 1155    ->  '$path_sep'(Sep),
 1156	atomic_list_concat(Dirs, Sep, Path)
 1157    ;   Dirs = Defaults
 1158    ),
 1159    '$member'(Dir, Dirs),
 1160    Dir \== '',
 1161    exists_directory(Dir).
 1162
 1163'$path_sep'(Char) :-
 1164    (   current_prolog_flag(windows, true)
 1165    ->  Char = ';'
 1166    ;   Char = ':'
 1167    ).
 1168
 1169'$make_config_dir'(Dir) :-
 1170    exists_directory(Dir),
 1171    !.
 1172'$make_config_dir'(Dir) :-
 1173    nb_current('$create_search_directories', true),
 1174    file_directory_name(Dir, Parent),
 1175    '$my_file'(Parent),
 1176    catch(make_directory(Dir), _, fail).
 1177
 1178'$ensure_slash'(Dir, DirS) :-
 1179    (   sub_atom(Dir, _, _, 0, /)
 1180    ->  DirS = Dir
 1181    ;   atom_concat(Dir, /, DirS)
 1182    ).
 $expand_file_search_path(+Spec, -Expanded, +Cond) is nondet
 1187'$expand_file_search_path'(Spec, Expanded, Cond) :-
 1188    '$option'(access(Access), Cond),
 1189    memberchk(Access, [write,append]),
 1190    !,
 1191    setup_call_cleanup(
 1192	nb_setval('$create_search_directories', true),
 1193	expand_file_search_path(Spec, Expanded),
 1194	nb_delete('$create_search_directories')).
 1195'$expand_file_search_path'(Spec, Expanded, _Cond) :-
 1196    expand_file_search_path(Spec, Expanded).
 expand_file_search_path(+Spec, -Expanded) is nondet
Expand a search path. The system uses depth-first search upto a specified depth. If this depth is exceeded an exception is raised. TBD: bread-first search?
 1204expand_file_search_path(Spec, Expanded) :-
 1205    catch('$expand_file_search_path'(Spec, Expanded, 0, []),
 1206	  loop(Used),
 1207	  throw(error(loop_error(Spec), file_search(Used)))).
 1208
 1209'$expand_file_search_path'(Spec, Expanded, N, Used) :-
 1210    functor(Spec, Alias, 1),
 1211    !,
 1212    user:file_search_path(Alias, Exp0),
 1213    NN is N + 1,
 1214    (   NN > 16
 1215    ->  throw(loop(Used))
 1216    ;   true
 1217    ),
 1218    '$expand_file_search_path'(Exp0, Exp1, NN, [Alias=Exp0|Used]),
 1219    arg(1, Spec, Segments),
 1220    '$segments_to_atom'(Segments, File),
 1221    '$make_path'(Exp1, File, Expanded).
 1222'$expand_file_search_path'(Spec, Path, _, _) :-
 1223    '$segments_to_atom'(Spec, Path).
 1224
 1225'$make_path'(Dir, '.', Path) :-
 1226    !,
 1227    Path = Dir.
 1228'$make_path'(Dir, File, Path) :-
 1229    sub_atom(Dir, _, _, 0, /),
 1230    !,
 1231    atom_concat(Dir, File, Path).
 1232'$make_path'(Dir, File, Path) :-
 1233    atomic_list_concat([Dir, /, File], Path).
 1234
 1235
 1236		/********************************
 1237		*         FILE CHECKING         *
 1238		*********************************/
 absolute_file_name(+Term, -AbsoluteFile, +Options) is nondet
Translate path-specifier into a full path-name. This predicate originates from Quintus was introduced in SWI-Prolog very early and has re-appeared in SICStus 3.9.0, where they changed argument order and added some options. We addopted the SICStus argument order, but still accept the original argument order for compatibility reasons.
 1249absolute_file_name(Spec, Options, Path) :-
 1250    '$is_options'(Options),
 1251    \+ '$is_options'(Path),
 1252    !,
 1253    '$absolute_file_name'(Spec, Path, Options).
 1254absolute_file_name(Spec, Path, Options) :-
 1255    '$absolute_file_name'(Spec, Path, Options).
 1256
 1257'$absolute_file_name'(Spec, Path, Options0) :-
 1258    '$options_dict'(Options0, Options),
 1259		    % get the valid extensions
 1260    (   '$select_option'(extensions(Exts), Options, Options1)
 1261    ->  '$must_be'(list, Exts)
 1262    ;   '$option'(file_type(Type), Options)
 1263    ->  '$must_be'(atom, Type),
 1264	'$file_type_extensions'(Type, Exts),
 1265	Options1 = Options
 1266    ;   Options1 = Options,
 1267	Exts = ['']
 1268    ),
 1269    '$canonicalise_extensions'(Exts, Extensions),
 1270		    % unless specified otherwise, ask regular file
 1271    (   (   nonvar(Type)
 1272	;   '$option'(access(none), Options, none)
 1273	)
 1274    ->  Options2 = Options1
 1275    ;   '$merge_options'(_{file_type:regular}, Options1, Options2)
 1276    ),
 1277		    % Det or nondet?
 1278    (   '$select_option'(solutions(Sols), Options2, Options3)
 1279    ->  '$must_be'(oneof(atom, solutions, [first,all]), Sols)
 1280    ;   Sols = first,
 1281	Options3 = Options2
 1282    ),
 1283		    % Errors or not?
 1284    (   '$select_option'(file_errors(FileErrors), Options3, Options4)
 1285    ->  '$must_be'(oneof(atom, file_errors, [error,fail]), FileErrors)
 1286    ;   FileErrors = error,
 1287	Options4 = Options3
 1288    ),
 1289		    % Expand shell patterns?
 1290    (   atomic(Spec),
 1291	'$select_option'(expand(Expand), Options4, Options5),
 1292	'$must_be'(boolean, Expand)
 1293    ->  expand_file_name(Spec, List),
 1294	'$member'(Spec1, List)
 1295    ;   Spec1 = Spec,
 1296	Options5 = Options4
 1297    ),
 1298		    % Search for files
 1299    (   Sols == first
 1300    ->  (   '$chk_file'(Spec1, Extensions, Options5, true, Path)
 1301	->  !       % also kill choice point of expand_file_name/2
 1302	;   (   FileErrors == fail
 1303	    ->  fail
 1304	    ;   '$current_module'('$bags', _File),
 1305		findall(P,
 1306			'$chk_file'(Spec1, Extensions, [access(exist)],
 1307				    false, P),
 1308			Candidates),
 1309		'$abs_file_error'(Spec, Candidates, Options5)
 1310	    )
 1311	)
 1312    ;   '$chk_file'(Spec1, Extensions, Options5, false, Path)
 1313    ).
 1314
 1315'$abs_file_error'(Spec, Candidates, Conditions) :-
 1316    '$member'(F, Candidates),
 1317    '$member'(C, Conditions),
 1318    '$file_condition'(C),
 1319    '$file_error'(C, Spec, F, E, Comment),
 1320    !,
 1321    throw(error(E, context(_, Comment))).
 1322'$abs_file_error'(Spec, _, _) :-
 1323    '$existence_error'(source_sink, Spec).
 1324
 1325'$file_error'(file_type(directory), Spec, File, Error, Comment) :-
 1326    \+ exists_directory(File),
 1327    !,
 1328    Error = existence_error(directory, Spec),
 1329    Comment = not_a_directory(File).
 1330'$file_error'(file_type(_), Spec, File, Error, Comment) :-
 1331    exists_directory(File),
 1332    !,
 1333    Error = existence_error(file, Spec),
 1334    Comment = directory(File).
 1335'$file_error'(access(OneOrList), Spec, File, Error, _) :-
 1336    '$one_or_member'(Access, OneOrList),
 1337    \+ access_file(File, Access),
 1338    Error = permission_error(Access, source_sink, Spec).
 1339
 1340'$one_or_member'(Elem, List) :-
 1341    is_list(List),
 1342    !,
 1343    '$member'(Elem, List).
 1344'$one_or_member'(Elem, Elem).
 1345
 1346
 1347'$file_type_extensions'(source, Exts) :-       % SICStus 3.9 compatibility
 1348    !,
 1349    '$file_type_extensions'(prolog, Exts).
 1350'$file_type_extensions'(Type, Exts) :-
 1351    '$current_module'('$bags', _File),
 1352    !,
 1353    findall(Ext, user:prolog_file_type(Ext, Type), Exts0),
 1354    (   Exts0 == [],
 1355	\+ '$ft_no_ext'(Type)
 1356    ->  '$domain_error'(file_type, Type)
 1357    ;   true
 1358    ),
 1359    '$append'(Exts0, [''], Exts).
 1360'$file_type_extensions'(prolog, [pl, '']). % findall is not yet defined ...
 1361
 1362'$ft_no_ext'(txt).
 1363'$ft_no_ext'(executable).
 1364'$ft_no_ext'(directory).
 1365'$ft_no_ext'(regular).
 user:prolog_file_type(?Extension, ?Type)
Define type of file based on the extension. This is used by absolute_file_name/3 and may be used to extend the list of extensions used for some type.

Note that qlf must be last when searching for Prolog files. Otherwise use_module/1 will consider the file as not-loaded because the .qlf file is not the loaded file. Must be fixed elsewhere.

 1378:- multifile(user:prolog_file_type/2). 1379:- dynamic(user:prolog_file_type/2). 1380
 1381user:prolog_file_type(pl,       prolog).
 1382user:prolog_file_type(prolog,   prolog).
 1383user:prolog_file_type(qlf,      prolog).
 1384user:prolog_file_type(qlf,      qlf).
 1385user:prolog_file_type(Ext,      executable) :-
 1386    current_prolog_flag(shared_object_extension, Ext).
 1387user:prolog_file_type(dylib,    executable) :-
 1388    current_prolog_flag(apple,  true).
 $chk_file(+Spec, +Extensions, +Cond, +UseCache, -FullName)
File is a specification of a Prolog source file. Return the full path of the file.
 1395'$chk_file'(Spec, _Extensions, _Cond, _Cache, _FullName) :-
 1396    \+ ground(Spec),
 1397    !,
 1398    '$instantiation_error'(Spec).
 1399'$chk_file'(Spec, Extensions, Cond, Cache, FullName) :-
 1400    compound(Spec),
 1401    functor(Spec, _, 1),
 1402    !,
 1403    '$relative_to'(Cond, cwd, CWD),
 1404    '$chk_alias_file'(Spec, Extensions, Cond, Cache, CWD, FullName).
 1405'$chk_file'(Segments, Ext, Cond, Cache, FullName) :-    % allow a/b/...
 1406    \+ atomic(Segments),
 1407    !,
 1408    '$segments_to_atom'(Segments, Atom),
 1409    '$chk_file'(Atom, Ext, Cond, Cache, FullName).
 1410'$chk_file'(File, Exts, Cond, _, FullName) :-
 1411    is_absolute_file_name(File),
 1412    !,
 1413    '$extend_file'(File, Exts, Extended),
 1414    '$file_conditions'(Cond, Extended),
 1415    '$absolute_file_name'(Extended, FullName).
 1416'$chk_file'(File, Exts, Cond, _, FullName) :-
 1417    '$relative_to'(Cond, source, Dir),
 1418    atomic_list_concat([Dir, /, File], AbsFile),
 1419    '$extend_file'(AbsFile, Exts, Extended),
 1420    '$file_conditions'(Cond, Extended),
 1421    !,
 1422    '$absolute_file_name'(Extended, FullName).
 1423'$chk_file'(File, Exts, Cond, _, FullName) :-
 1424    '$extend_file'(File, Exts, Extended),
 1425    '$file_conditions'(Cond, Extended),
 1426    '$absolute_file_name'(Extended, FullName).
 1427
 1428'$segments_to_atom'(Atom, Atom) :-
 1429    atomic(Atom),
 1430    !.
 1431'$segments_to_atom'(Segments, Atom) :-
 1432    '$segments_to_list'(Segments, List, []),
 1433    !,
 1434    atomic_list_concat(List, /, Atom).
 1435
 1436'$segments_to_list'(A/B, H, T) :-
 1437    '$segments_to_list'(A, H, T0),
 1438    '$segments_to_list'(B, T0, T).
 1439'$segments_to_list'(A, [A|T], T) :-
 1440    atomic(A).
 $relative_to(+Condition, +Default, -Dir)
Determine the directory to work from. This can be specified explicitely using one or more relative_to(FileOrDir) options or implicitely relative to the working directory or current source-file.
 1450'$relative_to'(Conditions, Default, Dir) :-
 1451    (   '$option'(relative_to(FileOrDir), Conditions)
 1452    *-> (   exists_directory(FileOrDir)
 1453	->  Dir = FileOrDir
 1454	;   atom_concat(Dir, /, FileOrDir)
 1455	->  true
 1456	;   file_directory_name(FileOrDir, Dir)
 1457	)
 1458    ;   Default == cwd
 1459    ->  '$cwd'(Dir)
 1460    ;   Default == source
 1461    ->  source_location(ContextFile, _Line),
 1462	file_directory_name(ContextFile, Dir)
 1463    ).
 $chk_alias_file(+Spec, +Exts, +Cond, +Cache, +CWD, -FullFile) is nondet
 1468:- dynamic
 1469    '$search_path_file_cache'/3,    % SHA1, Time, Path
 1470    '$search_path_gc_time'/1.       % Time
 1471:- volatile
 1472    '$search_path_file_cache'/3,
 1473    '$search_path_gc_time'/1. 1474
 1475:- create_prolog_flag(file_search_cache_time, 10, []). 1476
 1477'$chk_alias_file'(Spec, Exts, Cond, true, CWD, FullFile) :-
 1478    !,
 1479    findall(Exp, '$expand_file_search_path'(Spec, Exp, Cond), Expansions),
 1480    current_prolog_flag(emulated_dialect, Dialect),
 1481    Cache = cache(Exts, Cond, CWD, Expansions, Dialect),
 1482    variant_sha1(Spec+Cache, SHA1),
 1483    get_time(Now),
 1484    current_prolog_flag(file_search_cache_time, TimeOut),
 1485    (   '$search_path_file_cache'(SHA1, CachedTime, FullFile),
 1486	CachedTime > Now - TimeOut,
 1487	'$file_conditions'(Cond, FullFile)
 1488    ->  '$search_message'(file_search(cache(Spec, Cond), FullFile))
 1489    ;   '$member'(Expanded, Expansions),
 1490	'$extend_file'(Expanded, Exts, LibFile),
 1491	(   '$file_conditions'(Cond, LibFile),
 1492	    '$absolute_file_name'(LibFile, FullFile),
 1493	    '$cache_file_found'(SHA1, Now, TimeOut, FullFile)
 1494	->  '$search_message'(file_search(found(Spec, Cond), FullFile))
 1495	;   '$search_message'(file_search(tried(Spec, Cond), LibFile)),
 1496	    fail
 1497	)
 1498    ).
 1499'$chk_alias_file'(Spec, Exts, Cond, false, _CWD, FullFile) :-
 1500    '$expand_file_search_path'(Spec, Expanded, Cond),
 1501    '$extend_file'(Expanded, Exts, LibFile),
 1502    '$file_conditions'(Cond, LibFile),
 1503    '$absolute_file_name'(LibFile, FullFile).
 1504
 1505'$cache_file_found'(_, _, TimeOut, _) :-
 1506    TimeOut =:= 0,
 1507    !.
 1508'$cache_file_found'(SHA1, Now, TimeOut, FullFile) :-
 1509    '$search_path_file_cache'(SHA1, Saved, FullFile),
 1510    !,
 1511    (   Now - Saved < TimeOut/2
 1512    ->  true
 1513    ;   retractall('$search_path_file_cache'(SHA1, _, _)),
 1514	asserta('$search_path_file_cache'(SHA1, Now, FullFile))
 1515    ).
 1516'$cache_file_found'(SHA1, Now, TimeOut, FullFile) :-
 1517    'gc_file_search_cache'(TimeOut),
 1518    asserta('$search_path_file_cache'(SHA1, Now, FullFile)).
 1519
 1520'gc_file_search_cache'(TimeOut) :-
 1521    get_time(Now),
 1522    '$search_path_gc_time'(Last),
 1523    Now-Last < TimeOut/2,
 1524    !.
