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)  1985-2023, 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'(:),
  102    '$notransact'(:).

 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.

  134dynamic(Spec)            :- '$set_pattr'(Spec, pred, dynamic(true)).
  135multifile(Spec)          :- '$set_pattr'(Spec, pred, multifile(true)).
  136module_transparent(Spec) :- '$set_pattr'(Spec, pred, transparent(true)).
  137discontiguous(Spec)      :- '$set_pattr'(Spec, pred, discontiguous(true)).
  138volatile(Spec)           :- '$set_pattr'(Spec, pred, volatile(true)).
  139thread_local(Spec)       :- '$set_pattr'(Spec, pred, thread_local(true)).
  140noprofile(Spec)          :- '$set_pattr'(Spec, pred, noprofile(true)).
  141public(Spec)             :- '$set_pattr'(Spec, pred, public(true)).
  142non_terminal(Spec)       :- '$set_pattr'(Spec, pred, non_terminal(true)).
  143det(Spec)                :- '$set_pattr'(Spec, pred, det(true)).
  144'$iso'(Spec)             :- '$set_pattr'(Spec, pred, iso(true)).
  145'$clausable'(Spec)       :- '$set_pattr'(Spec, pred, clausable(true)).
  146'$hide'(Spec)            :- '$set_pattr'(Spec, pred, trace(false)).
  147'$notransact'(Spec)      :- '$set_pattr'(Spec, pred, transact(false)).
  148
  149'$set_pattr'(M:Pred, How, Attr) :-
  150    '$set_pattr'(Pred, M, How, Attr).

 $set_pattr(+Spec, +Module, +From, +Attr)

Set predicate attributes. From is one of pred or directive.

  156'$set_pattr'(X, _, _, _) :-
  157    var(X),
  158    '$uninstantiation_error'(X).
  159'$set_pattr'(as(Spec,Options), M, How, Attr0) :-
  160    !,
  161    '$attr_options'(Options, Attr0, Attr),
  162    '$set_pattr'(Spec, M, How, Attr).
  163'$set_pattr'([], _, _, _) :- !.
  164'$set_pattr'([H|T], M, How, Attr) :-           % ISO
  165    !,
  166    '$set_pattr'(H, M, How, Attr),
  167    '$set_pattr'(T, M, How, Attr).
  168'$set_pattr'((A,B), M, How, Attr) :-           % ISO and traditional
  169    !,
  170    '$set_pattr'(A, M, How, Attr),
  171    '$set_pattr'(B, M, How, Attr).
  172'$set_pattr'(M:T, _, How, Attr) :-
  173    !,
  174    '$set_pattr'(T, M, How, Attr).
  175'$set_pattr'(PI, M, _, []) :-
  176    !,
  177    '$pi_head'(M:PI, Pred),
  178    '$set_table_wrappers'(Pred).
  179'$set_pattr'(A, M, How, [O|OT]) :-
  180    !,
  181    '$set_pattr'(A, M, How, O),
  182    '$set_pattr'(A, M, How, OT).
  183'$set_pattr'(A, M, pred, Attr) :-
  184    !,
  185    Attr =.. [Name,Val],
  186    '$set_pi_attr'(M:A, Name, Val).
  187'$set_pattr'(A, M, directive, Attr) :-
  188    !,
  189    Attr =.. [Name,Val],
  190    catch('$set_pi_attr'(M:A, Name, Val),
  191	  error(E, _),
  192	  print_message(error, error(E, context((Name)/1,_)))).
  193
  194'$set_pi_attr'(PI, Name, Val) :-
  195    '$pi_head'(PI, Head),
  196    '$set_predicate_attribute'(Head, Name, Val).
  197
  198'$attr_options'(Var, _, _) :-
  199    var(Var),
  200    !,
  201    '$uninstantiation_error'(Var).
  202'$attr_options'((A,B), Attr0, Attr) :-
  203    !,
  204    '$attr_options'(A, Attr0, Attr1),
  205    '$attr_options'(B, Attr1, Attr).
  206'$attr_options'(Opt, Attr0, Attrs) :-
  207    '$must_be'(ground, Opt),
  208    (   '$attr_option'(Opt, AttrX)
  209    ->  (   is_list(Attr0)
  210	->  '$join_attrs'(AttrX, Attr0, Attrs)
  211	;   '$join_attrs'(AttrX, [Attr0], Attrs)
  212	)
  213    ;   '$domain_error'(predicate_option, Opt)
  214    ).
  215
  216'$join_attrs'([], Attrs, Attrs) :-
  217    !.
  218'$join_attrs'([H|T], Attrs0, Attrs) :-
  219    !,
  220    '$join_attrs'(H, Attrs0, Attrs1),
  221    '$join_attrs'(T, Attrs1, Attrs).
  222'$join_attrs'(Attr, Attrs, Attrs) :-
  223    memberchk(Attr, Attrs),
  224    !.
  225'$join_attrs'(Attr, Attrs, Attrs) :-
  226    Attr =.. [Name,Value],
  227    Gen =.. [Name,Existing],
  228    memberchk(Gen, Attrs),
  229    !,
  230    throw(error(conflict_error(Name, Value, Existing), _)).
  231'$join_attrs'(Attr, Attrs0, Attrs) :-
  232    '$append'(Attrs0, [Attr], Attrs).
  233
  234'$attr_option'(incremental, [incremental(true),opaque(false)]).
  235'$attr_option'(monotonic, monotonic(true)).
  236'$attr_option'(lazy, lazy(true)).
  237'$attr_option'(opaque, [incremental(false),opaque(true)]).
  238'$attr_option'(abstract(Level0), abstract(Level)) :-
  239    '$table_option'(Level0, Level).
  240'$attr_option'(subgoal_abstract(Level0), subgoal_abstract(Level)) :-
  241    '$table_option'(Level0, Level).
  242'$attr_option'(answer_abstract(Level0), answer_abstract(Level)) :-
  243    '$table_option'(Level0, Level).
  244'$attr_option'(max_answers(Level0), max_answers(Level)) :-
  245    '$table_option'(Level0, Level).
  246'$attr_option'(volatile, volatile(true)).
  247'$attr_option'(multifile, multifile(true)).
  248'$attr_option'(discontiguous, discontiguous(true)).
  249'$attr_option'(shared, thread_local(false)).
  250'$attr_option'(local, thread_local(true)).
  251'$attr_option'(private, thread_local(true)).
  252
  253'$table_option'(Value0, _Value) :-
  254    var(Value0),
  255    !,
  256    '$instantiation_error'(Value0).
  257'$table_option'(Value0, Value) :-
  258    integer(Value0),
  259    Value0 >= 0,
  260    !,
  261    Value = Value0.
  262'$table_option'(off, -1) :-
  263    !.
  264'$table_option'(false, -1) :-
  265    !.
  266'$table_option'(infinite, -1) :-
  267    !.
  268'$table_option'(Value, _) :-
  269    '$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.