 1525'gc_file_search_cache'(TimeOut) :-
 1526    get_time(Now),
 1527    retractall('$search_path_gc_time'(_)),
 1528    assertz('$search_path_gc_time'(Now)),
 1529    Before is Now - TimeOut,
 1530    (   '$search_path_file_cache'(SHA1, Cached, FullFile),
 1531	Cached < Before,
 1532	retractall('$search_path_file_cache'(SHA1, Cached, FullFile)),
 1533	fail
 1534    ;   true
 1535    ).
 1536
 1537
 1538'$search_message'(Term) :-
 1539    current_prolog_flag(verbose_file_search, true),
 1540    !,
 1541    print_message(informational, Term).
 1542'$search_message'(_).
 $file_conditions(+Condition, +Path)
Verify Path satisfies Condition.
 1549'$file_conditions'(List, File) :-
 1550    is_list(List),
 1551    !,
 1552    \+ ( '$member'(C, List),
 1553	 '$file_condition'(C),
 1554	 \+ '$file_condition'(C, File)
 1555       ).
 1556'$file_conditions'(Map, File) :-
 1557    \+ (  get_dict(Key, Map, Value),
 1558	  C =.. [Key,Value],
 1559	  '$file_condition'(C),
 1560	 \+ '$file_condition'(C, File)
 1561       ).
 1562
 1563'$file_condition'(file_type(directory), File) :-
 1564    !,
 1565    exists_directory(File).
 1566'$file_condition'(file_type(_), File) :-
 1567    !,
 1568    \+ exists_directory(File).
 1569'$file_condition'(access(Accesses), File) :-
 1570    !,
 1571    \+ (  '$one_or_member'(Access, Accesses),
 1572	  \+ access_file(File, Access)
 1573       ).
 1574
 1575'$file_condition'(exists).
 1576'$file_condition'(file_type(_)).
 1577'$file_condition'(access(_)).
 1578
 1579'$extend_file'(File, Exts, FileEx) :-
 1580    '$ensure_extensions'(Exts, File, Fs),
 1581    '$list_to_set'(Fs, FsSet),
 1582    '$member'(FileEx, FsSet).
 1583
 1584'$ensure_extensions'([], _, []).
 1585'$ensure_extensions'([E|E0], F, [FE|E1]) :-
 1586    file_name_extension(F, E, FE),
 1587    '$ensure_extensions'(E0, F, E1).
 $list_to_set(+List, -Set) is det
Turn list into a set, keeping the left-most copy of duplicate elements. Copied from library(lists).
 1594'$list_to_set'(List, Set) :-
 1595    '$number_list'(List, 1, Numbered),
 1596    sort(1, @=<, Numbered, ONum),
 1597    '$remove_dup_keys'(ONum, NumSet),
 1598    sort(2, @=<, NumSet, ONumSet),
 1599    '$pairs_keys'(ONumSet, Set).
 1600
 1601'$number_list'([], _, []).
 1602'$number_list'([H|T0], N, [H-N|T]) :-
 1603    N1 is N+1,
 1604    '$number_list'(T0, N1, T).
 1605
 1606'$remove_dup_keys'([], []).
 1607'$remove_dup_keys'([H|T0], [H|T]) :-
 1608    H = V-_,
 1609    '$remove_same_key'(T0, V, T1),
 1610    '$remove_dup_keys'(T1, T).
 1611
 1612'$remove_same_key'([V1-_|T0], V, T) :-
 1613    V1 == V,
 1614    !,
 1615    '$remove_same_key'(T0, V, T).
 1616'$remove_same_key'(L, _, L).
 1617
 1618'$pairs_keys'([], []).
 1619'$pairs_keys'([K-_|T0], [K|T]) :-
 1620    '$pairs_keys'(T0, T).
 1621
 1622'$pairs_values'([], []).
 1623'$pairs_values'([_-V|T0], [V|T]) :-
 1624    '$pairs_values'(T0, T).
 1625
 1626/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 1627Canonicalise the extension list. Old SWI-Prolog   require  `.pl', etc, which
 1628the Quintus compatibility  requests  `pl'.   This  layer  canonicalises  all
 1629extensions to .ext
 1630- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 1631
 1632'$canonicalise_extensions'([], []) :- !.
 1633'$canonicalise_extensions'([H|T], [CH|CT]) :-
 1634    !,
 1635    '$must_be'(atom, H),
 1636    '$canonicalise_extension'(H, CH),
 1637    '$canonicalise_extensions'(T, CT).
 1638'$canonicalise_extensions'(E, [CE]) :-
 1639    '$canonicalise_extension'(E, CE).
 1640
 1641'$canonicalise_extension'('', '') :- !.
 1642'$canonicalise_extension'(DotAtom, DotAtom) :-
 1643    sub_atom(DotAtom, 0, _, _, '.'),
 1644    !.
 1645'$canonicalise_extension'(Atom, DotAtom) :-
 1646    atom_concat('.', Atom, DotAtom).
 1647
 1648
 1649		/********************************
 1650		*            CONSULT            *
 1651		*********************************/
 1652
 1653:- dynamic
 1654    user:library_directory/1,
 1655    user:prolog_load_file/2. 1656:- multifile
 1657    user:library_directory/1,
 1658    user:prolog_load_file/2. 1659
 1660:- prompt(_, '|: '). 1661
 1662:- thread_local
 1663    '$compilation_mode_store'/1,    % database, wic, qlf
 1664    '$directive_mode_store'/1.      % database, wic, qlf
 1665:- volatile
 1666    '$compilation_mode_store'/1,
 1667    '$directive_mode_store'/1. 1668
 1669'$compilation_mode'(Mode) :-
 1670    (   '$compilation_mode_store'(Val)
 1671    ->  Mode = Val
 1672    ;   Mode = database
 1673    ).
 1674
 1675'$set_compilation_mode'(Mode) :-
 1676    retractall('$compilation_mode_store'(_)),
 1677    assertz('$compilation_mode_store'(Mode)).
 1678
 1679'$compilation_mode'(Old, New) :-
 1680    '$compilation_mode'(Old),
 1681    (   New == Old
 1682    ->  true
 1683    ;   '$set_compilation_mode'(New)
 1684    ).
 1685
 1686'$directive_mode'(Mode) :-
 1687    (   '$directive_mode_store'(Val)
 1688    ->  Mode = Val
 1689    ;   Mode = database
 1690    ).
 1691
 1692'$directive_mode'(Old, New) :-
 1693    '$directive_mode'(Old),
 1694    (   New == Old
 1695    ->  true
 1696    ;   '$set_directive_mode'(New)
 1697    ).
 1698
 1699'$set_directive_mode'(Mode) :-
 1700    retractall('$directive_mode_store'(_)),
 1701    assertz('$directive_mode_store'(Mode)).
 $compilation_level(-Level) is det
True when Level reflects the nesting in files compiling other files. 0 if no files are being loaded.
 1709'$compilation_level'(Level) :-
 1710    '$input_context'(Stack),
 1711    '$compilation_level'(Stack, Level).
 1712
 1713'$compilation_level'([], 0).
 1714'$compilation_level'([Input|T], Level) :-
 1715    (   arg(1, Input, see)
 1716    ->  '$compilation_level'(T, Level)
 1717    ;   '$compilation_level'(T, Level0),
 1718	Level is Level0+1
 1719    ).
 compiling
Is true if SWI-Prolog is generating a state or qlf file or executes a `call' directive while doing this.
 1727compiling :-
 1728    \+ (   '$compilation_mode'(database),
 1729	   '$directive_mode'(database)
 1730       ).
 1731
 1732:- meta_predicate
 1733    '$ifcompiling'(0). 1734
 1735'$ifcompiling'(G) :-
 1736    (   '$compilation_mode'(database)
 1737    ->  true
 1738    ;   call(G)
 1739    ).
 1740
 1741		/********************************
 1742		*         READ SOURCE           *
 1743		*********************************/
 $load_msg_level(+Action, +NestingLevel, -StartVerbose, -EndVerbose)
 1747'$load_msg_level'(Action, Nesting, Start, Done) :-
 1748    '$update_autoload_level'([], 0),
 1749    !,
 1750    current_prolog_flag(verbose_load, Type0),
 1751    '$load_msg_compat'(Type0, Type),
 1752    (   '$load_msg_level'(Action, Nesting, Type, Start, Done)
 1753    ->  true
 1754    ).
 1755'$load_msg_level'(_, _, silent, silent).
 1756
 1757'$load_msg_compat'(true, normal) :- !.
 1758'$load_msg_compat'(false, silent) :- !.
 1759'$load_msg_compat'(X, X).
 1760
 1761'$load_msg_level'(load_file,    _, full,   informational, informational).
 1762'$load_msg_level'(include_file, _, full,   informational, informational).
 1763'$load_msg_level'(load_file,    _, normal, silent,        informational).
 1764'$load_msg_level'(include_file, _, normal, silent,        silent).
 1765'$load_msg_level'(load_file,    0, brief,  silent,        informational).
 1766'$load_msg_level'(load_file,    _, brief,  silent,        silent).
 1767'$load_msg_level'(include_file, _, brief,  silent,        silent).
 1768'$load_msg_level'(load_file,    _, silent, silent,        silent).
 1769'$load_msg_level'(include_file, _, silent, silent,        silent).
 $source_term(+From, -Read, -RLayout, -Term, -TLayout, -Stream, +Options) is nondet
Read Prolog terms from the input From. Terms are returned on backtracking. Associated resources (i.e., streams) are closed due to setup_call_cleanup/3.
Arguments:
From- is either a term stream(Id, Stream) or a file specification.
Read- is the raw term as read from the input.
Term- is the term after term-expansion. If a term is expanded into the empty list, this is returned too. This is required to be able to return the raw term in Read
Stream- is the stream from which Read is read
Options- provides additional options:
encoding(Enc)
Encoding used to open From
syntax_errors(+ErrorMode)
process_comments(+Boolean)
term_position(-Pos)
 1792'$source_term'(From, Read, RLayout, Term, TLayout, Stream, Options) :-
 1793    '$source_term'(From, Read, RLayout, Term, TLayout, Stream, [], Options),
 1794    (   Term == end_of_file
 1795    ->  !, fail
 1796    ;   Term \== begin_of_file
 1797    ).
 1798
 1799'$source_term'(Input, _,_,_,_,_,_,_) :-
 1800    \+ ground(Input),
 1801    !,
 1802    '$instantiation_error'(Input).
 1803'$source_term'(stream(Id, In, Opts),
 1804	       Read, RLayout, Term, TLayout, Stream, Parents, Options) :-
 1805    !,
 1806    '$record_included'(Parents, Id, Id, 0.0, Message),
 1807    setup_call_cleanup(
 1808	'$open_source'(stream(Id, In, Opts), In, State, Parents, Options),
 1809	'$term_in_file'(In, Read, RLayout, Term, TLayout, Stream,
 1810			[Id|Parents], Options),
 1811	'$close_source'(State, Message)).
 1812'$source_term'(File,
 1813	       Read, RLayout, Term, TLayout, Stream, Parents, Options) :-
 1814    absolute_file_name(File, Path,
 1815		       [ file_type(prolog),
 1816			 access(read)
 1817		       ]),
 1818    time_file(Path, Time),
 1819    '$record_included'(Parents, File, Path, Time, Message),
 1820    setup_call_cleanup(
 1821	'$open_source'(Path, In, State, Parents, Options),
 1822	'$term_in_file'(In, Read, RLayout, Term, TLayout, Stream,
 1823			[Path|Parents], Options),
 1824	'$close_source'(State, Message)).
 1825
 1826:- thread_local
 1827    '$load_input'/2. 1828:- volatile
 1829    '$load_input'/2. 1830
 1831'$open_source'(stream(Id, In, Opts), In,
 1832	       restore(In, StreamState, Id, Ref, Opts), Parents, _Options) :-
 1833    !,
 1834    '$context_type'(Parents, ContextType),
 1835    '$push_input_context'(ContextType),
 1836    '$prepare_load_stream'(In, Id, StreamState),
 1837    asserta('$load_input'(stream(Id), In), Ref).
 1838'$open_source'(Path, In, close(In, Path, Ref), Parents, Options) :-
 1839    '$context_type'(Parents, ContextType),
 1840    '$push_input_context'(ContextType),
 1841    '$open_source'(Path, In, Options),
 1842    '$set_encoding'(In, Options),
 1843    asserta('$load_input'(Path, In), Ref).
 1844
 1845'$context_type'([], load_file) :- !.
 1846'$context_type'(_, include).
 1847
 1848:- multifile prolog:open_source_hook/3. 1849
 1850'$open_source'(Path, In, Options) :-
 1851    prolog:open_source_hook(Path, In, Options),
 1852    !.
 1853'$open_source'(Path, In, _Options) :-
 1854    open(Path, read, In).
 1855
 1856'$close_source'(close(In, _Id, Ref), Message) :-
 1857    erase(Ref),
 1858    call_cleanup(
 1859	close(In),
 1860	'$pop_input_context'),
 1861    '$close_message'(Message).
 1862'$close_source'(restore(In, StreamState, _Id, Ref, Opts), Message) :-
 1863    erase(Ref),
 1864    call_cleanup(
 1865	'$restore_load_stream'(In, StreamState, Opts),
 1866	'$pop_input_context'),
 1867    '$close_message'(Message).
 1868
 1869'$close_message'(message(Level, Msg)) :-
 1870    !,
 1871    '$print_message'(Level, Msg).
 1872'$close_message'(_).
 $term_in_file(+In, -Read, -RLayout, -Term, -TLayout, -Stream, +Parents, +Options) is multi
True when Term is an expanded term from In. Read is a raw term (before term-expansion). Stream is the actual stream, which starts at In, but may change due to processing included files.
See also
- '$source_term'/8 for details.
 1884'$term_in_file'(In, Read, RLayout, Term, TLayout, Stream, Parents, Options) :-
 1885    Parents \= [_,_|_],
 1886    (   '$load_input'(_, Input)
 1887    ->  stream_property(Input, file_name(File))
 1888    ),
 1889    '$set_source_location'(File, 0),
 1890    '$expanded_term'(In,
 1891		     begin_of_file, 0-0, Read, RLayout, Term, TLayout,
 1892		     Stream, Parents, Options).
 1893'$term_in_file'(In, Read, RLayout, Term, TLayout, Stream, Parents, Options) :-
 1894    '$skip_script_line'(In, Options),
 1895    '$read_clause_options'(Options, ReadOptions),
 1896    '$repeat_and_read_error_mode'(ErrorMode),
 1897      read_clause(In, Raw,
 1898		  [ syntax_errors(ErrorMode),
 1899		    variable_names(Bindings),
 1900		    term_position(Pos),
 1901		    subterm_positions(RawLayout)
 1902		  | ReadOptions
 1903		  ]),
 1904      b_setval('$term_position', Pos),
 1905      b_setval('$variable_names', Bindings),
 1906      (   Raw == end_of_file
 1907      ->  !,
 1908	  (   Parents = [_,_|_]     % Included file
 1909	  ->  fail
 1910	  ;   '$expanded_term'(In,
 1911			       Raw, RawLayout, Read, RLayout, Term, TLayout,
 1912			       Stream, Parents, Options)
 1913	  )
 1914      ;   '$expanded_term'(In, Raw, RawLayout, Read, RLayout, Term, TLayout,
 1915			   Stream, Parents, Options)
 1916      ).
 1917
 1918'$read_clause_options'([], []).
 1919'$read_clause_options'([H|T0], List) :-
 1920    (   '$read_clause_option'(H)
 1921    ->  List = [H|T]
 1922    ;   List = T
 1923    ),
 1924    '$read_clause_options'(T0, T).
 1925
 1926'$read_clause_option'(syntax_errors(_)).
 1927'$read_clause_option'(term_position(_)).
 1928'$read_clause_option'(process_comment(_)).
 $repeat_and_read_error_mode(-Mode) is multi
Calls repeat/1 and return the error mode. The implemenation is like this because during part of the boot cycle expand.pl is not yet loaded.
 1936'$repeat_and_read_error_mode'(Mode) :-
 1937    (   current_predicate('$including'/0)
 1938    ->  repeat,
 1939	(   '$including'
 1940	->  Mode = dec10
 1941	;   Mode = quiet
 1942	)
 1943    ;   Mode = dec10,
 1944	repeat
 1945    ).