  279'$pattr_directive'(dynamic(Spec), M) :-
  280    '$set_pattr'(Spec, M, directive, dynamic(true)).
  281'$pattr_directive'(multifile(Spec), M) :-
  282    '$set_pattr'(Spec, M, directive, multifile(true)).
  283'$pattr_directive'(module_transparent(Spec), M) :-
  284    '$set_pattr'(Spec, M, directive, transparent(true)).
  285'$pattr_directive'(discontiguous(Spec), M) :-
  286    '$set_pattr'(Spec, M, directive, discontiguous(true)).
  287'$pattr_directive'(volatile(Spec), M) :-
  288    '$set_pattr'(Spec, M, directive, volatile(true)).
  289'$pattr_directive'(thread_local(Spec), M) :-
  290    '$set_pattr'(Spec, M, directive, thread_local(true)).
  291'$pattr_directive'(noprofile(Spec), M) :-
  292    '$set_pattr'(Spec, M, directive, noprofile(true)).
  293'$pattr_directive'(public(Spec), M) :-
  294    '$set_pattr'(Spec, M, directive, public(true)).
  295'$pattr_directive'(det(Spec), M) :-
  296    '$set_pattr'(Spec, M, directive, det(true)).

 $pi_head(?PI, ?Head)

  300'$pi_head'(PI, Head) :-
  301    var(PI),
  302    var(Head),
  303    '$instantiation_error'([PI,Head]).
  304'$pi_head'(M:PI, M:Head) :-
  305    !,
  306    '$pi_head'(PI, Head).
  307'$pi_head'(Name/Arity, Head) :-
  308    !,
  309    '$head_name_arity'(Head, Name, Arity).
  310'$pi_head'(Name//DCGArity, Head) :-
  311    !,
  312    (   nonvar(DCGArity)
  313    ->  Arity is DCGArity+2,
  314	'$head_name_arity'(Head, Name, Arity)
  315    ;   '$head_name_arity'(Head, Name, Arity),
  316	DCGArity is Arity - 2
  317    ).
  318'$pi_head'(PI, _) :-
  319    '$type_error'(predicate_indicator, PI).

 $head_name_arity(+Goal, -Name, -Arity)

$head_name_arity(-Goal, +Name, +Arity)

  324'$head_name_arity'(Goal, Name, Arity) :-
  325    (   atom(Goal)
  326    ->  Name = Goal, Arity = 0
  327    ;   compound(Goal)
  328    ->  compound_name_arity(Goal, Name, Arity)
  329    ;   var(Goal)
  330    ->  (   Arity == 0
  331	->  (   atom(Name)
  332	    ->  Goal = Name
  333	    ;   Name == []
  334	    ->  Goal = Name
  335	    ;   blob(Name, closure)
  336	    ->  Goal = Name
  337	    ;   '$type_error'(atom, Name)
  338	    )
  339	;   compound_name_arity(Goal, Name, Arity)
  340	)
  341    ;   '$type_error'(callable, Goal)
  342    ).
  343
  344:- '$iso'(((dynamic)/1, (multifile)/1, (discontiguous)/1)).  345
  346
  347		/********************************
  348		*       CALLING, CONTROL        *
  349		*********************************/
  350
  351:- noprofile((call/1,
  352	      catch/3,
  353	      once/1,
  354	      ignore/1,
  355	      call_cleanup/2,
  356	      setup_call_cleanup/3,
  357	      setup_call_catcher_cleanup/4,
  358	      notrace/1)).  359
  360:- meta_predicate
  361    ';'(0,0),
  362    ','(0,0),
  363    @(0,+),
  364    call(0),
  365    call(1,?),
  366    call(2,?,?),
  367    call(3,?,?,?),
  368    call(4,?,?,?,?),
  369    call(5,?,?,?,?,?),
  370    call(6,?,?,?,?,?,?),
  371    call(7,?,?,?,?,?,?,?),
  372    not(0),
  373    \+(0),
  374    $(0),
  375    '->'(0,0),
  376    '*->'(0,0),
  377    once(0),
  378    ignore(0),
  379    catch(0,?,0),
  380    reset(0,?,-),
  381    setup_call_cleanup(0,0,0),
  382    setup_call_catcher_cleanup(0,0,?,0),
  383    call_cleanup(0,0),
  384    catch_with_backtrace(0,?,0),
  385    notrace(0),
  386    '$meta_call'(0).  387
  388:- '$iso'((call/1, (\+)/1, once/1, (;)/2, (',')/2, (->)/2, catch/3)).  389
  390% The control structures are always compiled, both   if they appear in a
  391% clause body and if they are handed  to   call/1.  The only way to call
  392% these predicates is by means of  call/2..   In  that case, we call the
  393% hole control structure again to get it compiled by call/1 and properly
  394% deal  with  !,  etc.  Another  reason  for  having  these  things   as
  395% predicates is to be able to define   properties for them, helping code
  396% analyzers.
  397
  398(M0:If ; M0:Then) :- !, call(M0:(If ; Then)).
  399(M1:If ; M2:Then) :-    call(M1:(If ; M2:Then)).
  400(G1   , G2)       :-    call((G1   , G2)).
  401(If  -> Then)     :-    call((If  -> Then)).
  402(If *-> Then)     :-    call((If *-> Then)).
  403@(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.

  417'$meta_call'(M:G) :-
  418    prolog_current_choice(Ch),
  419    '$meta_call'(G, M, Ch).
  420
  421'$meta_call'(Var, _, _) :-
  422    var(Var),
  423    !,
  424    '$instantiation_error'(Var).
  425'$meta_call'((A,B), M, Ch) :-
  426    !,
  427    '$meta_call'(A, M, Ch),
  428    '$meta_call'(B, M, Ch).
  429'$meta_call'((I->T;E), M, Ch) :-
  430    !,
  431    (   prolog_current_choice(Ch2),
  432	'$meta_call'(I, M, Ch2)
  433    ->  '$meta_call'(T, M, Ch)
  434    ;   '$meta_call'(E, M, Ch)
  435    ).
  436'$meta_call'((I*->T;E), M, Ch) :-
  437    !,
  438    (   prolog_current_choice(Ch2),
  439	'$meta_call'(I, M, Ch2)
  440    *-> '$meta_call'(T, M, Ch)
  441    ;   '$meta_call'(E, M, Ch)
  442    ).
  443'$meta_call'((I->T), M, Ch) :-
  444    !,
  445    (   prolog_current_choice(Ch2),
  446	'$meta_call'(I, M, Ch2)
  447    ->  '$meta_call'(T, M, Ch)
  448    ).
  449'$meta_call'((I*->T), M, Ch) :-
  450    !,
  451    prolog_current_choice(Ch2),
  452    '$meta_call'(I, M, Ch2),
  453    '$meta_call'(T, M, Ch).
  454'$meta_call'((A;B), M, Ch) :-
  455    !,
  456    (   '$meta_call'(A, M, Ch)
  457    ;   '$meta_call'(B, M, Ch)
  458    ).
  459'$meta_call'(\+(G), M, _) :-
  460    !,
  461    prolog_current_choice(Ch),
  462    \+ '$meta_call'(G, M, Ch).
  463'$meta_call'($(G), M, _) :-
  464    !,
  465    prolog_current_choice(Ch),
  466    $('$meta_call'(G, M, Ch)).
  467'$meta_call'(call(G), M, _) :-
  468    !,
  469    prolog_current_choice(Ch),
  470    '$meta_call'(G, M, Ch).
  471'$meta_call'(M:G, _, Ch) :-
  472    !,
  473    '$meta_call'(G, M, Ch).
  474'$meta_call'(!, _, Ch) :-
  475    prolog_cut_to(Ch).
  476'$meta_call'(G, M, _Ch) :-
  477    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..

  493:- '$iso'((call/2,
  494	   call/3,
  495	   call/4,
  496	   call/5,
  497	   call/6,
  498	   call/7,
  499	   call/8)).  500
  501call(Goal) :-                           % make these available as predicates
  502    Goal.
  503call(Goal, A) :-
  504    call(Goal, A).
  505call(Goal, A, B) :-
  506    call(Goal, A, B).
  507call(Goal, A, B, C) :-
  508    call(Goal, A, B, C).
  509call(Goal, A, B, C, D) :-
  510    call(Goal, A, B, C, D).
  511call(Goal, A, B, C, D, E) :-
  512    call(Goal, A, B, C, D, E).
  513call(Goal, A, B, C, D, E, F) :-
  514    call(Goal, A, B, C, D, E, F).
  515call(Goal, A, B, C, D, E, F, G) :-
  516    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.

  523not(Goal) :-
  524    \+ Goal.

 \+ :Goal is semidet

Predicate version that allows for meta-calling.

  530\+ Goal :-
  531    \+ Goal.

 once(:Goal) is semidet

ISO predicate, acting as call((Goal, !)).

  537once(Goal) :-
  538    Goal,
  539    !.

 ignore(:Goal) is det

Call Goal, cut choice-points on success and succeed on failure. intended for calling side-effects and proceed on failure.

  546ignore(Goal) :-
  547    Goal,
  548    !.
  549ignore(_Goal).
  550
  551:- '$iso'((false/0)).

 false

Synonym for fail/0, providing a declarative reading.

  557false :-
  558    fail.

 catch(:Goal, +Catcher, :Recover)

ISO compliant exception handling.

  564catch(_Goal, _Catcher, _Recover) :-
  565    '$catch'.                       % Maps to I_CATCH, I_EXITCATCH

 prolog_cut_to(+Choice)

Cut all choice points after Choice

  571prolog_cut_to(_Choice) :-
  572    '$cut'.                         % Maps to I_CUTCHP

 $ is det

Declare that from now on this predicate succeeds deterministically.

  578'$' :- '$'.

 $ :Goal is det

Declare that Goal must succeed deterministically.

  584$(Goal) :- $(Goal).

 notrace(:Goal) is semidet

Suspend the tracer while running Goal.

  590:- '$hide'(notrace/1).  591
  592notrace(Goal) :-
  593    setup_call_cleanup(
  594	'$notrace'(Flags, SkipLevel),
  595	once(Goal),
  596	'$restore_trace'(Flags, SkipLevel)).

 reset(:Goal, ?Ball, -Continue)

Delimited continuation support.

  603reset(_Goal, _Ball, _Cont) :-
  604    '$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.

  613shift(Ball) :-
  614    '$shift'(Ball).
  615
  616shift_for_copy(Ball) :-
  617    '$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.

  631call_continuation([]).
  632call_continuation([TB|Rest]) :-
  633    (   Rest == []
  634    ->  '$call_continuation'(TB)
  635    ;   '$call_continuation'(TB),
  636	call_continuation(Rest)
  637    ).

 catch_with_backtrace(:Goal, ?Ball, :Recover)

As catch/3, but tell library(prolog_stack) to record a backtrace in case of an exception.

  644catch_with_backtrace(Goal, Ball, Recover) :-
  645    catch(Goal, Ball, Recover),
  646    '$no_lco'.
  647
  648'$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.

  658:- public '$recover_and_rethrow'/2.  659
  660'$recover_and_rethrow'(Goal, Exception) :-
  661    call_cleanup(Goal, throw(Exception)),
  662    !.

 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.

  676setup_call_catcher_cleanup(Setup, _Goal, _Catcher, _Cleanup) :-
  677    sig_atomic(Setup),
  678    '$call_cleanup'.
  679
  680setup_call_cleanup(Setup, _Goal, _Cleanup) :-
  681    sig_atomic(Setup),
  682    '$call_cleanup'.
  683
  684call_cleanup(_Goal, _Cleanup) :-
  685    '$call_cleanup'.
  686
  687
  688		 /*******************************
  689		 *       INITIALIZATION         *
  690		 *******************************/
  691
  692:- meta_predicate
  693    initialization(0, +).  694
  695:- multifile '$init_goal'/3.  696:- dynamic   '$init_goal'/3.  697:- '$notransact'('$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.

  723initialization(Goal, When) :-
  724    '$must_be'(oneof(atom, initialization_type,
  725		     [ now,
  726		       after_load,
  727		       restore,
  728		       restore_state,
  729		       prepare_state,
  730		       program,
  731		       main
  732		     ]), When),
  733    '$initialization_context'(Source, Ctx),
  734    '$initialization'(When, Goal, Source, Ctx).
  735
  736'$initialization'(now, Goal, _Source, Ctx) :-
  737    '$run_init_goal'(Goal, Ctx),
  738    '$compile_init_goal'(-, Goal, Ctx).
  739'$initialization'(after_load, Goal, Source, Ctx) :-
  740    (   Source \== (-)
  741    ->  '$compile_init_goal'(Source, Goal, Ctx)
  742    ;   throw(error(context_error(nodirective,
  743				  initialization(Goal, after_load)),
  744		    _))
  745    ).
  746'$initialization'(restore, Goal, Source, Ctx) :- % deprecated
  747    '$initialization'(restore_state, Goal, Source, Ctx).
  748'$initialization'(restore_state, Goal, _Source, Ctx) :-
  749    (   \+ current_prolog_flag(sandboxed_load, true)
  750    ->  '$compile_init_goal'(-, Goal, Ctx)
  751    ;   '$permission_error'(register, initialization(restore), Goal)
  752    ).
  753'$initialization'(prepare_state, Goal, _Source, Ctx) :-
  754    (   \+ current_prolog_flag(sandboxed_load, true)
  755    ->  '$compile_init_goal'(when(prepare_state), Goal, Ctx)
  756    ;   '$permission_error'(register, initialization(restore), Goal)
  757    ).
  758'$initialization'(program, Goal, _Source, Ctx) :-
  759    (   \+ current_prolog_flag(sandboxed_load, true)
  760    ->  '$compile_init_goal'(when(program), Goal, Ctx)
  761    ;   '$permission_error'(register, initialization(restore), Goal)
  762    ).
  763'$initialization'(main, Goal, _Source, Ctx) :-
  764    (   \+ current_prolog_flag(sandboxed_load, true)
  765    ->  '$compile_init_goal'(when(main), Goal, Ctx)
  766    ;   '$permission_error'(register, initialization(restore), Goal)
  767    ).
  768
  769
  770'$compile_init_goal'(Source, Goal, Ctx) :-
  771    atom(Source),
  772    Source \== (-),
  773    !,
  774    '$store_admin_clause'(system:'$init_goal'(Source, Goal, Ctx),
  775			  _Layout, Source, Ctx).
  776'$compile_init_goal'(Source, Goal, Ctx) :-
  777    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.