 1946
 1947
 1948'$expanded_term'(In, Raw, RawLayout, Read, RLayout, Term, TLayout,
 1949		 Stream, Parents, Options) :-
 1950    E = error(_,_),
 1951    catch('$expand_term'(Raw, RawLayout, Expanded, ExpandedLayout), E,
 1952	  '$print_message_fail'(E)),
 1953    (   Expanded \== []
 1954    ->  '$expansion_member'(Expanded, ExpandedLayout, Term1, Layout1)
 1955    ;   Term1 = Expanded,
 1956	Layout1 = ExpandedLayout
 1957    ),
 1958    (   nonvar(Term1), Term1 = (:-Directive), nonvar(Directive)
 1959    ->  (   Directive = include(File),
 1960	    '$current_source_module'(Module),
 1961	    '$valid_directive'(Module:include(File))
 1962	->  stream_property(In, encoding(Enc)),
 1963	    '$add_encoding'(Enc, Options, Options1),
 1964	    '$source_term'(File, Read, RLayout, Term, TLayout,
 1965			   Stream, Parents, Options1)
 1966	;   Directive = encoding(Enc)
 1967	->  set_stream(In, encoding(Enc)),
 1968	    fail
 1969	;   Term = Term1,
 1970	    Stream = In,
 1971	    Read = Raw
 1972	)
 1973    ;   Term = Term1,
 1974	TLayout = Layout1,
 1975	Stream = In,
 1976	Read = Raw,
 1977	RLayout = RawLayout
 1978    ).
 1979
 1980'$expansion_member'(Var, Layout, Var, Layout) :-
 1981    var(Var),
 1982    !.
 1983'$expansion_member'([], _, _, _) :- !, fail.
 1984'$expansion_member'(List, ListLayout, Term, Layout) :-
 1985    is_list(List),
 1986    !,
 1987    (   var(ListLayout)
 1988    ->  '$member'(Term, List)
 1989    ;   is_list(ListLayout)
 1990    ->  '$member_rep2'(Term, Layout, List, ListLayout)
 1991    ;   Layout = ListLayout,
 1992	'$member'(Term, List)
 1993    ).
 1994'$expansion_member'(X, Layout, X, Layout).
 1995
 1996% pairwise member, repeating last element of the second
 1997% list.
 1998
 1999'$member_rep2'(H1, H2, [H1|_], [H2|_]).
 2000'$member_rep2'(H1, H2, [_|T1], [T2]) :-
 2001    !,
 2002    '$member_rep2'(H1, H2, T1, [T2]).
 2003'$member_rep2'(H1, H2, [_|T1], [_|T2]) :-
 2004    '$member_rep2'(H1, H2, T1, T2).
 $add_encoding(+Enc, +Options0, -Options)
 2008'$add_encoding'(Enc, Options0, Options) :-
 2009    (   Options0 = [encoding(Enc)|_]
 2010    ->  Options = Options0
 2011    ;   Options = [encoding(Enc)|Options0]
 2012    ).
 2013
 2014
 2015:- multifile
 2016    '$included'/4.                  % Into, Line, File, LastModified
 2017:- dynamic
 2018    '$included'/4.
 $record_included(+Parents, +File, +Path, +Time, -Message) is det
Record that we included File into the head of Parents. This is troublesome when creating a QLF file because this may happen before we opened the QLF file (and we do not yet know how to open the file because we do not yet know whether this is a module file or not).

I think that the only sensible solution is to have a special statement for this, that may appear both inside and outside QLF `parts'.

 2032'$record_included'([Parent|Parents], File, Path, Time,
 2033		   message(DoneMsgLevel,
 2034			   include_file(done(Level, file(File, Path))))) :-
 2035    source_location(SrcFile, Line),
 2036    !,
 2037    '$compilation_level'(Level),
 2038    '$load_msg_level'(include_file, Level, StartMsgLevel, DoneMsgLevel),
 2039    '$print_message'(StartMsgLevel,
 2040		     include_file(start(Level,
 2041					file(File, Path)))),
 2042    '$last'([Parent|Parents], Owner),
 2043    (   (   '$compilation_mode'(database)
 2044	;   '$qlf_current_source'(Owner)
 2045	)
 2046    ->  '$store_admin_clause'(
 2047	    system:'$included'(Parent, Line, Path, Time),
 2048	    _, Owner, SrcFile:Line)
 2049    ;   '$qlf_include'(Owner, Parent, Line, Path, Time)
 2050    ).
 2051'$record_included'(_, _, _, _, true).
 $master_file(+File, -MasterFile)
Find the primary load file from included files.
 2057'$master_file'(File, MasterFile) :-
 2058    '$included'(MasterFile0, _Line, File, _Time),
 2059    !,
 2060    '$master_file'(MasterFile0, MasterFile).
 2061'$master_file'(File, File).
 2062
 2063
 2064'$skip_script_line'(_In, Options) :-
 2065    '$option'(check_script(false), Options),
 2066    !.
 2067'$skip_script_line'(In, _Options) :-
 2068    (   peek_char(In, #)
 2069    ->  skip(In, 10)
 2070    ;   true
 2071    ).
 2072
 2073'$set_encoding'(Stream, Options) :-
 2074    '$option'(encoding(Enc), Options),
 2075    !,
 2076    Enc \== default,
 2077    set_stream(Stream, encoding(Enc)).
 2078'$set_encoding'(_, _).
 2079
 2080
 2081'$prepare_load_stream'(In, Id, state(HasName,HasPos)) :-
 2082    (   stream_property(In, file_name(_))
 2083    ->  HasName = true,
 2084	(   stream_property(In, position(_))
 2085	->  HasPos = true
 2086	;   HasPos = false,
 2087	    set_stream(In, record_position(true))
 2088	)
 2089    ;   HasName = false,
 2090	set_stream(In, file_name(Id)),
 2091	(   stream_property(In, position(_))
 2092	->  HasPos = true
 2093	;   HasPos = false,
 2094	    set_stream(In, record_position(true))
 2095	)
 2096    ).
 2097
 2098'$restore_load_stream'(In, _State, Options) :-
 2099    memberchk(close(true), Options),
 2100    !,
 2101    close(In).
 2102'$restore_load_stream'(In, state(HasName, HasPos), _Options) :-
 2103    (   HasName == false
 2104    ->  set_stream(In, file_name(''))
 2105    ;   true
 2106    ),
 2107    (   HasPos == false
 2108    ->  set_stream(In, record_position(false))
 2109    ;   true
 2110    ).
 2111
 2112
 2113		 /*******************************
 2114		 *          DERIVED FILES       *
 2115		 *******************************/
 2116
 2117:- dynamic
 2118    '$derived_source_db'/3.         % Loaded, DerivedFrom, Time
 2119
 2120'$register_derived_source'(_, '-') :- !.
 2121'$register_derived_source'(Loaded, DerivedFrom) :-
 2122    retractall('$derived_source_db'(Loaded, _, _)),
 2123    time_file(DerivedFrom, Time),
 2124    assert('$derived_source_db'(Loaded, DerivedFrom, Time)).
 2125
 2126%       Auto-importing dynamic predicates is not very elegant and
 2127%       leads to problems with qsave_program/[1,2]
 2128
 2129'$derived_source'(Loaded, DerivedFrom, Time) :-
 2130    '$derived_source_db'(Loaded, DerivedFrom, Time).
 2131
 2132
 2133		/********************************
 2134		*       LOAD PREDICATES         *
 2135		*********************************/
 2136
 2137:- meta_predicate
 2138    ensure_loaded(:),
 2139    [:|+],
 2140    consult(:),
 2141    use_module(:),
 2142    use_module(:, +),
 2143    reexport(:),
 2144    reexport(:, +),
 2145    load_files(:),
 2146    load_files(:, +).
 ensure_loaded(+FileOrListOfFiles)
Load specified files, provided they where not loaded before. If the file is a module file import the public predicates into the context module.
 2154ensure_loaded(Files) :-
 2155    load_files(Files, [if(not_loaded)]).
 use_module(+FileOrListOfFiles)
Very similar to ensure_loaded/1, but insists on the loaded file to be a module file. If the file is already imported, but the public predicates are not yet imported into the context module, then do so.
 2164use_module(Files) :-
 2165    load_files(Files, [ if(not_loaded),
 2166			must_be_module(true)
 2167		      ]).
 use_module(+File, +ImportList)
As use_module/1, but takes only one file argument and imports only the specified predicates rather than all public predicates.
 2174use_module(File, Import) :-
 2175    load_files(File, [ if(not_loaded),
 2176		       must_be_module(true),
 2177		       imports(Import)
 2178		     ]).
 reexport(+Files)
As use_module/1, exporting all imported predicates.
 2184reexport(Files) :-
 2185    load_files(Files, [ if(not_loaded),
 2186			must_be_module(true),
 2187			reexport(true)
 2188		      ]).
 reexport(+File, +ImportList)
As use_module/1, re-exporting all imported predicates.
 2194reexport(File, Import) :-
 2195    load_files(File, [ if(not_loaded),
 2196		       must_be_module(true),
 2197		       imports(Import),
 2198		       reexport(true)
 2199		     ]).
 2200
 2201
 2202[X] :-
 2203    !,
 2204    consult(X).
 2205[M:F|R] :-
 2206    consult(M:[F|R]).
 2207
 2208consult(M:X) :-
 2209    X == user,
 2210    !,
 2211    flag('$user_consult', N, N+1),
 2212    NN is N + 1,
 2213    atom_concat('user://', NN, Id),
 2214    load_files(M:Id, [stream(user_input), check_script(false), silent(false)]).
 2215consult(List) :-
 2216    load_files(List, [expand(true)]).
 load_files(:File, +Options)
Common entry for all the consult derivates. File is the raw user specified file specification, possibly tagged with the module.
 2223load_files(Files) :-
 2224    load_files(Files, []).
 2225load_files(Module:Files, Options) :-
 2226    '$must_be'(list, Options),
 2227    '$load_files'(Files, Module, Options).
 2228
 2229'$load_files'(X, _, _) :-
 2230    var(X),
 2231    !,
 2232    '$instantiation_error'(X).
 2233'$load_files'([], _, _) :- !.
 2234'$load_files'(Id, Module, Options) :-   % load_files(foo, [stream(In)])
 2235    '$option'(stream(_), Options),
 2236    !,
 2237    (   atom(Id)
 2238    ->  '$load_file'(Id, Module, Options)
 2239    ;   throw(error(type_error(atom, Id), _))
 2240    ).
 2241'$load_files'(List, Module, Options) :-
 2242    List = [_|_],
 2243    !,
 2244    '$must_be'(list, List),
 2245    '$load_file_list'(List, Module, Options).
 2246'$load_files'(File, Module, Options) :-
 2247    '$load_one_file'(File, Module, Options).
 2248
 2249'$load_file_list'([], _, _).
 2250'$load_file_list'([File|Rest], Module, Options) :-
 2251    E = error(_,_),
 2252    catch('$load_one_file'(File, Module, Options), E,
 2253	  '$print_message'(error, E)),
 2254    '$load_file_list'(Rest, Module, Options).
 2255
 2256
 2257'$load_one_file'(Spec, Module, Options) :-
 2258    atomic(Spec),
 2259    '$option'(expand(Expand), Options, false),
 2260    Expand == true,
 2261    !,
 2262    expand_file_name(Spec, Expanded),
 2263    (   Expanded = [Load]
 2264    ->  true
 2265    ;   Load = Expanded
 2266    ),
 2267    '$load_files'(Load, Module, [expand(false)|Options]).
 2268'$load_one_file'(File, Module, Options) :-
 2269    strip_module(Module:File, Into, PlainFile),
 2270    '$load_file'(PlainFile, Into, Options).
 $noload(+Condition, +FullFile, +Options) is semidet
True of FullFile should not be loaded.
 2277'$noload'(true, _, _) :-
 2278    !,
 2279    fail.
 2280'$noload'(_, FullFile, _Options) :-
 2281    '$time_source_file'(FullFile, Time, system),
 2282    Time > 0.0,
 2283    !.
 2284'$noload'(not_loaded, FullFile, _) :-
 2285    source_file(FullFile),
 2286    !.
 2287'$noload'(changed, Derived, _) :-
 2288    '$derived_source'(_FullFile, Derived, LoadTime),
 2289    time_file(Derived, Modified),
 2290    Modified @=< LoadTime,
 2291    !.
 2292'$noload'(changed, FullFile, Options) :-
 2293    '$time_source_file'(FullFile, LoadTime, user),
 2294    '$modified_id'(FullFile, Modified, Options),
 2295    Modified @=< LoadTime,
 2296    !.
 2297'$noload'(exists, File, Options) :-
 2298    '$noload'(changed, File, Options).
 $qlf_file(+Spec, +PlFile, -LoadFile, -Mode, +Options) is det
Determine how to load the source. LoadFile is the file to be loaded, Mode is how to load it. Mode is one of
compile
Normal source compilation
qcompile
Compile from source, creating a QLF file in the process
qload
Load from QLF file.
stream
Load from a stream. Content can be a source or QLF file.
Arguments:
Spec- is the original search specification
PlFile- is the resolved absolute path to the Prolog file.
 2317'$qlf_file'(Spec, _, Spec, stream, Options) :-
 2318    '$option'(stream(_), Options),      % stream: no choice
 2319    !.
 2320'$qlf_file'(Spec, FullFile, FullFile, compile, _) :-
 2321    '$spec_extension'(Spec, Ext),       % user explicitly specified
 2322    user:prolog_file_type(Ext, prolog),
 2323    !.
 2324'$qlf_file'(Spec, FullFile, LoadFile, Mode, Options) :-
 2325    '$compilation_mode'(database),
 2326    file_name_extension(Base, PlExt, FullFile),
 2327    user:prolog_file_type(PlExt, prolog),
 2328    user:prolog_file_type(QlfExt, qlf),
 2329    file_name_extension(Base, QlfExt, QlfFile),
 2330    (   access_file(QlfFile, read),
 2331	(   '$qlf_out_of_date'(FullFile, QlfFile, Why)
 2332	->  (   access_file(QlfFile, write)
 2333	    ->  print_message(informational,
 2334			      qlf(recompile(Spec, FullFile, QlfFile, Why))),
 2335		Mode = qcompile,
 2336		LoadFile = FullFile
 2337	    ;   Why == old,
 2338		(   current_prolog_flag(home, PlHome),
 2339		    sub_atom(FullFile, 0, _, _, PlHome)
 2340		;   sub_atom(QlfFile, 0, _, _, 'res://')
 2341		)
 2342	    ->  print_message(silent,
 2343			      qlf(system_lib_out_of_date(Spec, QlfFile))),
 2344		Mode = qload,
 2345		LoadFile = QlfFile
 2346	    ;   print_message(warning,
 2347			      qlf(can_not_recompile(Spec, QlfFile, Why))),
 2348		Mode = compile,
 2349		LoadFile = FullFile
 2350	    )
 2351	;   Mode = qload,
 2352	    LoadFile = QlfFile
 2353	)
 2354    ->  !
 2355    ;   '$qlf_auto'(FullFile, QlfFile, Options)
 2356    ->  !, Mode = qcompile,
 2357	LoadFile = FullFile
 2358    ).
 2359'$qlf_file'(_, FullFile, FullFile, compile, _).
 $qlf_out_of_date(+PlFile, +QlfFile, -Why) is semidet
True if the QlfFile file is out-of-date because of Why. This predicate is the negation such that we can return the reason.
 2367'$qlf_out_of_date'(PlFile, QlfFile, Why) :-
 2368    (   access_file(PlFile, read)
 2369    ->  time_file(PlFile, PlTime),
 2370	time_file(QlfFile, QlfTime),
 2371	(   PlTime > QlfTime
 2372	->  Why = old                   % PlFile is newer
 2373	;   Error = error(Formal,_),
 2374	    catch('$qlf_info'(QlfFile, _CVer, _MLVer,
 2375			      _FVer, _CSig, _FSig),
 2376		  Error, true),
 2377	    nonvar(Formal)              % QlfFile is incompatible
 2378	->  Why = Error
 2379	;   fail                        % QlfFile is up-to-date and ok
 2380	)
 2381    ;   fail                            % can not read .pl; try .qlf
 2382    ).
 $qlf_auto(+PlFile, +QlfFile, +Options) is semidet
True if we create QlfFile using qcompile/2. This is determined by the option qcompile(QlfMode) or, if this is not present, by the prolog_flag qcompile.