  789'$run_initialization'(_, loaded, _) :- !.
  790'$run_initialization'(File, _Action, Options) :-
  791    '$run_initialization'(File, Options).
  792
  793'$run_initialization'(File, Options) :-
  794    setup_call_cleanup(
  795	'$start_run_initialization'(Options, Restore),
  796	'$run_initialization_2'(File),
  797	'$end_run_initialization'(Restore)).
  798
  799'$start_run_initialization'(Options, OldSandBoxed) :-
  800    '$push_input_context'(initialization),
  801    '$set_sandboxed_load'(Options, OldSandBoxed).
  802'$end_run_initialization'(OldSandBoxed) :-
  803    set_prolog_flag(sandboxed_load, OldSandBoxed),
  804    '$pop_input_context'.
  805
  806'$run_initialization_2'(File) :-
  807    (   '$init_goal'(File, Goal, Ctx),
  808	File \= when(_),
  809	'$run_init_goal'(Goal, Ctx),
  810	fail
  811    ;   true
  812    ).
  813
  814'$run_init_goal'(Goal, Ctx) :-
  815    (   catch_with_backtrace('$run_init_goal'(Goal), E,
  816			     '$initialization_error'(E, Goal, Ctx))
  817    ->  true
  818    ;   '$initialization_failure'(Goal, Ctx)
  819    ).
  820
  821:- multifile prolog:sandbox_allowed_goal/1.  822
  823'$run_init_goal'(Goal) :-
  824    current_prolog_flag(sandboxed_load, false),
  825    !,
  826    call(Goal).
  827'$run_init_goal'(Goal) :-
  828    prolog:sandbox_allowed_goal(Goal),
  829    call(Goal).
  830
  831'$initialization_context'(Source, Ctx) :-
  832    (   source_location(File, Line)
  833    ->  Ctx = File:Line,
  834	'$input_context'(Context),
  835	'$top_file'(Context, File, Source)
  836    ;   Ctx = (-),
  837	File = (-)
  838    ).
  839
  840'$top_file'([input(include, F1, _, _)|T], _, F) :-
  841    !,
  842    '$top_file'(T, F1, F).
  843'$top_file'(_, F, F).
  844
  845
  846'$initialization_error'(E, Goal, Ctx) :-
  847    print_message(error, initialization_error(Goal, E, Ctx)).
  848
  849'$initialization_failure'(Goal, Ctx) :-
  850    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

  858:- public '$clear_source_admin'/1.  859
  860'$clear_source_admin'(File) :-
  861    retractall('$init_goal'(_, _, File:_)),
  862    retractall('$load_context_module'(File, _, _)),
  863    retractall('$resolved_source_path_db'(_, _, File)).
  864
  865
  866		 /*******************************
  867		 *            STREAM            *
  868		 *******************************/
  869
  870:- '$iso'(stream_property/2).  871stream_property(Stream, Property) :-
  872    nonvar(Stream),
  873    nonvar(Property),
  874    !,
  875    '$stream_property'(Stream, Property).
  876stream_property(Stream, Property) :-
  877    nonvar(Stream),
  878    !,
  879    '$stream_properties'(Stream, Properties),
  880    '$member'(Property, Properties).
  881stream_property(Stream, Property) :-
  882    nonvar(Property),
  883    !,
  884    (   Property = alias(Alias),
  885	atom(Alias)
  886    ->  '$alias_stream'(Alias, Stream)
  887    ;   '$streams_properties'(Property, Pairs),
  888	'$member'(Stream-Property, Pairs)
  889    ).
  890stream_property(Stream, Property) :-
  891    '$streams_properties'(Property, Pairs),
  892    '$member'(Stream-Properties, Pairs),
  893    '$member'(Property, Properties).
  894
  895
  896		/********************************
  897		*            MODULES            *
  898		*********************************/
  899
  900%       '$prefix_module'(+Module, +Context, +Term, -Prefixed)
  901%       Tags `Term' with `Module:' if `Module' is not the context module.
  902
  903'$prefix_module'(Module, Module, Head, Head) :- !.
  904'$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'.

  910default_module(Me, Super) :-
  911    (   atom(Me)
  912    ->  (   var(Super)
  913	->  '$default_module'(Me, Super)
  914	;   '$default_module'(Me, Super), !
  915	)
  916    ;   '$type_error'(module, Me)
  917    ).
  918
  919'$default_module'(Me, Me).
  920'$default_module'(Me, Super) :-
  921    import_module(Me, S),
  922    '$default_module'(S, Super).
  923
  924
  925		/********************************
  926		*      TRACE AND EXCEPTIONS     *
  927		*********************************/
  928
  929:- dynamic   user:exception/3.  930:- multifile user:exception/3.  931:- '$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.

  940:- public
  941    '$undefined_procedure'/4.  942
  943'$undefined_procedure'(Module, Name, Arity, Action) :-
  944    '$prefix_module'(Module, user, Name/Arity, Pred),
  945    user:exception(undefined_predicate, Pred, Action0),
  946    !,
  947    Action = Action0.
  948'$undefined_procedure'(Module, Name, Arity, Action) :-
  949    \+ current_prolog_flag(autoload, false),
  950    '$autoload'(Module:Name/Arity),
  951    !,
  952    Action = retry.
  953'$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.

  965'$loading'(Library) :-
  966    current_prolog_flag(threads, true),
  967    (   '$loading_file'(Library, _Queue, _LoadThread)
  968    ->  true
  969    ;   '$loading_file'(FullFile, _Queue, _LoadThread),
  970	file_name_extension(Library, _, FullFile)
  971    ->  true
  972    ).
  973
  974%        handle debugger 'w', 'p' and <N> depth options.
  975
  976'$set_debugger_write_options'(write) :-
  977    !,
  978    create_prolog_flag(debugger_write_options,
  979		       [ quoted(true),
  980			 attributes(dots),
  981			 spacing(next_argument)
  982		       ], []).
  983'$set_debugger_write_options'(print) :-
  984    !,
  985    create_prolog_flag(debugger_write_options,
  986		       [ quoted(true),
  987			 portray(true),
  988			 max_depth(10),
  989			 attributes(portray),
  990			 spacing(next_argument)
  991		       ], []).
  992'$set_debugger_write_options'(Depth) :-
  993    current_prolog_flag(debugger_write_options, Options0),
  994    (   '$select'(max_depth(_), Options0, Options)
  995    ->  true
  996    ;   Options = Options0
  997    ),
  998    create_prolog_flag(debugger_write_options,
  999		       [max_depth(Depth)|Options], []).
 1000
 1001
 1002		/********************************
 1003		*        SYSTEM MESSAGES        *
 1004		*********************************/

 $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.

 1013:- multifile
 1014    prolog:confirm/2. 1015
 1016'$confirm'(Spec) :-
 1017    prolog:confirm(Spec, Result),
 1018    !,
 1019    Result == true.
 1020'$confirm'(Spec) :-
 1021    print_message(query, Spec),
 1022    between(0, 5, _),
 1023	get_single_char(Answer),
 1024	(   '$in_reply'(Answer, 'yYjJ \n')
 1025	->  !,
 1026	    print_message(query, if_tty([yes-[]]))
 1027	;   '$in_reply'(Answer, 'nN')
 1028	->  !,
 1029	    print_message(query, if_tty([no-[]])),
 1030	    fail
 1031	;   print_message(help, query(confirm)),
 1032	    fail
 1033	).
 1034
 1035'$in_reply'(Code, Atom) :-
 1036    char_code(Char, Code),
 1037    sub_atom(Atom, _, _, _, Char),
 1038    !.
 1039
 1040:- dynamic
 1041    user:portray/1. 1042:- multifile
 1043    user:portray/1. 1044:- '$notransact'(user:portray/1). 1045
 1046
 1047		 /*******************************
 1048		 *       FILE_SEARCH_PATH       *
 1049		 *******************************/
 1050
 1051:- dynamic
 1052    user:file_search_path/2,
 1053    user:library_directory/1. 1054:- multifile
 1055    user:file_search_path/2,
 1056    user:library_directory/1. 1057:- '$notransact'((user:file_search_path/2,
 1058                  user:library_directory/1)). 1059
 1060user:(file_search_path(library, Dir) :-
 1061	library_directory(Dir)).
 1062user:file_search_path(swi, Home) :-
 1063    current_prolog_flag(home, Home).
 1064user:file_search_path(swi, Home) :-
 1065    current_prolog_flag(shared_home, Home).
 1066user:file_search_path(library, app_config(lib)).
 1067user:file_search_path(library, swi(library)).
 1068user:file_search_path(library, swi(library/clp)).
 1069user:file_search_path(library, Dir) :-
 1070    '$ext_library_directory'(Dir).
 1071user:file_search_path(foreign, swi(ArchLib)) :-
 1072    current_prolog_flag(apple_universal_binary, true),
 1073    ArchLib = 'lib/fat-darwin'.
 1074user:file_search_path(path, Dir) :-
 1075    getenv('PATH', Path),
 1076    (   current_prolog_flag(windows, true)
 1077    ->  atomic_list_concat(Dirs, (;), Path)
 1078    ;   atomic_list_concat(Dirs, :, Path)
 1079    ),
 1080    '$member'(Dir, Dirs).
 1081user:file_search_path(user_app_data, Dir) :-
 1082    '$xdg_prolog_directory'(data, Dir).
 1083user:file_search_path(common_app_data, Dir) :-
 1084    '$xdg_prolog_directory'(common_data, Dir).
 1085user:file_search_path(user_app_config, Dir) :-
 1086    '$xdg_prolog_directory'(config, Dir).
 1087user:file_search_path(common_app_config, Dir) :-
 1088    '$xdg_prolog_directory'(common_config, Dir).
 1089user:file_search_path(app_data, user_app_data('.')).
 1090user:file_search_path(app_data, common_app_data('.')).
 1091user:file_search_path(app_config, user_app_config('.')).
 1092user:file_search_path(app_config, common_app_config('.')).
 1093% backward compatibility
 1094user:file_search_path(app_preferences, user_app_config('.')).
 1095user:file_search_path(user_profile, app_preferences('.')).
 1096user:file_search_path(app, swi(app)).
 1097user:file_search_path(app, app_data(app)).
 1098
 1099'$xdg_prolog_directory'(Which, Dir) :-
 1100    '$xdg_directory'(Which, XDGDir),
 1101    '$make_config_dir'(XDGDir),
 1102    '$ensure_slash'(XDGDir, XDGDirS),
 1103    atom_concat(XDGDirS, 'swi-prolog', Dir),
 1104    '$make_config_dir'(Dir).
 1105
 1106% config
 1107'$xdg_directory'(config, Home) :-
 1108    current_prolog_flag(windows, true),
 1109    catch(win_folder(appdata, Home), _, fail),
 1110    !.
 1111'$xdg_directory'(config, Home) :-
 1112    getenv('XDG_CONFIG_HOME', Home).
 1113'$xdg_directory'(config, Home) :-
 1114    expand_file_name('~/.config', [Home]).
 1115% data
 1116'$xdg_directory'(data, Home) :-
 1117    current_prolog_flag(windows, true),
 1118    catch(win_folder(local_appdata, Home), _, fail),
 1119    !.
 1120'$xdg_directory'(data, Home) :-
 1121    getenv('XDG_DATA_HOME', Home).
 1122'$xdg_directory'(data, Home) :-
 1123    expand_file_name('~/.local', [Local]),
 1124    '$make_config_dir'(Local),
 1125    atom_concat(Local, '/share', Home),
 1126    '$make_config_dir'(Home).
 1127% common data
 1128'$xdg_directory'(common_data, Dir) :-
 1129    current_prolog_flag(windows, true),
 1130    catch(win_folder(common_appdata, Dir), _, fail),
 1131    !.
 1132'$xdg_directory'(common_data, Dir) :-
 1133    '$existing_dir_from_env_path'('XDG_DATA_DIRS',
 1134				  [ '/usr/local/share',
 1135				    '/usr/share'
 1136				  ],
 1137				  Dir).
 1138% common config
 1139'$xdg_directory'(common_config, Dir) :-
 1140    current_prolog_flag(windows, true),
 1141    catch(win_folder(common_appdata, Dir), _, fail),
 1142    !.
 1143'$xdg_directory'(common_config, Dir) :-
 1144    '$existing_dir_from_env_path'('XDG_CONFIG_DIRS', ['/etc/xdg'], Dir).
 1145
 1146'$existing_dir_from_env_path'(Env, Defaults, Dir) :-
 1147    (   getenv(Env, Path)
 1148    ->  current_prolog_flag(path_sep, Sep),
 1149	atomic_list_concat(Dirs, Sep, Path)
 1150    ;   Dirs = Defaults
 1151    ),
 1152    '$member'(Dir, Dirs),
 1153    Dir \== '',
 1154    exists_directory(Dir).
 1155
 1156'$make_config_dir'(Dir) :-
 1157    exists_directory(Dir),
 1158    !.
 1159'$make_config_dir'(Dir) :-
 1160    nb_current('$create_search_directories', true),
 1161    file_directory_name(Dir, Parent),
 1162    '$my_file'(Parent),
 1163    catch(make_directory(Dir), _, fail).
 1164
 1165'$ensure_slash'(Dir, DirS) :-
 1166    (   sub_atom(Dir, _, _, 0, /)
 1167    ->  DirS = Dir
 1168    ;   atom_concat(Dir, /, DirS)
 1169    ).
 1170
 1171:- dynamic '$ext_lib_dirs'/1. 1172:- volatile '$ext_lib_dirs'/1. 1173
 1174'$ext_library_directory'(Dir) :-
 1175    '$ext_lib_dirs'(Dirs),
 1176    !,
 1177    '$member'(Dir, Dirs).
 1178'$ext_library_directory'(Dir) :-
 1179    current_prolog_flag(home, Home),
 1180    atom_concat(Home, '/library/ext/*', Pattern),
 1181    expand_file_name(Pattern, Dirs0),
 1182    '$include'(exists_directory, Dirs0, Dirs),
 1183    asserta('$ext_lib_dirs'(Dirs)),
 1184    '$member'(Dir, Dirs).