 2390:- create_prolog_flag(qcompile, false, [type(atom)]). 2391
 2392'$qlf_auto'(PlFile, QlfFile, Options) :-
 2393    (   memberchk(qcompile(QlfMode), Options)
 2394    ->  true
 2395    ;   current_prolog_flag(qcompile, QlfMode),
 2396	\+ '$in_system_dir'(PlFile)
 2397    ),
 2398    (   QlfMode == auto
 2399    ->  true
 2400    ;   QlfMode == large,
 2401	size_file(PlFile, Size),
 2402	Size > 100000
 2403    ),
 2404    access_file(QlfFile, write).
 2405
 2406'$in_system_dir'(PlFile) :-
 2407    current_prolog_flag(home, Home),
 2408    sub_atom(PlFile, 0, _, _, Home).
 2409
 2410'$spec_extension'(File, Ext) :-
 2411    atom(File),
 2412    file_name_extension(_, Ext, File).
 2413'$spec_extension'(Spec, Ext) :-
 2414    compound(Spec),
 2415    arg(1, Spec, Arg),
 2416    '$spec_extension'(Arg, Ext).
 $load_file(+Spec, +ContextModule, +Options) is det
Load the file Spec into ContextModule controlled by Options. This wrapper deals with two cases before proceeding to the real loader:
 2428:- dynamic
 2429    '$resolved_source_path_db'/3.                % ?Spec, ?Dialect, ?Path
 2430
 2431'$load_file'(File, Module, Options) :-
 2432    '$error_count'(E0, W0),
 2433    '$load_file_e'(File, Module, Options),
 2434    '$error_count'(E1, W1),
 2435    Errors is E1-E0,
 2436    Warnings is W1-W0,
 2437    (   Errors+Warnings =:= 0
 2438    ->  true
 2439    ;   '$print_message'(silent, load_file_errors(File, Errors, Warnings))
 2440    ).
 2441
 2442:- if(current_prolog_flag(threads, true)). 2443'$error_count'(Errors, Warnings) :-
 2444    current_prolog_flag(threads, true),
 2445    !,
 2446    thread_self(Me),
 2447    thread_statistics(Me, errors, Errors),
 2448    thread_statistics(Me, warnings, Warnings).
 2449:- endif. 2450'$error_count'(Errors, Warnings) :-
 2451    statistics(errors, Errors),
 2452    statistics(warnings, Warnings).
 2453
 2454'$load_file_e'(File, Module, Options) :-
 2455    \+ memberchk(stream(_), Options),
 2456    user:prolog_load_file(Module:File, Options),
 2457    !.
 2458'$load_file_e'(File, Module, Options) :-
 2459    memberchk(stream(_), Options),
 2460    !,
 2461    '$assert_load_context_module'(File, Module, Options),
 2462    '$qdo_load_file'(File, File, Module, Options).
 2463'$load_file_e'(File, Module, Options) :-
 2464    (   '$resolved_source_path'(File, FullFile, Options)
 2465    ->  true
 2466    ;   '$resolve_source_path'(File, FullFile, Options)
 2467    ),
 2468    !,
 2469    '$mt_load_file'(File, FullFile, Module, Options).
 2470'$load_file_e'(_, _, _).
 $resolved_source_path(+File, -FullFile, +Options) is semidet
True when File has already been resolved to an absolute path.
 2476'$resolved_source_path'(File, FullFile, Options) :-
 2477    current_prolog_flag(emulated_dialect, Dialect),
 2478    '$resolved_source_path_db'(File, Dialect, FullFile),
 2479    (   '$source_file_property'(FullFile, from_state, true)
 2480    ;   '$source_file_property'(FullFile, resource, true)
 2481    ;   '$option'(if(If), Options, true),
 2482	'$noload'(If, FullFile, Options)
 2483    ),
 2484    !.
 $resolve_source_path(+File, -FullFile, +Options) is semidet
Resolve a source file specification to an absolute path. May throw existence and other errors.
 2491'$resolve_source_path'(File, FullFile, Options) :-
 2492    (   '$option'(if(If), Options),
 2493	If == exists
 2494    ->  Extra = [file_errors(fail)]
 2495    ;   Extra = []
 2496    ),
 2497    absolute_file_name(File, FullFile,
 2498		       [ file_type(prolog),
 2499			 access(read)
 2500		       | Extra
 2501		       ]),
 2502    '$register_resolved_source_path'(File, FullFile).
 2503
 2504'$register_resolved_source_path'(File, FullFile) :-
 2505    (   compound(File)
 2506    ->  current_prolog_flag(emulated_dialect, Dialect),
 2507	(   '$resolved_source_path_db'(File, Dialect, FullFile)
 2508	->  true
 2509	;   asserta('$resolved_source_path_db'(File, Dialect, FullFile))
 2510	)
 2511    ;   true
 2512    ).
 $translated_source(+Old, +New) is det
Called from loading a QLF state when source files are being renamed.
 2518:- public '$translated_source'/2. 2519'$translated_source'(Old, New) :-
 2520    forall(retract('$resolved_source_path_db'(File, Dialect, Old)),
 2521	   assertz('$resolved_source_path_db'(File, Dialect, New))).
 $register_resource_file(+FullFile) is det
If we load a file from a resource we lock it, so we never have to check the modification again.
 2528'$register_resource_file'(FullFile) :-
 2529    (   sub_atom(FullFile, 0, _, _, 'res://'),
 2530	\+ file_name_extension(_, qlf, FullFile)
 2531    ->  '$set_source_file'(FullFile, resource, true)
 2532    ;   true
 2533    ).
 $already_loaded(+File, +FullFile, +Module, +Options) is det
Called if File is already loaded. If this is a module-file, the module must be imported into the context Module. If it is not a module file, it must be reloaded.
bug
- A file may be associated with multiple modules. How do we find the `main export module'? Currently there is no good way to find out which module is associated to the file as a result of the first :- module/2 term.
 2546'$already_loaded'(_File, FullFile, Module, Options) :-
 2547    '$assert_load_context_module'(FullFile, Module, Options),
 2548    '$current_module'(LoadModules, FullFile),
 2549    !,
 2550    (   atom(LoadModules)
 2551    ->  LoadModule = LoadModules
 2552    ;   LoadModules = [LoadModule|_]
 2553    ),
 2554    '$import_from_loaded_module'(LoadModule, Module, Options).
 2555'$already_loaded'(_, _, user, _) :- !.
 2556'$already_loaded'(File, FullFile, Module, Options) :-
 2557    (   '$load_context_module'(FullFile, Module, CtxOptions),
 2558	'$load_ctx_options'(Options, CtxOptions)
 2559    ->  true
 2560    ;   '$load_file'(File, Module, [if(true)|Options])
 2561    ).
 $mt_load_file(+File, +FullFile, +Module, +Options) is det
Deal with multi-threaded loading of files. The thread that wishes to load the thread first will do so, while other threads will wait until the leader finished and than act as if the file is already loaded.

Synchronisation is handled using a message queue that exists while the file is being loaded. This synchronisation relies on the fact that thread_get_message/1 throws an existence_error if the message queue is destroyed. This is hacky. Events or condition variables would have made a cleaner design.

 2576:- dynamic
 2577    '$loading_file'/3.              % File, Queue, Thread
 2578:- volatile
 2579    '$loading_file'/3. 2580
 2581:- if(current_prolog_flag(threads, true)). 2582'$mt_load_file'(File, FullFile, Module, Options) :-
 2583    current_prolog_flag(threads, true),
 2584    !,
 2585    sig_atomic(setup_call_cleanup(
 2586		   with_mutex('$load_file',
 2587			      '$mt_start_load'(FullFile, Loading, Options)),
 2588		   '$mt_do_load'(Loading, File, FullFile, Module, Options),
 2589		   '$mt_end_load'(Loading))).
 2590:- endif. 2591'$mt_load_file'(File, FullFile, Module, Options) :-
 2592    '$option'(if(If), Options, true),
 2593    '$noload'(If, FullFile, Options),
 2594    !,
 2595    '$already_loaded'(File, FullFile, Module, Options).
 2596:- if(current_prolog_flag(threads, true)). 2597'$mt_load_file'(File, FullFile, Module, Options) :-
 2598    sig_atomic('$qdo_load_file'(File, FullFile, Module, Options)).
 2599:- else. 2600'$mt_load_file'(File, FullFile, Module, Options) :-
 2601    '$qdo_load_file'(File, FullFile, Module, Options).
 2602:- endif. 2603
 2604:- if(current_prolog_flag(threads, true)). 2605'$mt_start_load'(FullFile, queue(Queue), _) :-
 2606    '$loading_file'(FullFile, Queue, LoadThread),
 2607    \+ thread_self(LoadThread),
 2608    !.
 2609'$mt_start_load'(FullFile, already_loaded, Options) :-
 2610    '$option'(if(If), Options, true),
 2611    '$noload'(If, FullFile, Options),
 2612    !.
 2613'$mt_start_load'(FullFile, Ref, _) :-
 2614    thread_self(Me),
 2615    message_queue_create(Queue),
 2616    assertz('$loading_file'(FullFile, Queue, Me), Ref).
 2617
 2618'$mt_do_load'(queue(Queue), File, FullFile, Module, Options) :-
 2619    !,
 2620    catch(thread_get_message(Queue, _), error(_,_), true),
 2621    '$already_loaded'(File, FullFile, Module, Options).
 2622'$mt_do_load'(already_loaded, File, FullFile, Module, Options) :-
 2623    !,
 2624    '$already_loaded'(File, FullFile, Module, Options).
 2625'$mt_do_load'(_Ref, File, FullFile, Module, Options) :-
 2626    '$assert_load_context_module'(FullFile, Module, Options),
 2627    '$qdo_load_file'(File, FullFile, Module, Options).
 2628
 2629'$mt_end_load'(queue(_)) :- !.
 2630'$mt_end_load'(already_loaded) :- !.
 2631'$mt_end_load'(Ref) :-
 2632    clause('$loading_file'(_, Queue, _), _, Ref),
 2633    erase(Ref),
 2634    thread_send_message(Queue, done),
 2635    message_queue_destroy(Queue).
 2636:- endif.
 $qdo_load_file(+Spec, +FullFile, +ContextModule, +Options) is det
Switch to qcompile mode if requested by the option '$qlf'(+Out)
 2642'$qdo_load_file'(File, FullFile, Module, Options) :-
 2643    '$qdo_load_file2'(File, FullFile, Module, Action, Options),
 2644    '$register_resource_file'(FullFile),
 2645    '$run_initialization'(FullFile, Action, Options).
 2646
 2647'$qdo_load_file2'(File, FullFile, Module, Action, Options) :-
 2648    memberchk('$qlf'(QlfOut), Options),
 2649    '$stage_file'(QlfOut, StageQlf),
 2650    !,
 2651    setup_call_catcher_cleanup(
 2652	'$qstart'(StageQlf, Module, State),
 2653	'$do_load_file'(File, FullFile, Module, Action, Options),
 2654	Catcher,
 2655	'$qend'(State, Catcher, StageQlf, QlfOut)).
 2656'$qdo_load_file2'(File, FullFile, Module, Action, Options) :-
 2657    '$do_load_file'(File, FullFile, Module, Action, Options).
 2658
 2659'$qstart'(Qlf, Module, state(OldMode, OldModule)) :-
 2660    '$qlf_open'(Qlf),
 2661    '$compilation_mode'(OldMode, qlf),
 2662    '$set_source_module'(OldModule, Module).
 2663
 2664'$qend'(state(OldMode, OldModule), Catcher, StageQlf, QlfOut) :-
 2665    '$set_source_module'(_, OldModule),
 2666    '$set_compilation_mode'(OldMode),
 2667    '$qlf_close',
 2668    '$install_staged_file'(Catcher, StageQlf, QlfOut, warn).
 2669
 2670'$set_source_module'(OldModule, Module) :-
 2671    '$current_source_module'(OldModule),
 2672    '$set_source_module'(Module).
 $do_load_file(+Spec, +FullFile, +ContextModule, -Action, +Options) is det
Perform the actual loading.
 2679'$do_load_file'(File, FullFile, Module, Action, Options) :-
 2680    '$option'(derived_from(DerivedFrom), Options, -),
 2681    '$register_derived_source'(FullFile, DerivedFrom),
 2682    '$qlf_file'(File, FullFile, Absolute, Mode, Options),
 2683    (   Mode == qcompile
 2684    ->  qcompile(Module:File, Options)
 2685    ;   '$do_load_file_2'(File, Absolute, Module, Action, Options)
 2686    ).
 2687
 2688'$do_load_file_2'(File, Absolute, Module, Action, Options) :-
 2689    '$source_file_property'(Absolute, number_of_clauses, OldClauses),
 2690    statistics(cputime, OldTime),
 2691
 2692    '$setup_load'(ScopedFlags, OldSandBoxed, OldVerbose, OldAutoLevel, OldXRef,
 2693		  Options),
 2694
 2695    '$compilation_level'(Level),
 2696    '$load_msg_level'(load_file, Level, StartMsgLevel, DoneMsgLevel),
 2697    '$print_message'(StartMsgLevel,
 2698		     load_file(start(Level,
 2699				     file(File, Absolute)))),
 2700
 2701    (   memberchk(stream(FromStream), Options)
 2702    ->  Input = stream
 2703    ;   Input = source
 2704    ),
 2705
 2706    (   Input == stream,
 2707	(   '$option'(format(qlf), Options, source)
 2708	->  set_stream(FromStream, file_name(Absolute)),
 2709	    '$qload_stream'(FromStream, Module, Action, LM, Options)
 2710	;   '$consult_file'(stream(Absolute, FromStream, []),
 2711			    Module, Action, LM, Options)
 2712	)
 2713    ->  true
 2714    ;   Input == source,
 2715	file_name_extension(_, Ext, Absolute),
 2716	(   user:prolog_file_type(Ext, qlf),
 2717	    E = error(_,_),
 2718	    catch('$qload_file'(Absolute, Module, Action, LM, Options),
 2719		  E,
 2720		  print_message(warning, E))
 2721	->  true
 2722	;   '$consult_file'(Absolute, Module, Action, LM, Options)
 2723	)
 2724    ->  true
 2725    ;   '$print_message'(error, load_file(failed(File))),
 2726	fail
 2727    ),
 2728
 2729    '$import_from_loaded_module'(LM, Module, Options),
 2730
 2731    '$source_file_property'(Absolute, number_of_clauses, NewClauses),
 2732    statistics(cputime, Time),
 2733    ClausesCreated is NewClauses - OldClauses,
 2734    TimeUsed is Time - OldTime,
 2735
 2736    '$print_message'(DoneMsgLevel,
 2737		     load_file(done(Level,
 2738				    file(File, Absolute),
 2739				    Action,
 2740				    LM,
 2741				    TimeUsed,
 2742				    ClausesCreated))),
 2743
 2744    '$restore_load'(ScopedFlags, OldSandBoxed, OldVerbose, OldAutoLevel, OldXRef).
 2745
 2746'$setup_load'(ScopedFlags, OldSandBoxed, OldVerbose, OldAutoLevel, OldXRef,
 2747	      Options) :-
 2748    '$save_file_scoped_flags'(ScopedFlags),
 2749    '$set_sandboxed_load'(Options, OldSandBoxed),
 2750    '$set_verbose_load'(Options, OldVerbose),
 2751    '$set_optimise_load'(Options),
 2752    '$update_autoload_level'(Options, OldAutoLevel),
 2753    '$set_no_xref'(OldXRef).
 2754
 2755'$restore_load'(ScopedFlags, OldSandBoxed, OldVerbose, OldAutoLevel, OldXRef) :-
 2756    '$set_autoload_level'(OldAutoLevel),
 2757    set_prolog_flag(xref, OldXRef),
 2758    set_prolog_flag(verbose_load, OldVerbose),
 2759    set_prolog_flag(sandboxed_load, OldSandBoxed),
 2760    '$restore_file_scoped_flags'(ScopedFlags).
 $save_file_scoped_flags(-State) is det
 $restore_file_scoped_flags(-State) is det
Save/restore flags that are scoped to a compilation unit.
 2768'$save_file_scoped_flags'(State) :-
 2769    current_predicate(findall/3),          % Not when doing boot compile
 2770    !,
 2771    findall(SavedFlag, '$save_file_scoped_flag'(SavedFlag), State).
 2772'$save_file_scoped_flags'([]).