 $expand_file_search_path(+Spec, -Expanded, +Cond) is nondet

 1189'$expand_file_search_path'(Spec, Expanded, Cond) :-
 1190    '$option'(access(Access), Cond),
 1191    memberchk(Access, [write,append]),
 1192    !,
 1193    setup_call_cleanup(
 1194	nb_setval('$create_search_directories', true),
 1195	expand_file_search_path(Spec, Expanded),
 1196	nb_delete('$create_search_directories')).
 1197'$expand_file_search_path'(Spec, Expanded, _Cond) :-
 1198    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?

 1206expand_file_search_path(Spec, Expanded) :-
 1207    catch('$expand_file_search_path'(Spec, Expanded, 0, []),
 1208	  loop(Used),
 1209	  throw(error(loop_error(Spec), file_search(Used)))).
 1210
 1211'$expand_file_search_path'(Spec, Expanded, N, Used) :-
 1212    functor(Spec, Alias, 1),
 1213    !,
 1214    user:file_search_path(Alias, Exp0),
 1215    NN is N + 1,
 1216    (   NN > 16
 1217    ->  throw(loop(Used))
 1218    ;   true
 1219    ),
 1220    '$expand_file_search_path'(Exp0, Exp1, NN, [Alias=Exp0|Used]),
 1221    arg(1, Spec, Segments),
 1222    '$segments_to_atom'(Segments, File),
 1223    '$make_path'(Exp1, File, Expanded).
 1224'$expand_file_search_path'(Spec, Path, _, _) :-
 1225    '$segments_to_atom'(Spec, Path).
 1226
 1227'$make_path'(Dir, '.', Path) :-
 1228    !,
 1229    Path = Dir.
 1230'$make_path'(Dir, File, Path) :-
 1231    sub_atom(Dir, _, _, 0, /),
 1232    !,
 1233    atom_concat(Dir, File, Path).
 1234'$make_path'(Dir, File, Path) :-
 1235    atomic_list_concat([Dir, /, File], Path).
 1236
 1237
 1238		/********************************
 1239		*         FILE CHECKING         *
 1240		*********************************/

 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.

 1251absolute_file_name(Spec, Options, Path) :-
 1252    '$is_options'(Options),
 1253    \+ '$is_options'(Path),
 1254    !,
 1255    '$absolute_file_name'(Spec, Path, Options).
 1256absolute_file_name(Spec, Path, Options) :-
 1257    '$absolute_file_name'(Spec, Path, Options).
 1258
 1259'$absolute_file_name'(Spec, Path, Options0) :-
 1260    '$options_dict'(Options0, Options),
 1261		    % get the valid extensions
 1262    (   '$select_option'(extensions(Exts), Options, Options1)
 1263    ->  '$must_be'(list, Exts)
 1264    ;   '$option'(file_type(Type), Options)
 1265    ->  '$must_be'(atom, Type),
 1266	'$file_type_extensions'(Type, Exts),
 1267	Options1 = Options
 1268    ;   Options1 = Options,
 1269	Exts = ['']
 1270    ),
 1271    '$canonicalise_extensions'(Exts, Extensions),
 1272		    % unless specified otherwise, ask regular file
 1273    (   (   nonvar(Type)
 1274	;   '$option'(access(none), Options, none)
 1275	)
 1276    ->  Options2 = Options1
 1277    ;   '$merge_options'(_{file_type:regular}, Options1, Options2)
 1278    ),
 1279		    % Det or nondet?
 1280    (   '$select_option'(solutions(Sols), Options2, Options3)
 1281    ->  '$must_be'(oneof(atom, solutions, [first,all]), Sols)
 1282    ;   Sols = first,
 1283	Options3 = Options2
 1284    ),
 1285		    % Errors or not?
 1286    (   '$select_option'(file_errors(FileErrors), Options3, Options4)
 1287    ->  '$must_be'(oneof(atom, file_errors, [error,fail]), FileErrors)
 1288    ;   FileErrors = error,
 1289	Options4 = Options3
 1290    ),
 1291		    % Expand shell patterns?
 1292    (   atomic(Spec),
 1293	'$select_option'(expand(Expand), Options4, Options5),
 1294	'$must_be'(boolean, Expand)
 1295    ->  expand_file_name(Spec, List),
 1296	'$member'(Spec1, List)
 1297    ;   Spec1 = Spec,
 1298	Options5 = Options4
 1299    ),
 1300		    % Search for files
 1301    (   Sols == first
 1302    ->  (   '$chk_file'(Spec1, Extensions, Options5, true, Path)
 1303	->  !       % also kill choice point of expand_file_name/2
 1304	;   (   FileErrors == fail
 1305	    ->  fail
 1306	    ;   '$current_module'('$bags', _File),
 1307		findall(P,
 1308			'$chk_file'(Spec1, Extensions, [access(exist)],
 1309				    false, P),
 1310			Candidates),
 1311		'$abs_file_error'(Spec, Candidates, Options5)
 1312	    )
 1313	)
 1314    ;   '$chk_file'(Spec1, Extensions, Options5, false, Path)
 1315    ).
 1316
 1317'$abs_file_error'(Spec, Candidates, Conditions) :-
 1318    '$member'(F, Candidates),
 1319    '$member'(C, Conditions),
 1320    '$file_condition'(C),
 1321    '$file_error'(C, Spec, F, E, Comment),
 1322    !,
 1323    throw(error(E, context(_, Comment))).
 1324'$abs_file_error'(Spec, _, _) :-
 1325    '$existence_error'(source_sink, Spec).
 1326
 1327'$file_error'(file_type(directory), Spec, File, Error, Comment) :-
 1328    \+ exists_directory(File),
 1329    !,
 1330    Error = existence_error(directory, Spec),
 1331    Comment = not_a_directory(File).
 1332'$file_error'(file_type(_), Spec, File, Error, Comment) :-
 1333    exists_directory(File),
 1334    !,
 1335    Error = existence_error(file, Spec),
 1336    Comment = directory(File).
 1337'$file_error'(access(OneOrList), Spec, File, Error, _) :-
 1338    '$one_or_member'(Access, OneOrList),
 1339    \+ access_file(File, Access),
 1340    Error = permission_error(Access, source_sink, Spec).
 1341
 1342'$one_or_member'(Elem, List) :-
 1343    is_list(List),
 1344    !,
 1345    '$member'(Elem, List).
 1346'$one_or_member'(Elem, Elem).
 1347
 1348
 1349'$file_type_extensions'(source, Exts) :-       % SICStus 3.9 compatibility
 1350    !,
 1351    '$file_type_extensions'(prolog, Exts).
 1352'$file_type_extensions'(Type, Exts) :-
 1353    '$current_module'('$bags', _File),
 1354    !,
 1355    findall(Ext, user:prolog_file_type(Ext, Type), Exts0),
 1356    (   Exts0 == [],
 1357	\+ '$ft_no_ext'(Type)
 1358    ->  '$domain_error'(file_type, Type)
 1359    ;   true
 1360    ),
 1361    '$append'(Exts0, [''], Exts).
 1362'$file_type_extensions'(prolog, [pl, '']). % findall is not yet defined ...
 1363
 1364'$ft_no_ext'(txt).
 1365'$ft_no_ext'(executable).
 1366'$ft_no_ext'(directory).
 1367'$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.

 1380:- multifile(user:prolog_file_type/2). 1381:- dynamic(user:prolog_file_type/2). 1382
 1383user:prolog_file_type(pl,       prolog).
 1384user:prolog_file_type(prolog,   prolog).
 1385user:prolog_file_type(qlf,      prolog).
 1386user:prolog_file_type(qlf,      qlf).
 1387user:prolog_file_type(Ext,      executable) :-
 1388    current_prolog_flag(shared_object_extension, Ext).
 1389user:prolog_file_type(dylib,    executable) :-
 1390    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.

 1397'$chk_file'(Spec, _Extensions, _Cond, _Cache, _FullName) :-
 1398    \+ ground(Spec),
 1399    !,
 1400    '$instantiation_error'(Spec).
 1401'$chk_file'(Spec, Extensions, Cond, Cache, FullName) :-
 1402    compound(Spec),
 1403    functor(Spec, _, 1),
 1404    !,
 1405    '$relative_to'(Cond, cwd, CWD),
 1406    '$chk_alias_file'(Spec, Extensions, Cond, Cache, CWD, FullName).
 1407'$chk_file'(Segments, Ext, Cond, Cache, FullName) :-    % allow a/b/...
 1408    \+ atomic(Segments),
 1409    !,
 1410    '$segments_to_atom'(Segments, Atom),
 1411    '$chk_file'(Atom, Ext, Cond, Cache, FullName).
 1412'$chk_file'(File, Exts, Cond, _, FullName) :-
 1413    is_absolute_file_name(File),
 1414    !,
 1415    '$extend_file'(File, Exts, Extended),
 1416    '$file_conditions'(Cond, Extended),
 1417    '$absolute_file_name'(Extended, FullName).
 1418'$chk_file'(File, Exts, Cond, _, FullName) :-
 1419    '$relative_to'(Cond, source, Dir),
 1420    atomic_list_concat([Dir, /, File], AbsFile),
 1421    '$extend_file'(AbsFile, Exts, Extended),
 1422    '$file_conditions'(Cond, Extended),
 1423    !,
 1424    '$absolute_file_name'(Extended, FullName).
 1425'$chk_file'(File, Exts, Cond, _, FullName) :-
 1426    '$extend_file'(File, Exts, Extended),
 1427    '$file_conditions'(Cond, Extended),
 1428    '$absolute_file_name'(Extended, FullName).
 1429
 1430'$segments_to_atom'(Atom, Atom) :-
 1431    atomic(Atom),
 1432    !.
 1433'$segments_to_atom'(Segments, Atom) :-
 1434    '$segments_to_list'(Segments, List, []),
 1435    !,
 1436    atomic_list_concat(List, /, Atom).
 1437
 1438'$segments_to_list'(A/B, H, T) :-
 1439    '$segments_to_list'(A, H, T0),
 1440    '$segments_to_list'(B, T0, T).
 1441'$segments_to_list'(A, [A|T], T) :-
 1442    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.

 1452'$relative_to'(Conditions, Default, Dir) :-
 1453    (   '$option'(relative_to(FileOrDir), Conditions)
 1454    *-> (   exists_directory(FileOrDir)
 1455	->  Dir = FileOrDir
 1456	;   atom_concat(Dir, /, FileOrDir)
 1457	->  true
 1458	;   file_directory_name(FileOrDir, Dir)
 1459	)
 1460    ;   Default == cwd
 1461    ->  '$cwd'(Dir)
 1462    ;   Default == source
 1463    ->  source_location(ContextFile, _Line),
 1464	file_directory_name(ContextFile, Dir)
 1465    ).

 $chk_alias_file(+Spec, +Exts, +Cond, +Cache, +CWD, -FullFile) is nondet

 1470:- dynamic
 1471    '$search_path_file_cache'/3,    % SHA1, Time, Path
 1472    '$search_path_gc_time'/1.       % Time
 1473:- volatile
 1474    '$search_path_file_cache'/3,
 1475    '$search_path_gc_time'/1. 1476:- '$notransact'(('$search_path_file_cache'/3,
 1477                  '$search_path_gc_time'/1)). 1478
 1479:- create_prolog_flag(file_search_cache_time, 10, []). 1480
 1481'$chk_alias_file'(Spec, Exts, Cond, true, CWD, FullFile) :-
 1482    !,
 1483    findall(Exp, '$expand_file_search_path'(Spec, Exp, Cond), Expansions),
 1484    current_prolog_flag(emulated_dialect, Dialect),
 1485    Cache = cache(Exts, Cond, CWD, Expansions, Dialect),
 1486    variant_sha1(Spec+Cache, SHA1),
 1487    get_time(Now),
 1488    current_prolog_flag(file_search_cache_time, TimeOut),
 1489    (   '$search_path_file_cache'(SHA1, CachedTime, FullFile),
 1490	CachedTime > Now - TimeOut,
 1491	'$file_conditions'(Cond, FullFile)
 1492    ->  '$search_message'(file_search(cache(Spec, Cond), FullFile))
 1493    ;   '$member'(Expanded, Expansions),
 1494	'$extend_file'(Expanded, Exts, LibFile),
 1495	(   '$file_conditions'(Cond, LibFile),
 1496	    '$absolute_file_name'(LibFile, FullFile),
 1497	    '$cache_file_found'(SHA1, Now, TimeOut, FullFile)
 1498	->  '$search_message'(file_search(found(Spec, Cond), FullFile))
 1499	;   '$search_message'(file_search(tried(Spec, Cond), LibFile)),
 1500	    fail
 1501	)
 1502    ).
 1503'$chk_alias_file'(Spec, Exts, Cond, false, _CWD, FullFile) :-
 1504    '$expand_file_search_path'(Spec, Expanded, Cond),
 1505    '$extend_file'(Expanded, Exts, LibFile),
 1506    '$file_conditions'(Cond, LibFile),
 1507    '$absolute_file_name'(LibFile, FullFile).
 1508
 1509'$cache_file_found'(_, _, TimeOut, _) :-
 1510    TimeOut =:= 0,
 1511    !.
 1512'$cache_file_found'(SHA1, Now, TimeOut, FullFile) :-
 1513    '$search_path_file_cache'(SHA1, Saved, FullFile),
 1514    !,
 1515    (   Now - Saved < TimeOut/2
 1516    ->  true
 1517    ;   retractall('$search_path_file_cache'(SHA1, _, _)),
 1518	asserta('$search_path_file_cache'(SHA1, Now, FullFile))
 1519    ).
 1520'$cache_file_found'(SHA1, Now, TimeOut, FullFile) :-
 1521    'gc_file_search_cache'(TimeOut),
 1522    asserta('$search_path_file_cache'(SHA1, Now, FullFile)).
 1523
 1524'gc_file_search_cache'(TimeOut) :-
 1525    get_time(Now),
 1526    '$search_path_gc_time'(Last),
 1527    Now-Last < TimeOut/2,
 1528    !.
 1529'gc_file_search_cache'(TimeOut) :-
 1530    get_time(Now),
 1531    retractall('$search_path_gc_time'(_)),
 1532    assertz('$search_path_gc_time'(Now)),
 1533    Before is Now - TimeOut,
 1534    (   '$search_path_file_cache'(SHA1, Cached, FullFile),
 1535	Cached < Before,
 1536	retractall('$search_path_file_cache'(SHA1, Cached, FullFile)),
 1537	fail
 1538    ;   true
 1539    ).
 1540
 1541
 1542'$search_message'(Term) :-
 1543    current_prolog_flag(verbose_file_search, true),
 1544    !,
 1545    print_message(informational, Term).
 1546'$search_message'(_).