 2773
 2774'$save_file_scoped_flag'(Flag-Value) :-
 2775    '$file_scoped_flag'(Flag, Default),
 2776    (   current_prolog_flag(Flag, Value)
 2777    ->  true
 2778    ;   Value = Default
 2779    ).
 2780
 2781'$file_scoped_flag'(generate_debug_info, true).
 2782'$file_scoped_flag'(optimise,            false).
 2783'$file_scoped_flag'(xref,                false).
 2784
 2785'$restore_file_scoped_flags'([]).
 2786'$restore_file_scoped_flags'([Flag-Value|T]) :-
 2787    set_prolog_flag(Flag, Value),
 2788    '$restore_file_scoped_flags'(T).
 $import_from_loaded_module(+LoadedModule, +Module, +Options) is det
Import public predicates from LoadedModule into Module
 2795'$import_from_loaded_module'(LoadedModule, Module, Options) :-
 2796    LoadedModule \== Module,
 2797    atom(LoadedModule),
 2798    !,
 2799    '$option'(imports(Import), Options, all),
 2800    '$option'(reexport(Reexport), Options, false),
 2801    '$import_list'(Module, LoadedModule, Import, Reexport).
 2802'$import_from_loaded_module'(_, _, _).
 $set_verbose_load(+Options, -Old) is det
Set the verbose_load flag according to Options and unify Old with the old value.
 2810'$set_verbose_load'(Options, Old) :-
 2811    current_prolog_flag(verbose_load, Old),
 2812    (   memberchk(silent(Silent), Options)
 2813    ->  (   '$negate'(Silent, Level0)
 2814	->  '$load_msg_compat'(Level0, Level)
 2815	;   Level = Silent
 2816	),
 2817	set_prolog_flag(verbose_load, Level)
 2818    ;   true
 2819    ).
 2820
 2821'$negate'(true, false).
 2822'$negate'(false, true).
 $set_sandboxed_load(+Options, -Old) is det
Update the Prolog flag sandboxed_load from Options. Old is unified with the old flag.
Errors
- permission_error(leave, sandbox, -)
 2831'$set_sandboxed_load'(Options, Old) :-
 2832    current_prolog_flag(sandboxed_load, Old),
 2833    (   memberchk(sandboxed(SandBoxed), Options),
 2834	'$enter_sandboxed'(Old, SandBoxed, New),
 2835	New \== Old
 2836    ->  set_prolog_flag(sandboxed_load, New)
 2837    ;   true
 2838    ).
 2839
 2840'$enter_sandboxed'(Old, New, SandBoxed) :-
 2841    (   Old == false, New == true
 2842    ->  SandBoxed = true,
 2843	'$ensure_loaded_library_sandbox'
 2844    ;   Old == true, New == false
 2845    ->  throw(error(permission_error(leave, sandbox, -), _))
 2846    ;   SandBoxed = Old
 2847    ).
 2848'$enter_sandboxed'(false, true, true).
 2849
 2850'$ensure_loaded_library_sandbox' :-
 2851    source_file_property(library(sandbox), module(sandbox)),
 2852    !.
 2853'$ensure_loaded_library_sandbox' :-
 2854    load_files(library(sandbox), [if(not_loaded), silent(true)]).
 2855
 2856'$set_optimise_load'(Options) :-
 2857    (   '$option'(optimise(Optimise), Options)
 2858    ->  set_prolog_flag(optimise, Optimise)
 2859    ;   true
 2860    ).
 2861
 2862'$set_no_xref'(OldXRef) :-
 2863    (   current_prolog_flag(xref, OldXRef)
 2864    ->  true
 2865    ;   OldXRef = false
 2866    ),
 2867    set_prolog_flag(xref, false).
 $update_autoload_level(+Options, -OldLevel)
Update the '$autoload_nesting' and return the old value.
 2874:- thread_local
 2875    '$autoload_nesting'/1. 2876
 2877'$update_autoload_level'(Options, AutoLevel) :-
 2878    '$option'(autoload(Autoload), Options, false),
 2879    (   '$autoload_nesting'(CurrentLevel)
 2880    ->  AutoLevel = CurrentLevel
 2881    ;   AutoLevel = 0
 2882    ),
 2883    (   Autoload == false
 2884    ->  true
 2885    ;   NewLevel is AutoLevel + 1,
 2886	'$set_autoload_level'(NewLevel)
 2887    ).
 2888
 2889'$set_autoload_level'(New) :-
 2890    retractall('$autoload_nesting'(_)),
 2891    asserta('$autoload_nesting'(New)).
 $print_message(+Level, +Term) is det
As print_message/2, but deal with the fact that the message system might not yet be loaded.
 2899'$print_message'(Level, Term) :-
 2900    current_predicate(system:print_message/2),
 2901    !,
 2902    print_message(Level, Term).
 2903'$print_message'(warning, Term) :-
 2904    source_location(File, Line),
 2905    !,
 2906    format(user_error, 'WARNING: ~w:~w: ~p~n', [File, Line, Term]).
 2907'$print_message'(error, Term) :-
 2908    !,
 2909    source_location(File, Line),
 2910    !,
 2911    format(user_error, 'ERROR: ~w:~w: ~p~n', [File, Line, Term]).
 2912'$print_message'(_Level, _Term).
 2913
 2914'$print_message_fail'(E) :-
 2915    '$print_message'(error, E),
 2916    fail.
 $consult_file(+Path, +Module, -Action, -LoadedIn, +Options)
Called from '$do_load_file'/4 using the goal returned by '$consult_goal'/2. This means that the calling conventions must be kept synchronous with '$qload_file'/6.
 2924'$consult_file'(Absolute, Module, What, LM, Options) :-
 2925    '$current_source_module'(Module),   % same module
 2926    !,
 2927    '$consult_file_2'(Absolute, Module, What, LM, Options).
 2928'$consult_file'(Absolute, Module, What, LM, Options) :-
 2929    '$set_source_module'(OldModule, Module),
 2930    '$ifcompiling'('$qlf_start_sub_module'(Module)),
 2931    '$consult_file_2'(Absolute, Module, What, LM, Options),
 2932    '$ifcompiling'('$qlf_end_part'),
 2933    '$set_source_module'(OldModule).
 2934
 2935'$consult_file_2'(Absolute, Module, What, LM, Options) :-
 2936    '$set_source_module'(OldModule, Module),
 2937    '$load_id'(Absolute, Id, Modified, Options),
 2938    '$compile_type'(What),
 2939    '$save_lex_state'(LexState, Options),
 2940    '$set_dialect'(Options),
 2941    setup_call_cleanup(
 2942	'$start_consult'(Id, Modified),
 2943	'$load_file'(Absolute, Id, LM, Options),
 2944	'$end_consult'(Id, LexState, OldModule)).
 2945
 2946'$end_consult'(Id, LexState, OldModule) :-
 2947    '$end_consult'(Id),
 2948    '$restore_lex_state'(LexState),
 2949    '$set_source_module'(OldModule).
 2950
 2951
 2952:- create_prolog_flag(emulated_dialect, swi, [type(atom)]).
 $save_lex_state(-LexState, +Options) is det
 2956'$save_lex_state'(State, Options) :-
 2957    memberchk(scope_settings(false), Options),
 2958    !,
 2959    State = (-).
 2960'$save_lex_state'(lexstate(Style, Dialect), _) :-
 2961    '$style_check'(Style, Style),
 2962    current_prolog_flag(emulated_dialect, Dialect).
 2963
 2964'$restore_lex_state'(-) :- !.
 2965'$restore_lex_state'(lexstate(Style, Dialect)) :-
 2966    '$style_check'(_, Style),
 2967    set_prolog_flag(emulated_dialect, Dialect).
 2968
 2969'$set_dialect'(Options) :-
 2970    memberchk(dialect(Dialect), Options),
 2971    !,
 2972    '$expects_dialect'(Dialect).
 2973'$set_dialect'(_).
 2974
 2975'$load_id'(stream(Id, _, _), Id, Modified, Options) :-
 2976    !,
 2977    '$modified_id'(Id, Modified, Options).
 2978'$load_id'(Id, Id, Modified, Options) :-
 2979    '$modified_id'(Id, Modified, Options).
 2980
 2981'$modified_id'(_, Modified, Options) :-
 2982    '$option'(modified(Stamp), Options, Def),
 2983    Stamp \== Def,
 2984    !,
 2985    Modified = Stamp.
 2986'$modified_id'(Id, Modified, _) :-
 2987    catch(time_file(Id, Modified),
 2988	  error(_, _),
 2989	  fail),
 2990    !.
 2991'$modified_id'(_, 0.0, _).
 2992
 2993
 2994'$compile_type'(What) :-
 2995    '$compilation_mode'(How),
 2996    (   How == database
 2997    ->  What = compiled
 2998    ;   How == qlf
 2999    ->  What = '*qcompiled*'
 3000    ;   What = 'boot compiled'
 3001    ).
 $assert_load_context_module(+File, -Module, -Options)
Record the module a file was loaded from (see make/0). The first clause deals with loading from another file. On reload, this clause will be discarded by $start_consult/1. The second clause deals with reload from the toplevel. Here we avoid creating a duplicate dynamic (i.e., not related to a source) clause.
 3011:- dynamic
 3012    '$load_context_module'/3. 3013:- multifile
 3014    '$load_context_module'/3. 3015
 3016'$assert_load_context_module'(_, _, Options) :-
 3017    memberchk(register(false), Options),
 3018    !.
 3019'$assert_load_context_module'(File, Module, Options) :-
 3020    source_location(FromFile, Line),
 3021    !,
 3022    '$master_file'(FromFile, MasterFile),
 3023    '$check_load_non_module'(File, Module),
 3024    '$add_dialect'(Options, Options1),
 3025    '$load_ctx_options'(Options1, Options2),
 3026    '$store_admin_clause'(
 3027	system:'$load_context_module'(File, Module, Options2),
 3028	_Layout, MasterFile, FromFile:Line).
 3029'$assert_load_context_module'(File, Module, Options) :-
 3030    '$check_load_non_module'(File, Module),
 3031    '$add_dialect'(Options, Options1),
 3032    '$load_ctx_options'(Options1, Options2),
 3033    (   clause('$load_context_module'(File, Module, _), true, Ref),
 3034	\+ clause_property(Ref, file(_)),
 3035	erase(Ref)
 3036    ->  true
 3037    ;   true
 3038    ),
 3039    assertz('$load_context_module'(File, Module, Options2)).
 3040
 3041'$add_dialect'(Options0, Options) :-
 3042    current_prolog_flag(emulated_dialect, Dialect), Dialect \== swi,
 3043    !,
 3044    Options = [dialect(Dialect)|Options0].
 3045'$add_dialect'(Options, Options).
 $load_ctx_options(+Options, -CtxOptions) is det
Select the load options that determine the load semantics to perform a proper reload. Delete the others.
 3052'$load_ctx_options'(Options, CtxOptions) :-
 3053    '$load_ctx_options2'(Options, CtxOptions0),
 3054    sort(CtxOptions0, CtxOptions).
 3055
 3056'$load_ctx_options2'([], []).
 3057'$load_ctx_options2'([H|T0], [H|T]) :-
 3058    '$load_ctx_option'(H),
 3059    !,
 3060    '$load_ctx_options2'(T0, T).
 3061'$load_ctx_options2'([_|T0], T) :-
 3062    '$load_ctx_options2'(T0, T).
 3063
 3064'$load_ctx_option'(derived_from(_)).
 3065'$load_ctx_option'(dialect(_)).
 3066'$load_ctx_option'(encoding(_)).
 3067'$load_ctx_option'(imports(_)).
 3068'$load_ctx_option'(reexport(_)).
 $check_load_non_module(+File) is det
Test that a non-module file is not loaded into multiple contexts.
 3076'$check_load_non_module'(File, _) :-
 3077    '$current_module'(_, File),
 3078    !.          % File is a module file
 3079'$check_load_non_module'(File, Module) :-
 3080    '$load_context_module'(File, OldModule, _),
 3081    Module \== OldModule,
 3082    !,
 3083    format(atom(Msg),
 3084	   'Non-module file already loaded into module ~w; \c
 3085	       trying to load into ~w',
 3086	   [OldModule, Module]),
 3087    throw(error(permission_error(load, source, File),
 3088		context(load_files/2, Msg))).
 3089'$check_load_non_module'(_, _).
 $load_file(+Path, +Id, -Module, +Options)
'$load_file'/4 does the actual loading.

state(FirstTerm:boolean, Module:atom, AtEnd:atom, Stop:boolean, Id:atom, Dialect:atom)

 3102'$load_file'(Path, Id, Module, Options) :-
 3103    State = state(true, _, true, false, Id, -),
 3104    (   '$source_term'(Path, _Read, _Layout, Term, Layout,
 3105		       _Stream, Options),
 3106	'$valid_term'(Term),
 3107	(   arg(1, State, true)
 3108	->  '$first_term'(Term, Layout, Id, State, Options),
 3109	    nb_setarg(1, State, false)
 3110	;   '$compile_term'(Term, Layout, Id, Options)
 3111	),
 3112	arg(4, State, true)
 3113    ;   '$fixup_reconsult'(Id),
 3114	'$end_load_file'(State)
 3115    ),
 3116    !,
 3117    arg(2, State, Module).
 3118
 3119'$valid_term'(Var) :-
 3120    var(Var),
 3121    !,
 3122    print_message(error, error(instantiation_error, _)).
 3123'$valid_term'(Term) :-
 3124    Term \== [].
 3125
 3126'$end_load_file'(State) :-
 3127    arg(1, State, true),           % empty file
 3128    !,
 3129    nb_setarg(2, State, Module),
 3130    arg(5, State, Id),
 3131    '$current_source_module'(Module),
 3132    '$ifcompiling'('$qlf_start_file'(Id)),
 3133    '$ifcompiling'('$qlf_end_part').
 3134'$end_load_file'(State) :-
 3135    arg(3, State, End),
 3136    '$end_load_file'(End, State).
 3137
 3138'$end_load_file'(true, _).
 3139'$end_load_file'(end_module, State) :-
 3140    arg(2, State, Module),
 3141    '$check_export'(Module),
 3142    '$ifcompiling'('$qlf_end_part').
 3143'$end_load_file'(end_non_module, _State) :-
 3144    '$ifcompiling'('$qlf_end_part').
 3145
 3146
 3147'$first_term'(?-(Directive), Layout, Id, State, Options) :-
 3148    !,
 3149    '$first_term'(:-(Directive), Layout, Id, State, Options).
 3150'$first_term'(:-(Directive), _Layout, Id, State, Options) :-
 3151    nonvar(Directive),
 3152    (   (   Directive = module(Name, Public)
 3153	->  Imports = []
 3154	;   Directive = module(Name, Public, Imports)
 3155	)
 3156    ->  !,
 3157	'$module_name'(Name, Id, Module, Options),
 3158	'$start_module'(Module, Public, State, Options),
 3159	'$module3'(Imports)
 3160    ;   Directive = expects_dialect(Dialect)
 3161    ->  !,
 3162	'$set_dialect'(Dialect, State),
 3163	fail                        % Still consider next term as first
 3164    ).
 3165'$first_term'(Term, Layout, Id, State, Options) :-
 3166    '$start_non_module'(Id, Term, State, Options),
 3167    '$compile_term'(Term, Layout, Id, Options).
 $compile_term(+Term, +Layout, +SrcId, +Options) is det
 $compile_term(+Term, +Layout, +SrcId, +SrcLoc, +Options) is det
Distinguish between directives and normal clauses.
 3174'$compile_term'(Term, Layout, SrcId, Options) :-
 3175    '$compile_term'(Term, Layout, SrcId, -, Options).
 3176
 3177'$compile_term'(Var, _Layout, _Id, _SrcLoc, _Options) :-
 3178    var(Var),
 3179    !,
 3180    '$instantiation_error'(Var).
 3181'$compile_term'((?-Directive), _Layout, Id, _SrcLoc, Options) :-
 3182    !,
 3183    '$execute_directive'(Directive, Id, Options).
 3184'$compile_term'((:-Directive), _Layout, Id, _SrcLoc, Options) :-
 3185    !,
 3186    '$execute_directive'(Directive, Id, Options).
 3187'$compile_term'('$source_location'(File, Line):Term,
 3188		Layout, Id, _SrcLoc, Options) :-
 3189    !,
 3190    '$compile_term'(Term, Layout, Id, File:Line, Options).
 3191'$compile_term'(Clause, Layout, Id, SrcLoc, _Options) :-
 3192    E = error(_,_),
 3193    catch('$store_clause'(Clause, Layout, Id, SrcLoc), E,
 3194	  '$print_message'(error, E)).
 3195
 3196'$start_non_module'(_Id, Term, _State, Options) :-
 3197    '$option'(must_be_module(true), Options, false),
 3198    !,
 3199    '$domain_error'(module_header, Term).
 3200'$start_non_module'(Id, _Term, State, _Options) :-
 3201    '$current_source_module'(Module),
 3202    '$ifcompiling'('$qlf_start_file'(Id)),
 3203    '$qset_dialect'(State),
 3204    nb_setarg(2, State, Module),
 3205    nb_setarg(3, State, end_non_module).
 $set_dialect(+Dialect, +State)
Sets the expected dialect. This is difficult if we are compiling a .qlf file using qcompile/1 because the file is already open, while we are looking for the first term to decide wether this is a module or not. We save the dialect and set it after opening the file or module.

Note that expects_dialect/1 itself may be autoloaded from the library.

 3218'$set_dialect'(Dialect, State) :-
 3219    '$compilation_mode'(qlf, database),
 3220    !,
 3221    '$expects_dialect'(Dialect),
 3222    '$compilation_mode'(_, qlf),
 3223    nb_setarg(6, State, Dialect).
 3224'$set_dialect'(Dialect, _) :-
 3225    '$expects_dialect'(Dialect).
 3226
 3227'$qset_dialect'(State) :-
 3228    '$compilation_mode'(qlf),
 3229    arg(6, State, Dialect), Dialect \== (-),
 3230    !,
 3231    '$add_directive_wic'('$expects_dialect'(Dialect)).
 3232'$qset_dialect'(_).
 3233
 3234'$expects_dialect'(Dialect) :-
 3235    Dialect == swi,
 3236    !,
 3237    set_prolog_flag(emulated_dialect, Dialect).
 3238'$expects_dialect'(Dialect) :-
 3239    current_predicate(expects_dialect/1),
 3240    !,
 3241    expects_dialect(Dialect).
 3242'$expects_dialect'(Dialect) :-
 3243    use_module(library(dialect), [expects_dialect/1]),
 3244    expects_dialect(Dialect).
 3245
 3246
 3247		 /*******************************
 3248		 *           MODULES            *
 3249		 *******************************/
 3250
 3251'$start_module'(Module, _Public, State, _Options) :-
 3252    '$current_module'(Module, OldFile),
 3253    source_location(File, _Line),
 3254    OldFile \== File, OldFile \== [],
 3255    same_file(OldFile, File),
 3256    !,
 3257    nb_setarg(2, State, Module),
 3258    nb_setarg(4, State, true).      % Stop processing
 3259'$start_module'(Module, Public, State, Options) :-
 3260    arg(5, State, File),
 3261    nb_setarg(2, State, Module),
 3262    source_location(_File, Line),
 3263    '$option'(redefine_module(Action), Options, false),
 3264    '$module_class'(File, Class, Super),
 3265    '$reset_dialect'(File, Class),
 3266    '$redefine_module'(Module, File, Action),
 3267    '$declare_module'(Module, Class, Super, File, Line, false),
 3268    '$export_list'(Public, Module, Ops),
 3269    '$ifcompiling'('$qlf_start_module'(Module)),
 3270    '$export_ops'(Ops, Module, File),
 3271    '$qset_dialect'(State),
 3272    nb_setarg(3, State, end_module).
 $reset_dialect(+File, +Class) is det
Load .pl files from the SWI-Prolog distribution always in swi dialect.
 3279'$reset_dialect'(File, library) :-
 3280    file_name_extension(_, pl, File),
 3281    !,
 3282    set_prolog_flag(emulated_dialect, swi).
 3283'$reset_dialect'(_, _).
 $module3(+Spec) is det
Handle the 3th argument of a module declartion.
 3290'$module3'(Var) :-
 3291    var(Var),
 3292    !,
 3293    '$instantiation_error'(Var).
 3294'$module3'([]) :- !.
 3295'$module3'([H|T]) :-
 3296    !,
 3297    '$module3'(H),
 3298    '$module3'(T).
 3299'$module3'(Id) :-
 3300    use_module(library(dialect/Id)).
 $module_name(?Name, +Id, -Module, +Options) is semidet
Determine the module name. There are some cases:
 3314'$module_name'(_, _, Module, Options) :-
 3315    '$option'(module(Module), Options),
 3316    !,
 3317    '$current_source_module'(Context),
 3318    Context \== Module.                     % cause '$first_term'/5 to fail.
 3319'$module_name'(Var, Id, Module, Options) :-
 3320    var(Var),
 3321    !,
 3322    file_base_name(Id, File),
 3323    file_name_extension(Var, _, File),
 3324    '$module_name'(Var, Id, Module, Options).
 3325'$module_name'(Reserved, _, _, _) :-
 3326    '$reserved_module'(Reserved),
 3327    !,
 3328    throw(error(permission_error(load, module, Reserved), _)).
 3329'$module_name'(Module, _Id, Module, _).
 3330
 3331
 3332'$reserved_module'(system).
 3333'$reserved_module'(user).
 $redefine_module(+Module, +File, -Redefine)
 3338'$redefine_module'(_Module, _, false) :- !.
 3339'$redefine_module'(Module, File, true) :-
 3340    !,
 3341    (   module_property(Module, file(OldFile)),
 3342	File \== OldFile
 3343    ->  unload_file(OldFile)
 3344    ;   true
 3345    ).
 3346'$redefine_module'(Module, File, ask) :-
 3347    (   stream_property(user_input, tty(true)),
 3348	module_property(Module, file(OldFile)),
 3349	File \== OldFile,
 3350	'$rdef_response'(Module, OldFile, File, true)
 3351    ->  '$redefine_module'(Module, File, true)
 3352    ;   true
 3353    ).
 3354
 3355'$rdef_response'(Module, OldFile, File, Ok) :-
 3356    repeat,
 3357    print_message(query, redefine_module(Module, OldFile, File)),
 3358    get_single_char(Char),
 3359    '$rdef_response'(Char, Ok0),
 3360    !,
 3361    Ok = Ok0.
 3362
 3363'$rdef_response'(Char, true) :-
 3364    memberchk(Char, `yY`),
 3365    format(user_error, 'yes~n', []).
 3366'$rdef_response'(Char, false) :-
 3367    memberchk(Char, `nN`),
 3368    format(user_error, 'no~n', []).
 3369'$rdef_response'(Char, _) :-
 3370    memberchk(Char, `a`),
 3371    format(user_error, 'abort~n', []),
 3372    abort.
 3373'$rdef_response'(_, _) :-
 3374    print_message(help, redefine_module_reply),
 3375    fail.
 $module_class(+File, -Class, -Super) is det
Determine the file class and initial module from which File inherits. All boot and library modules as well as the -F script files inherit from system, while all normal user modules inherit from user.
 3385'$module_class'(File, Class, system) :-
 3386    current_prolog_flag(home, Home),
 3387    sub_atom(File, 0, Len, _, Home),
 3388    (   sub_atom(File, Len, _, _, '/boot/')
 3389    ->  !, Class = system
 3390    ;   '$lib_prefix'(Prefix),
 3391	sub_atom(File, Len, _, _, Prefix)
 3392    ->  !, Class = library
 3393    ;   file_directory_name(File, Home),
 3394	file_name_extension(_, rc, File)
 3395    ->  !, Class = library
 3396    ).
 3397'$module_class'(_, user, user).
 3398
 3399'$lib_prefix'('/library').
 3400'$lib_prefix'('/xpce/prolog/').
 3401
 3402'$check_export'(Module) :-
 3403    '$undefined_export'(Module, UndefList),
 3404    (   '$member'(Undef, UndefList),
 3405	strip_module(Undef, _, Local),
 3406	print_message(error,
 3407		      undefined_export(Module, Local)),
 3408	fail
 3409    ;   true
 3410    ).
 $import_list(+TargetModule, +FromModule, +Import, +Reexport) is det
Import from FromModule to TargetModule. Import is one of all, a list of optionally mapped predicate indicators or a term except(Import).
 3419'$import_list'(_, _, Var, _) :-
 3420    var(Var),
 3421    !,
 3422    throw(error(instantitation_error, _)).
 3423'$import_list'(Target, Source, all, Reexport) :-
 3424    !,
 3425    '$exported_ops'(Source, Import, Predicates),
 3426    '$module_property'(Source, exports(Predicates)),
 3427    '$import_all'(Import, Target, Source, Reexport, weak).
 3428'$import_list'(Target, Source, except(Spec), Reexport) :-
 3429    !,
 3430    '$exported_ops'(Source, Export, Predicates),
 3431    '$module_property'(Source, exports(Predicates)),
 3432    (   is_list(Spec)
 3433    ->  true
 3434    ;   throw(error(type_error(list, Spec), _))
 3435    ),
 3436    '$import_except'(Spec, Export, Import),
 3437    '$import_all'(Import, Target, Source, Reexport, weak).
 3438'$import_list'(Target, Source, Import, Reexport) :-
 3439    !,
 3440    is_list(Import),
 3441    !,
 3442    '$import_all'(Import, Target, Source, Reexport, strong).
 3443'$import_list'(_, _, Import, _) :-
 3444    throw(error(type_error(import_specifier, Import))).
 3445
 3446
 3447'$import_except'([], List, List).
 3448'$import_except'([H|T], List0, List) :-
 3449    '$import_except_1'(H, List0, List1),
 3450    '$import_except'(T, List1, List).
 3451
 3452'$import_except_1'(Var, _, _) :-
 3453    var(Var),
 3454    !,
 3455    throw(error(instantitation_error, _)).
 3456'$import_except_1'(PI as N, List0, List) :-
 3457    '$pi'(PI), atom(N),
 3458    !,
 3459    '$canonical_pi'(PI, CPI),
 3460    '$import_as'(CPI, N, List0, List).
 3461'$import_except_1'(op(P,A,N), List0, List) :-
 3462    !,
 3463    '$remove_ops'(List0, op(P,A,N), List).
 3464'$import_except_1'(PI, List0, List) :-
 3465    '$pi'(PI),
 3466    !,
 3467    '$canonical_pi'(PI, CPI),
 3468    '$select'(P, List0, List),
 3469    '$canonical_pi'(CPI, P),
 3470    !.
 3471'$import_except_1'(Except, _, _) :-
 3472    throw(error(type_error(import_specifier, Except), _)).
 3473
 3474'$import_as'(CPI, N, [PI2|T], [CPI as N|T]) :-
 3475    '$canonical_pi'(PI2, CPI),
 3476    !.
 3477'$import_as'(PI, N, [H|T0], [H|T]) :-
 3478    !,
 3479    '$import_as'(PI, N, T0, T).
 3480'$import_as'(PI, _, _, _) :-
 3481    throw(error(existence_error(export, PI), _)).
 3482
 3483'$pi'(N/A) :- atom(N), integer(A), !.
 3484'$pi'(N//A) :- atom(N), integer(A).
 3485
 3486'$canonical_pi'(N//A0, N/A) :-
 3487    A is A0 + 2.
 3488'$canonical_pi'(PI, PI).
 3489
 3490'$remove_ops'([], _, []).
 3491'$remove_ops'([Op|T0], Pattern, T) :-
 3492    subsumes_term(Pattern, Op),
 3493    !,
 3494    '$remove_ops'(T0, Pattern, T).
 3495'$remove_ops'([H|T0], Pattern, [H|T]) :-
 3496    '$remove_ops'(T0, Pattern, T).
 $import_all(+Import, +Context, +Source, +Reexport, +Strength)
 3501'$import_all'(Import, Context, Source, Reexport, Strength) :-
 3502    '$import_all2'(Import, Context, Source, Imported, ImpOps, Strength),
 3503    (   Reexport == true,
 3504	(   '$list_to_conj'(Imported, Conj)
 3505	->  export(Context:Conj),
 3506	    '$ifcompiling'('$add_directive_wic'(export(Context:Conj)))
 3507	;   true
 3508	),
 3509	source_location(File, _Line),
 3510	'$export_ops'(ImpOps, Context, File)
 3511    ;   true
 3512    ).
 $import_all2(+Imports, +Context, +Source, -Imported, -ImpOps, +Strength)
 3516'$import_all2'([], _, _, [], [], _).
 3517'$import_all2'([PI as NewName|Rest], Context, Source,
 3518	       [NewName/Arity|Imported], ImpOps, Strength) :-
 3519    !,
 3520    '$canonical_pi'(PI, Name/Arity),
 3521    length(Args, Arity),
 3522    Head =.. [Name|Args],
 3523    NewHead =.. [NewName|Args],
 3524    (   '$get_predicate_attribute'(Source:Head, transparent, 1)
 3525    ->  '$set_predicate_attribute'(Context:NewHead, transparent, true)
 3526    ;   true
 3527    ),
 3528    (   source_location(File, Line)
 3529    ->  E = error(_,_),
 3530	catch('$store_admin_clause'((NewHead :- Source:Head),
 3531				    _Layout, File, File:Line),
 3532	      E, '$print_message'(error, E))
 3533    ;   assertz((NewHead :- !, Source:Head)) % ! avoids problems with
 3534    ),                                       % duplicate load
 3535    '$import_all2'(Rest, Context, Source, Imported, ImpOps, Strength).
 3536'$import_all2'([op(P,A,N)|Rest], Context, Source, Imported,
 3537	       [op(P,A,N)|ImpOps], Strength) :-
 3538    !,
 3539    '$import_ops'(Context, Source, op(P,A,N)),
 3540    '$import_all2'(Rest, Context, Source, Imported, ImpOps, Strength).
 3541'$import_all2'([Pred|Rest], Context, Source, [Pred|Imported], ImpOps, Strength) :-
 3542    Error = error(_,_),
 3543    catch(Context:'$import'(Source:Pred, Strength), Error,
 3544	  print_message(error, Error)),
 3545    '$ifcompiling'('$import_wic'(Source, Pred, Strength)),
 3546    '$import_all2'(Rest, Context, Source, Imported, ImpOps, Strength).
 3547
 3548
 3549'$list_to_conj'([One], One) :- !.
 3550'$list_to_conj'([H|T], (H,Rest)) :-
 3551    '$list_to_conj'(T, Rest).
 $exported_ops(+Module, -Ops, ?Tail) is det
Ops is a list of op(P,A,N) terms representing the operators exported from Module.
 3558'$exported_ops'(Module, Ops, Tail) :-
 3559    '$c_current_predicate'(_, Module:'$exported_op'(_,_,_)),
 3560    !,
 3561    findall(op(P,A,N), Module:'$exported_op'(P,A,N), Ops, Tail).
 3562'$exported_ops'(_, Ops, Ops).
 3563
 3564'$exported_op'(Module, P, A, N) :-
 3565    '$c_current_predicate'(_, Module:'$exported_op'(_,_,_)),
 3566    Module:'$exported_op'(P, A, N).
 $import_ops(+Target, +Source, +Pattern)
Import the operators export from Source into the module table of Target. We only import operators that unify with Pattern.
 3573'$import_ops'(To, From, Pattern) :-
 3574    ground(Pattern),
 3575    !,
 3576    Pattern = op(P,A,N),
 3577    op(P,A,To:N),
 3578    (   '$exported_op'(From, P, A, N)
 3579    ->  true
 3580    ;   print_message(warning, no_exported_op(From, Pattern))
 3581    ).
 3582'$import_ops'(To, From, Pattern) :-
 3583    (   '$exported_op'(From, Pri, Assoc, Name),
 3584	Pattern = op(Pri, Assoc, Name),
 3585	op(Pri, Assoc, To:Name),
 3586	fail
 3587    ;   true
 3588    ).
 $export_list(+Declarations, +Module, -Ops)
Handle the export list of the module declaration for Module associated to File.
 3596'$export_list'(Decls, Module, Ops) :-
 3597    is_list(Decls),
 3598    !,
 3599    '$do_export_list'(Decls, Module, Ops).
 3600'$export_list'(Decls, _, _) :-
 3601    var(Decls),
 3602    throw(error(instantiation_error, _)).
 3603'$export_list'(Decls, _, _) :-
 3604    throw(error(type_error(list, Decls), _)).
 3605
 3606'$do_export_list'([], _, []) :- !.