 $file_conditions(+Condition, +Path)

Verify Path satisfies Condition.

 1553'$file_conditions'(List, File) :-
 1554    is_list(List),
 1555    !,
 1556    \+ ( '$member'(C, List),
 1557	 '$file_condition'(C),
 1558	 \+ '$file_condition'(C, File)
 1559       ).
 1560'$file_conditions'(Map, File) :-
 1561    \+ (  get_dict(Key, Map, Value),
 1562	  C =.. [Key,Value],
 1563	  '$file_condition'(C),
 1564	 \+ '$file_condition'(C, File)
 1565       ).
 1566
 1567'$file_condition'(file_type(directory), File) :-
 1568    !,
 1569    exists_directory(File).
 1570'$file_condition'(file_type(_), File) :-
 1571    !,
 1572    \+ exists_directory(File).
 1573'$file_condition'(access(Accesses), File) :-
 1574    !,
 1575    \+ (  '$one_or_member'(Access, Accesses),
 1576	  \+ access_file(File, Access)
 1577       ).
 1578
 1579'$file_condition'(exists).
 1580'$file_condition'(file_type(_)).
 1581'$file_condition'(access(_)).
 1582
 1583'$extend_file'(File, Exts, FileEx) :-
 1584    '$ensure_extensions'(Exts, File, Fs),
 1585    '$list_to_set'(Fs, FsSet),
 1586    '$member'(FileEx, FsSet).
 1587
 1588'$ensure_extensions'([], _, []).
 1589'$ensure_extensions'([E|E0], F, [FE|E1]) :-
 1590    file_name_extension(F, E, FE),
 1591    '$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).

 1598'$list_to_set'(List, Set) :-
 1599    '$number_list'(List, 1, Numbered),
 1600    sort(1, @=<, Numbered, ONum),
 1601    '$remove_dup_keys'(ONum, NumSet),
 1602    sort(2, @=<, NumSet, ONumSet),
 1603    '$pairs_keys'(ONumSet, Set).
 1604
 1605'$number_list'([], _, []).
 1606'$number_list'([H|T0], N, [H-N|T]) :-
 1607    N1 is N+1,
 1608    '$number_list'(T0, N1, T).
 1609
 1610'$remove_dup_keys'([], []).
 1611'$remove_dup_keys'([H|T0], [H|T]) :-
 1612    H = V-_,
 1613    '$remove_same_key'(T0, V, T1),
 1614    '$remove_dup_keys'(T1, T).
 1615
 1616'$remove_same_key'([V1-_|T0], V, T) :-
 1617    V1 == V,
 1618    !,
 1619    '$remove_same_key'(T0, V, T).
 1620'$remove_same_key'(L, _, L).
 1621
 1622'$pairs_keys'([], []).
 1623'$pairs_keys'([K-_|T0], [K|T]) :-
 1624    '$pairs_keys'(T0, T).
 1625
 1626'$pairs_values'([], []).
 1627'$pairs_values'([_-V|T0], [V|T]) :-
 1628    '$pairs_values'(T0, T).
 1629
 1630/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 1631Canonicalise the extension list. Old SWI-Prolog   require  `.pl', etc, which
 1632the Quintus compatibility  requests  `pl'.   This  layer  canonicalises  all
 1633extensions to .ext
 1634- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 1635
 1636'$canonicalise_extensions'([], []) :- !.
 1637'$canonicalise_extensions'([H|T], [CH|CT]) :-
 1638    !,
 1639    '$must_be'(atom, H),
 1640    '$canonicalise_extension'(H, CH),
 1641    '$canonicalise_extensions'(T, CT).
 1642'$canonicalise_extensions'(E, [CE]) :-
 1643    '$canonicalise_extension'(E, CE).
 1644
 1645'$canonicalise_extension'('', '') :- !.
 1646'$canonicalise_extension'(DotAtom, DotAtom) :-
 1647    sub_atom(DotAtom, 0, _, _, '.'),
 1648    !.
 1649'$canonicalise_extension'(Atom, DotAtom) :-
 1650    atom_concat('.', Atom, DotAtom).
 1651
 1652
 1653		/********************************
 1654		*            CONSULT            *
 1655		*********************************/
 1656
 1657:- dynamic
 1658    user:library_directory/1,
 1659    user:prolog_load_file/2. 1660:- multifile
 1661    user:library_directory/1,
 1662    user:prolog_load_file/2. 1663
 1664:- prompt(_, '|: '). 1665
 1666:- thread_local
 1667    '$compilation_mode_store'/1,    % database, wic, qlf
 1668    '$directive_mode_store'/1.      % database, wic, qlf
 1669:- volatile
 1670    '$compilation_mode_store'/1,
 1671    '$directive_mode_store'/1. 1672:- '$notransact'(('$compilation_mode_store'/1,
 1673                  '$directive_mode_store'/1)). 1674
 1675'$compilation_mode'(Mode) :-
 1676    (   '$compilation_mode_store'(Val)
 1677    ->  Mode = Val
 1678    ;   Mode = database
 1679    ).
 1680
 1681'$set_compilation_mode'(Mode) :-
 1682    retractall('$compilation_mode_store'(_)),
 1683    assertz('$compilation_mode_store'(Mode)).
 1684
 1685'$compilation_mode'(Old, New) :-
 1686    '$compilation_mode'(Old),
 1687    (   New == Old
 1688    ->  true
 1689    ;   '$set_compilation_mode'(New)
 1690    ).
 1691
 1692'$directive_mode'(Mode) :-
 1693    (   '$directive_mode_store'(Val)
 1694    ->  Mode = Val
 1695    ;   Mode = database
 1696    ).
 1697
 1698'$directive_mode'(Old, New) :-
 1699    '$directive_mode'(Old),
 1700    (   New == Old
 1701    ->  true
 1702    ;   '$set_directive_mode'(New)
 1703    ).
 1704
 1705'$set_directive_mode'(Mode) :-
 1706    retractall('$directive_mode_store'(_)),
 1707    assertz('$directive_mode_store'(Mode)).