 3607'$do_export_list'([H|T], Module, Ops) :-
 3608    !,
 3609    E = error(_,_),
 3610    catch('$export1'(H, Module, Ops, Ops1),
 3611	  E, ('$print_message'(error, E), Ops = Ops1)),
 3612    '$do_export_list'(T, Module, Ops1).
 3613
 3614'$export1'(Var, _, _, _) :-
 3615    var(Var),
 3616    !,
 3617    throw(error(instantiation_error, _)).
 3618'$export1'(Op, _, [Op|T], T) :-
 3619    Op = op(_,_,_),
 3620    !.
 3621'$export1'(PI0, Module, Ops, Ops) :-
 3622    strip_module(Module:PI0, M, PI),
 3623    (   PI = (_//_)
 3624    ->  non_terminal(M:PI)
 3625    ;   true
 3626    ),
 3627    export(M:PI).
 3628
 3629'$export_ops'([op(Pri, Assoc, Name)|T], Module, File) :-
 3630    E = error(_,_),
 3631    catch(( '$execute_directive'(op(Pri, Assoc, Module:Name), File, []),
 3632	    '$export_op'(Pri, Assoc, Name, Module, File)
 3633	  ),
 3634	  E, '$print_message'(error, E)),
 3635    '$export_ops'(T, Module, File).
 3636'$export_ops'([], _, _).
 3637
 3638'$export_op'(Pri, Assoc, Name, Module, File) :-
 3639    (   '$get_predicate_attribute'(Module:'$exported_op'(_,_,_), defined, 1)
 3640    ->  true
 3641    ;   '$execute_directive'(discontiguous(Module:'$exported_op'/3), File, [])
 3642    ),
 3643    '$store_admin_clause'('$exported_op'(Pri, Assoc, Name), _Layout, File, -).
 $execute_directive(:Goal, +File, +Options) is det
Execute the argument of :- or ?- while loading a file.
 3649'$execute_directive'(Var, _F, _Options) :-
 3650    var(Var),
 3651    '$instantiation_error'(Var).
 3652'$execute_directive'(encoding(Encoding), _F, _Options) :-
 3653    !,
 3654    (   '$load_input'(_F, S)
 3655    ->  set_stream(S, encoding(Encoding))
 3656    ).
 3657'$execute_directive'(Goal, _, Options) :-
 3658    \+ '$compilation_mode'(database),
 3659    !,
 3660    '$add_directive_wic2'(Goal, Type, Options),
 3661    (   Type == call                % suspend compiling into .qlf file
 3662    ->  '$compilation_mode'(Old, database),
 3663	setup_call_cleanup(
 3664	    '$directive_mode'(OldDir, Old),
 3665	    '$execute_directive_3'(Goal),
 3666	    ( '$set_compilation_mode'(Old),
 3667	      '$set_directive_mode'(OldDir)
 3668	    ))
 3669    ;   '$execute_directive_3'(Goal)
 3670    ).
 3671'$execute_directive'(Goal, _, _Options) :-
 3672    '$execute_directive_3'(Goal).
 3673
 3674'$execute_directive_3'(Goal) :-
 3675    '$current_source_module'(Module),
 3676    '$valid_directive'(Module:Goal),
 3677    !,
 3678    (   '$pattr_directive'(Goal, Module)
 3679    ->  true
 3680    ;   Term = error(_,_),
 3681	catch(Module:Goal, Term, '$exception_in_directive'(Term))
 3682    ->  true
 3683    ;   '$print_message'(warning, goal_failed(directive, Module:Goal)),
 3684	fail
 3685    ).
 3686'$execute_directive_3'(_).
 $valid_directive(:Directive) is det
If the flag sandboxed_load is true, this calls prolog:sandbox_allowed_directive/1. This call can deny execution of the directive by throwing an exception.
 3695:- multifile prolog:sandbox_allowed_directive/1. 3696:- multifile prolog:sandbox_allowed_clause/1. 3697:- meta_predicate '$valid_directive'(:). 3698
 3699'$valid_directive'(_) :-
 3700    current_prolog_flag(sandboxed_load, false),
 3701    !.
 3702'$valid_directive'(Goal) :-
 3703    Error = error(Formal, _),
 3704    catch(prolog:sandbox_allowed_directive(Goal), Error, true),
 3705    !,
 3706    (   var(Formal)
 3707    ->  true
 3708    ;   print_message(error, Error),
 3709	fail
 3710    ).
 3711'$valid_directive'(Goal) :-
 3712    print_message(error,
 3713		  error(permission_error(execute,
 3714					 sandboxed_directive,
 3715					 Goal), _)),
 3716    fail.
 3717
 3718'$exception_in_directive'(Term) :-
 3719    '$print_message'(error, Term),
 3720    fail.
 $add_directive_wic2(+Directive, -Type, +Options) is det
Classify Directive as one of load or call. Add a call directive to the QLF file. load directives continue the compilation into the QLF file.
 3728'$add_directive_wic2'(Goal, Type, Options) :-
 3729    '$common_goal_type'(Goal, Type, Options),
 3730    !,
 3731    (   Type == load
 3732    ->  true
 3733    ;   '$current_source_module'(Module),
 3734	'$add_directive_wic'(Module:Goal)
 3735    ).
 3736'$add_directive_wic2'(Goal, _, _) :-
 3737    (   '$compilation_mode'(qlf)    % no problem for qlf files
 3738    ->  true
 3739    ;   print_message(error, mixed_directive(Goal))
 3740    ).
 $common_goal_type(+Directive, -Type, +Options) is semidet
True when all subgoals of Directive must be handled using load or call.
 3747'$common_goal_type'((A,B), Type, Options) :-
 3748    !,
 3749    '$common_goal_type'(A, Type, Options),
 3750    '$common_goal_type'(B, Type, Options).
 3751'$common_goal_type'((A;B), Type, Options) :-
 3752    !,
 3753    '$common_goal_type'(A, Type, Options),
 3754    '$common_goal_type'(B, Type, Options).
 3755'$common_goal_type'((A->B), Type, Options) :-
 3756    !,
 3757    '$common_goal_type'(A, Type, Options),
 3758    '$common_goal_type'(B, Type, Options).
 3759'$common_goal_type'(Goal, Type, Options) :-
 3760    '$goal_type'(Goal, Type, Options).
 3761
 3762'$goal_type'(Goal, Type, Options) :-
 3763    (   '$load_goal'(Goal, Options)
 3764    ->  Type = load
 3765    ;   Type = call
 3766    ).
 3767
 3768:- thread_local
 3769    '$qlf':qinclude/1. 3770
 3771'$load_goal'([_|_], _).
 3772'$load_goal'(consult(_), _).
 3773'$load_goal'(load_files(_), _).
 3774'$load_goal'(load_files(_,Options), _) :-
 3775    memberchk(qcompile(QlfMode), Options),
 3776    '$qlf_part_mode'(QlfMode).
 3777'$load_goal'(ensure_loaded(_), _) :- '$compilation_mode'(wic).
 3778'$load_goal'(use_module(_), _)    :- '$compilation_mode'(wic).
 3779'$load_goal'(use_module(_, _), _) :- '$compilation_mode'(wic).
 3780'$load_goal'(reexport(_), _)      :- '$compilation_mode'(wic).
 3781'$load_goal'(reexport(_, _), _)   :- '$compilation_mode'(wic).
 3782'$load_goal'(Goal, _Options) :-
 3783    '$qlf':qinclude(user),
 3784    '$load_goal_file'(Goal, File),
 3785    '$all_user_files'(File).
 3786
 3787
 3788'$load_goal_file'(load_files(F), F).
 3789'$load_goal_file'(load_files(F, _), F).
 3790'$load_goal_file'(ensure_loaded(F), F).
 3791'$load_goal_file'(use_module(F), F).
 3792'$load_goal_file'(use_module(F, _), F).
 3793'$load_goal_file'(reexport(F), F).
 3794'$load_goal_file'(reexport(F, _), F).
 3795
 3796'$all_user_files'([]) :-
 3797    !.
 3798'$all_user_files'([H|T]) :-
 3799    !,
 3800    '$is_user_file'(H),
 3801    '$all_user_files'(T).
 3802'$all_user_files'(F) :-
 3803    ground(F),
 3804    '$is_user_file'(F).
 3805
 3806'$is_user_file'(File) :-
 3807    absolute_file_name(File, Path,
 3808		       [ file_type(prolog),
 3809			 access(read)
 3810		       ]),
 3811    '$module_class'(Path, user, _).
 3812
 3813'$qlf_part_mode'(part).
 3814'$qlf_part_mode'(true).                 % compatibility
 3815
 3816
 3817		/********************************
 3818		*        COMPILE A CLAUSE       *
 3819		*********************************/
 $store_admin_clause(+Clause, ?Layout, +Owner, +SrcLoc) is det
Store a clause into the database for administrative purposes. This bypasses sanity checking.
 3826'$store_admin_clause'(Clause, Layout, Owner, SrcLoc) :-
 3827    Owner \== (-),
 3828    !,
 3829    setup_call_cleanup(
 3830	'$start_aux'(Owner, Context),
 3831	'$store_admin_clause2'(Clause, Layout, Owner, SrcLoc),
 3832	'$end_aux'(Owner, Context)).
 3833'$store_admin_clause'(Clause, Layout, File, SrcLoc) :-
 3834    '$store_admin_clause2'(Clause, Layout, File, SrcLoc).
 3835
 3836'$store_admin_clause2'(Clause, _Layout, File, SrcLoc) :-
 3837    (   '$compilation_mode'(database)
 3838    ->  '$record_clause'(Clause, File, SrcLoc)
 3839    ;   '$record_clause'(Clause, File, SrcLoc, Ref),
 3840	'$qlf_assert_clause'(Ref, development)
 3841    ).
 $store_clause(+Clause, ?Layout, +Owner, +SrcLoc) is det
Store a clause into the database.
Arguments:
Owner- is the file-id that owns the clause
SrcLoc- is the file:line term where the clause originates from.
 3851'$store_clause'((_, _), _, _, _) :-
 3852    !,
 3853    print_message(error, cannot_redefine_comma),
 3854    fail.
 3855'$store_clause'((Pre => Body), _Layout, File, SrcLoc) :-
 3856    nonvar(Pre),
 3857    Pre = (Head,Cond),
 3858    !,
 3859    (   '$is_true'(Cond), current_prolog_flag(optimise, true)
 3860    ->  '$store_clause'((Head=>Body), _Layout, File, SrcLoc)
 3861    ;   '$store_clause'(?=>(Head,(Cond,!,Body)), _Layout, File, SrcLoc)
 3862    ).
 3863'$store_clause'(Clause, _Layout, File, SrcLoc) :-
 3864    '$valid_clause'(Clause),
 3865    !,
 3866    (   '$compilation_mode'(database)
 3867    ->  '$record_clause'(Clause, File, SrcLoc)
 3868    ;   '$record_clause'(Clause, File, SrcLoc, Ref),
 3869	'$qlf_assert_clause'(Ref, development)
 3870    ).
 3871
 3872'$is_true'(true)  => true.
 3873'$is_true'((A,B)) => '$is_true'(A), '$is_true'(B).
 3874'$is_true'(_)     => fail.
 3875
 3876'$valid_clause'(_) :-
 3877    current_prolog_flag(sandboxed_load, false),
 3878    !.
 3879'$valid_clause'(Clause) :-
 3880    \+ '$cross_module_clause'(Clause),
 3881    !.
 3882'$valid_clause'(Clause) :-
 3883    Error = error(Formal, _),
 3884    catch(prolog:sandbox_allowed_clause(Clause), Error, true),
 3885    !,
 3886    (   var(Formal)
 3887    ->  true
 3888    ;   print_message(error, Error),
 3889	fail
 3890    ).
 3891'$valid_clause'(Clause) :-
 3892    print_message(error,
 3893		  error(permission_error(assert,
 3894					 sandboxed_clause,
 3895					 Clause), _)),
 3896    fail.
 3897
 3898'$cross_module_clause'(Clause) :-
 3899    '$head_module'(Clause, Module),
 3900    \+ '$current_source_module'(Module).
 3901
 3902'$head_module'(Var, _) :-
 3903    var(Var), !, fail.
 3904'$head_module'((Head :- _), Module) :-
 3905    '$head_module'(Head, Module).
 3906'$head_module'(Module:_, Module).
 3907
 3908'$clause_source'('$source_location'(File,Line):Clause, Clause, File:Line) :- !.
 3909'$clause_source'(Clause, Clause, -).
 $store_clause(+Term, +Id) is det
This interface is used by PlDoc (and who knows). Kept for to avoid compatibility issues.
 3916:- public
 3917    '$store_clause'/2. 3918
 3919'$store_clause'(Term, Id) :-
 3920    '$clause_source'(Term, Clause, SrcLoc),
 3921    '$store_clause'(Clause, _, Id, SrcLoc).
 compile_aux_clauses(+Clauses) is det
Compile clauses given the current source location but do not change the notion of the current procedure such that discontiguous warnings are not issued. The clauses are associated with the current file and therefore wiped out if the file is reloaded.

If the cross-referencer is active, we should not (re-)assert the clauses. Actually, we should make them known to the cross-referencer. How do we do that? Maybe we need a different API, such as in:

expand_term_aux(Goal, NewGoal, Clauses)
To be done
- Deal with source code layout?
 3942compile_aux_clauses(_Clauses) :-
 3943    current_prolog_flag(xref, true),
 3944    !.
 3945compile_aux_clauses(Clauses) :-
 3946    source_location(File, _Line),
 3947    '$compile_aux_clauses'(Clauses, File).
 3948
 3949'$compile_aux_clauses'(Clauses, File) :-
 3950    setup_call_cleanup(
 3951	'$start_aux'(File, Context),
 3952	'$store_aux_clauses'(Clauses, File),
 3953	'$end_aux'(File, Context)).
 3954
 3955'$store_aux_clauses'(Clauses, File) :-
 3956    is_list(Clauses),
 3957    !,
 3958    forall('$member'(C,Clauses),
 3959	   '$compile_term'(C, _Layout, File, [])).
 3960'$store_aux_clauses'(Clause, File) :-
 3961    '$compile_term'(Clause, _Layout, File, []).
 3962
 3963
 3964		 /*******************************
 3965		 *            STAGING		*
 3966		 *******************************/
 $stage_file(+Target, -Stage) is det
 $install_staged_file(+Catcher, +Staged, +Target, +OnError)
Create files using staging, where we first write a temporary file and move it to Target if the file was created successfully. This provides an atomic transition, preventing customers from reading an incomplete file.
 3976'$stage_file'(Target, Stage) :-
 3977    file_directory_name(Target, Dir),
 3978    file_base_name(Target, File),
 3979    current_prolog_flag(pid, Pid),
 3980    format(atom(Stage), '~w/.~w.~d', [Dir,File,Pid]).
 3981
 3982'$install_staged_file'(exit, Staged, Target, error) :-
 3983    !,
 3984    rename_file(Staged, Target).
 3985'$install_staged_file'(exit, Staged, Target, OnError) :-
 3986    !,
 3987    InstallError = error(_,_),
 3988    catch(rename_file(Staged, Target),
 3989	  InstallError,
 3990	  '$install_staged_error'(OnError, InstallError, Staged, Target)).
 3991'$install_staged_file'(_, Staged, _, _OnError) :-
 3992    E = error(_,_),
 3993    catch(delete_file(Staged), E, true).
 3994
 3995'$install_staged_error'(OnError, Error, Staged, _Target) :-
 3996    E = error(_,_),
 3997    catch(delete_file(Staged), E, true),
 3998    (   OnError = silent
 3999    ->  true
 4000    ;   OnError = fail
 4001    ->  fail
 4002    ;   print_message(warning, Error)
 4003    ).
 4004
 4005
 4006		 /*******************************
 4007		 *             READING          *
 4008		 *******************************/
 4009
 4010:- multifile
 4011    prolog:comment_hook/3.                  % hook for read_clause/3
 4012
 4013
 4014		 /*******************************
 4015		 *       FOREIGN INTERFACE      *
 4016		 *******************************/
 4017
 4018%       call-back from PL_register_foreign().  First argument is the module
 4019%       into which the foreign predicate is loaded and second is a term
 4020%       describing the arguments.
 4021
 4022:- dynamic
 4023    '$foreign_registered'/2. 4024
 4025		 /*******************************
 4026		 *   TEMPORARY TERM EXPANSION   *
 4027		 *******************************/
 4028
 4029% Provide temporary definitions for the boot-loader.  These are replaced
 4030% by the real thing in load.pl
 4031
 4032:- dynamic
 4033    '$expand_goal'/2,
 4034    '$expand_term'/4. 4035
 4036'$expand_goal'(In, In).
 4037'$expand_term'(In, Layout, In, Layout).
 4038
 4039
 4040		 /*******************************
 4041		 *         TYPE SUPPORT         *
 4042		 *******************************/
 4043
 4044'$type_error'(Type, Value) :-
 4045    (   var(Value)
 4046    ->  throw(error(instantiation_error, _))
 4047    ;   throw(error(type_error(Type, Value), _))
 4048    ).
 4049
 4050'$domain_error'(Type, Value) :-
 4051    throw(error(domain_error(Type, Value), _)).
 4052
 4053'$existence_error'(Type, Object) :-
 4054    throw(error(existence_error(Type, Object), _)).
 4055
 4056'$permission_error'(Action, Type, Term) :-
 4057    throw(error(permission_error(Action, Type, Term), _)).
 4058
 4059'$instantiation_error'(_Var) :-
 4060    throw(error(instantiation_error, _)).
 4061
 4062'$uninstantiation_error'(NonVar) :-
 4063    throw(error(uninstantiation_error(NonVar), _)).
 4064
 4065'$must_be'(list, X) :- !,
 4066    '$skip_list'(_, X, Tail),
 4067    (   Tail == []
 4068    ->  true
 4069    ;   '$type_error'(list, Tail)
 4070    ).
 4071'$must_be'(options, X) :- !,
 4072    (   '$is_options'(X)
 4073    ->  true
 4074    ;   '$type_error'(options, X)
 4075    ).
 4076'$must_be'(atom, X) :- !,
 4077    (   atom(X)
 4078    ->  true
 4079    ;   '$type_error'(atom, X)
 4080    ).
 4081'$must_be'(integer, X) :- !,
 4082    (   integer(X)
 4083    ->  true
 4084    ;   '$type_error'(integer, X)
 4085    ).
 4086'$must_be'(between(Low,High), X) :- !,
 4087    (   integer(X)
 4088    ->  (   between(Low, High, X)
 4089	->  true
 4090	;   '$domain_error'(between(Low,High), X)
 4091	)
 4092    ;   '$type_error'(integer, X)
 4093    ).
 4094'$must_be'(callable, X) :- !,
 4095    (   callable(X)
 4096    ->  true
 4097    ;   '$type_error'(callable, X)
 4098    ).
 4099'$must_be'(acyclic, X) :- !,
 4100    (   acyclic_term(X)
 4101    ->  true
 4102    ;   '$domain_error'(acyclic_term, X)
 4103    ).
 4104'$must_be'(oneof(Type, Domain, List), X) :- !,
 4105    '$must_be'(Type, X),
 4106    (   memberchk(X, List)
 4107    ->  true
 4108    ;   '$domain_error'(Domain, X)
 4109    ).
 4110'$must_be'(boolean, X) :- !,
 4111    (   (X == true ; X == false)
 4112    ->  true
 4113    ;   '$type_error'(boolean, X)
 4114    ).
 4115'$must_be'(ground, X) :- !,
 4116    (   ground(X)
 4117    ->  true
 4118    ;   '$instantiation_error'(X)
 4119    ).
 4120'$must_be'(filespec, X) :- !,
 4121    (   (   atom(X)
 4122	;   string(X)
 4123	;   compound(X),
 4124	    compound_name_arity(X, _, 1)
 4125	)
 4126    ->  true
 4127    ;   '$type_error'(filespec, X)
 4128    ).
 4129
 4130% Use for debugging
 4131%'$must_be'(Type, _X) :- format('Unknown $must_be type: ~q~n', [Type]).
 4132
 4133
 4134		/********************************
 4135		*       LIST PROCESSING         *
 4136		*********************************/
 4137
 4138'$member'(El, [H|T]) :-
 4139    '$member_'(T, El, H).
 4140
 4141'$member_'(_, El, El).
 4142'$member_'([H|T], El, _) :-
 4143    '$member_'(T, El, H).
 4144
 4145'$append'([], L, L).
 4146'$append'([H|T], L, [H|R]) :-
 4147    '$append'(T, L, R).
 4148
 4149'$append'(ListOfLists, List) :-
 4150    '$must_be'(list, ListOfLists),
 4151    '$append_'(ListOfLists, List).
 4152
 4153'$append_'([], []).
 4154'$append_'([L|Ls], As) :-
 4155    '$append'(L, Ws, As),
 4156    '$append_'(Ls, Ws).
 4157
 4158'$select'(X, [X|Tail], Tail).
 4159'$select'(Elem, [Head|Tail], [Head|Rest]) :-
 4160    '$select'(Elem, Tail, Rest).
 4161
 4162'$reverse'(L1, L2) :-
 4163    '$reverse'(L1, [], L2).
 4164
 4165'$reverse'([], List, List).
 4166'$reverse'([Head|List1], List2, List3) :-
 4167    '$reverse'(List1, [Head|List2], List3).
 4168
 4169'$delete'([], _, []) :- !.
 4170'$delete'([Elem|Tail], Elem, Result) :-
 4171    !,
 4172    '$delete'(Tail, Elem, Result).
 4173'$delete'([Head|Tail], Elem, [Head|Rest]) :-
 4174    '$delete'(Tail, Elem, Rest).
 4175
 4176'$last'([H|T], Last) :-
 4177    '$last'(T, H, Last).
 4178
 4179'$last'([], Last, Last).
 4180'$last'([H|T], _, Last) :-
 4181    '$last'(T, H, Last).
 length(?List, ?N)
Is true when N is the length of List.
 4188:- '$iso'((length/2)). 4189
 4190length(List, Length) :-
 4191    var(Length),
 4192    !,
 4193    '$skip_list'(Length0, List, Tail),
 4194    (   Tail == []
 4195    ->  Length = Length0                    % +,-
 4196    ;   var(Tail)
 4197    ->  Tail \== Length,                    % avoid length(L,L)
 4198	'$length3'(Tail, Length, Length0)   % -,-
 4199    ;   throw(error(type_error(list, List),
 4200		    context(length/2, _)))
 4201    ).
 4202length(List, Length) :-
 4203    integer(Length),
 4204    Length >= 0,
 4205    !,
 4206    '$skip_list'(Length0, List, Tail),
 4207    (   Tail == []                          % proper list
 4208    ->  Length = Length0
 4209    ;   var(Tail)
 4210    ->  Extra is Length-Length0,
 4211	'$length'(Tail, Extra)
 4212    ;   throw(error(type_error(list, List),
 4213		    context(length/2, _)))
 4214    ).
 4215length(_, Length) :-
 4216    integer(Length),
 4217    !,
 4218    throw(error(domain_error(not_less_than_zero, Length),
 4219		context(length/2, _))).
 4220length(_, Length) :-
 4221    throw(error(type_error(integer, Length),
 4222		context(length/2, _))).
 4223
 4224'$length3'([], N, N).
 4225'$length3'([_|List], N, N0) :-
 4226    N1 is N0+1,
 4227    '$length3'(List, N, N1).
 4228
 4229
 4230		 /*******************************
 4231		 *       OPTION PROCESSING      *
 4232		 *******************************/
 $is_options(@Term) is semidet
True if Term looks like it provides options.
 4238'$is_options'(Map) :-
 4239    is_dict(Map, _),
 4240    !.
 4241'$is_options'(List) :-
 4242    is_list(List),
 4243    (   List == []
 4244    ->  true
 4245    ;   List = [H|_],
 4246	'$is_option'(H, _, _)
 4247    ).
 4248
 4249'$is_option'(Var, _, _) :-
 4250    var(Var), !, fail.
 4251'$is_option'(F, Name, Value) :-
 4252    functor(F, _, 1),
 4253    !,
 4254    F =.. [Name,Value].
 4255'$is_option'(Name=Value, Name, Value).
 $option(?Opt, +Options) is semidet
 4259'$option'(Opt, Options) :-
 4260    is_dict(Options),
 4261    !,
 4262    [Opt] :< Options.
 4263'$option'(Opt, Options) :-
 4264    memberchk(Opt, Options).
 $option(?Opt, +Options, +Default) is det
 4268'$option'(Term, Options, Default) :-
 4269    arg(1, Term, Value),
 4270    functor(Term, Name, 1),
 4271    (   is_dict(Options)
 4272    ->  (   get_dict(Name, Options, GVal)
 4273	->  Value = GVal
 4274	;   Value = Default
 4275	)
 4276    ;   functor(Gen, Name, 1),
 4277	arg(1, Gen, GVal),
 4278	(   memberchk(Gen, Options)
 4279	->  Value = GVal
 4280	;   Value = Default
 4281	)
 4282    ).
 $select_option(?Opt, +Options, -Rest) is semidet
Select an option from Options.
Arguments:
Rest- is always a map.
 4290'$select_option'(Opt, Options, Rest) :-
 4291    '$options_dict'(Options, Dict),
 4292    select_dict([Opt], Dict, Rest).
 $merge_options(+New, +Default, -Merged) is det
Add/replace options specified in New.
Arguments:
Merged- is always a map.
 4300'$merge_options'(New, Old, Merged) :-
 4301    '$options_dict'(New, NewDict),
 4302    '$options_dict'(Old, OldDict),
 4303    put_dict(NewDict, OldDict, Merged).
 $options_dict(+Options, --Dict) is det
Translate to an options dict. For possible duplicate keys we keep the first.
 4310'$options_dict'(Options, Dict) :-
 4311    is_list(Options),
 4312    !,
 4313    '$keyed_options'(Options, Keyed),
 4314    sort(1, @<, Keyed, UniqueKeyed),
 4315    '$pairs_values'(UniqueKeyed, Unique),
 4316    dict_create(Dict, _, Unique).
 4317'$options_dict'(Dict, Dict) :-
 4318    is_dict(Dict),
 4319    !.
 4320'$options_dict'(Options, _) :-
 4321    '$domain_error'(options, Options).
 4322
 4323'$keyed_options'([], []).
 4324'$keyed_options'([H0|T0], [H|T]) :-
 4325    '$keyed_option'(H0, H),
 4326    '$keyed_options'(T0, T).
 4327
 4328'$keyed_option'(Var, _) :-
 4329    var(Var),
 4330    !,
 4331    '$instantiation_error'(Var).
 4332'$keyed_option'(Name=Value, Name-(Name-Value)).
 4333'$keyed_option'(NameValue, Name-(Name-Value)) :-
 4334    compound_name_arguments(NameValue, Name, [Value]),
 4335    !.
 4336'$keyed_option'(Opt, _) :-
 4337    '$domain_error'(option, Opt).
 4338
 4339
 4340		 /*******************************
 4341		 *   HANDLE TRACER 'L'-COMMAND  *
 4342		 *******************************/
 4343
 4344:- public '$prolog_list_goal'/1. 4345
 4346:- multifile
 4347    user:prolog_list_goal/1. 4348
 4349'$prolog_list_goal'(Goal) :-
 4350    user:prolog_list_goal(Goal),
 4351    !.
 4352'$prolog_list_goal'(Goal) :-
 4353    use_module(library(listing), [listing/1]),
 4354    @(listing(Goal), user).
 4355
 4356
 4357		 /*******************************
 4358		 *             HALT             *
 4359		 *******************************/
 4360
 4361:- '$iso'((halt/0)). 4362
 4363halt :-
 4364    '$exit_code'(Code),
 4365    (   Code == 0
 4366    ->  true
 4367    ;   print_message(warning, on_error(halt(1)))
 4368    ),
 4369    halt(Code).
 $exit_code(Code)
Determine the exit code baed on the on_error and on_warning flags. Also used by qsave_toplevel/0.
 4376'$exit_code'(Code) :-
 4377    (   (   current_prolog_flag(on_error, status),
 4378	    statistics(errors, Count),
 4379	    Count > 0
 4380	;   current_prolog_flag(on_warning, status),
 4381	    statistics(warnings, Count),
 4382	    Count > 0
 4383	)
 4384    ->  Code = 1
 4385    ;   Code = 0
 4386    ).
 at_halt(:Goal)
Register Goal to be called if the system halts.
To be done
- : get location into the error message
 4395:- meta_predicate at_halt(0). 4396:- dynamic        system:term_expansion/2, '$at_halt'/2. 4397:- multifile      system:term_expansion/2, '$at_halt'/2. 4398
 4399system:term_expansion((:- at_halt(Goal)),
 4400		      system:'$at_halt'(Module:Goal, File:Line)) :-
 4401    \+ current_prolog_flag(xref, true),
 4402    source_location(File, Line),
 4403    '$current_source_module'(Module).
 4404
 4405at_halt(Goal) :-
 4406    asserta('$at_halt'(Goal, (-):0)).
 4407
 4408:- public '$run_at_halt'/0. 4409
 4410'$run_at_halt' :-
 4411    forall(clause('$at_halt'(Goal, Src), true, Ref),
 4412	   ( '$call_at_halt'(Goal, Src),
 4413	     erase(Ref)
 4414	   )).
 4415
 4416'$call_at_halt'(Goal, _Src) :-
 4417    catch(Goal, E, true),
 4418    !,
 4419    (   var(E)
 4420    ->  true
 4421    ;   subsumes_term(cancel_halt(_), E)
 4422    ->  '$print_message'(informational, E),
 4423	fail
 4424    ;   '$print_message'(error, E)
 4425    ).
 4426'$call_at_halt'(Goal, _Src) :-
 4427    '$print_message'(warning, goal_failed(at_halt, Goal)).
 cancel_halt(+Reason)
This predicate may be called from at_halt/1 handlers to cancel halting the program. If causes halt/0 to fail rather than terminating the process.
 4435cancel_halt(Reason) :-
 4436    throw(cancel_halt(Reason)).
 prolog:heartbeat
Called every N inferences of the Prolog flag heartbeat is non-zero.
 4443:- multifile prolog:heartbeat/0. 4444
 4445
 4446		/********************************
 4447		*      LOAD OTHER MODULES       *
 4448		*********************************/
 4449
 4450:- meta_predicate
 4451    '$load_wic_files'(:). 4452
 4453'$load_wic_files'(Files) :-
 4454    Files = Module:_,
 4455    '$execute_directive'('$set_source_module'(OldM, Module), [], []),
 4456    '$save_lex_state'(LexState, []),
 4457    '$style_check'(_, 0xC7),                % see style_name/2 in syspred.pl
 4458    '$compilation_mode'(OldC, wic),
 4459    consult(Files),
 4460    '$execute_directive'('$set_source_module'(OldM), [], []),
 4461    '$execute_directive'('$restore_lex_state'(LexState), [], []),
 4462    '$set_compilation_mode'(OldC).
 $load_additional_boot_files is det
Called from compileFileList() in pl-wic.c. Gets the files from "-c file ..." and loads them into the module user.
 4470:- public '$load_additional_boot_files'/0. 4471
 4472'$load_additional_boot_files' :-
 4473    current_prolog_flag(argv, Argv),
 4474    '$get_files_argv'(Argv, Files),
 4475    (   Files \== []
 4476    ->  format('Loading additional boot files~n'),
 4477	'$load_wic_files'(user:Files),
 4478	format('additional boot files loaded~n')
 4479    ;   true
 4480    ).
 4481
 4482'$get_files_argv'([], []) :- !.
 4483'$get_files_argv'(['-c'|Files], Files) :- !.
 4484'$get_files_argv'([_|Rest], Files) :-
 4485    '$get_files_argv'(Rest, Files).
 4486
 4487'$:-'(('$boot_message'('Loading Prolog startup files~n', []),
 4488       source_location(File, _Line),
 4489       file_directory_name(File, Dir),
 4490       atom_concat(Dir, '/load.pl', LoadFile),
 4491       '$load_wic_files'(system:[LoadFile]),
 4492       (   current_prolog_flag(windows, true)
 4493       ->  atom_concat(Dir, '/menu.pl', MenuFile),
 4494	   '$load_wic_files'(system:[MenuFile])
 4495       ;   true
 4496       ),
 4497       '$boot_message'('SWI-Prolog boot files loaded~n', []),
 4498       '$compilation_mode'(OldC, wic),
 4499       '$execute_directive'('$set_source_module'(user), [], []),
 4500       '$set_compilation_mode'(OldC)
 4501      ))