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(path_sep, Sep),
 1077    atomic_list_concat(Dirs, Sep, Path),
 1078    '$member'(Dir, Dirs).
 1079user:file_search_path(user_app_data, Dir) :-
 1080    '$xdg_prolog_directory'(data, Dir).
 1081user:file_search_path(common_app_data, Dir) :-
 1082    '$xdg_prolog_directory'(common_data, Dir).
 1083user:file_search_path(user_app_config, Dir) :-
 1084    '$xdg_prolog_directory'(config, Dir).
 1085user:file_search_path(common_app_config, Dir) :-
 1086    '$xdg_prolog_directory'(common_config, Dir).
 1087user:file_search_path(app_data, user_app_data('.')).
 1088user:file_search_path(app_data, common_app_data('.')).
 1089user:file_search_path(app_config, user_app_config('.')).
 1090user:file_search_path(app_config, common_app_config('.')).
 1091% backward compatibility
 1092user:file_search_path(app_preferences, user_app_config('.')).
 1093user:file_search_path(user_profile, app_preferences('.')).
 1094user:file_search_path(app, swi(app)).
 1095user:file_search_path(app, app_data(app)).
 1096
 1097'$xdg_prolog_directory'(Which, Dir) :-
 1098    '$xdg_directory'(Which, XDGDir),
 1099    '$make_config_dir'(XDGDir),
 1100    '$ensure_slash'(XDGDir, XDGDirS),
 1101    atom_concat(XDGDirS, 'swi-prolog', Dir),
 1102    '$make_config_dir'(Dir).
 1103
 1104'$xdg_directory'(Which, Dir) :-
 1105    '$xdg_directory_search'(Where),
 1106    '$xdg_directory'(Which, Where, Dir).
 1107
 1108'$xdg_directory_search'(xdg) :-
 1109    current_prolog_flag(xdg, true),
 1110    !.
 1111'$xdg_directory_search'(Where) :-
 1112    current_prolog_flag(windows, true),
 1113    (   current_prolog_flag(xdg, false)
 1114    ->  Where = windows
 1115    ;   '$member'(Where, [windows, xdg])
 1116    ).
 1117
 1118% config
 1119'$xdg_directory'(config, windows, Home) :-
 1120    catch(win_folder(appdata, Home), _, fail).
 1121'$xdg_directory'(config, xdg, Home) :-
 1122    getenv('XDG_CONFIG_HOME', Home).
 1123'$xdg_directory'(config, xdg, Home) :-
 1124    expand_file_name('~/.config', [Home]).
 1125% data
 1126'$xdg_directory'(data, windows, Home) :-
 1127    catch(win_folder(local_appdata, Home), _, fail).
 1128'$xdg_directory'(data, xdg, Home) :-
 1129    getenv('XDG_DATA_HOME', Home).
 1130'$xdg_directory'(data, xdg, Home) :-
 1131    expand_file_name('~/.local', [Local]),
 1132    '$make_config_dir'(Local),
 1133    atom_concat(Local, '/share', Home),
 1134    '$make_config_dir'(Home).
 1135% common data
 1136'$xdg_directory'(common_data, windows, Dir) :-
 1137    catch(win_folder(common_appdata, Dir), _, fail).
 1138'$xdg_directory'(common_data, xdg, Dir) :-
 1139    '$existing_dir_from_env_path'('XDG_DATA_DIRS',
 1140				  [ '/usr/local/share',
 1141				    '/usr/share'
 1142				  ],
 1143				  Dir).
 1144% common config
 1145'$xdg_directory'(common_config, windows, Dir) :-
 1146    catch(win_folder(common_appdata, Dir), _, fail).
 1147'$xdg_directory'(common_config, xdg, Dir) :-
 1148    '$existing_dir_from_env_path'('XDG_CONFIG_DIRS', ['/etc/xdg'], Dir).
 1149
 1150'$existing_dir_from_env_path'(Env, Defaults, Dir) :-
 1151    (   getenv(Env, Path)
 1152    ->  current_prolog_flag(path_sep, Sep),
 1153	atomic_list_concat(Dirs, Sep, Path)
 1154    ;   Dirs = Defaults
 1155    ),
 1156    '$member'(Dir, Dirs),
 1157    Dir \== '',
 1158    exists_directory(Dir).
 1159
 1160'$make_config_dir'(Dir) :-
 1161    exists_directory(Dir),
 1162    !.
 1163'$make_config_dir'(Dir) :-
 1164    nb_current('$create_search_directories', true),
 1165    file_directory_name(Dir, Parent),
 1166    '$my_file'(Parent),
 1167    catch(make_directory(Dir), _, fail).
 1168
 1169'$ensure_slash'(Dir, DirS) :-
 1170    (   sub_atom(Dir, _, _, 0, /)
 1171    ->  DirS = Dir
 1172    ;   atom_concat(Dir, /, DirS)
 1173    ).
 1174
 1175:- dynamic '$ext_lib_dirs'/1. 1176:- volatile '$ext_lib_dirs'/1. 1177
 1178'$ext_library_directory'(Dir) :-
 1179    '$ext_lib_dirs'(Dirs),
 1180    !,
 1181    '$member'(Dir, Dirs).
 1182'$ext_library_directory'(Dir) :-
 1183    current_prolog_flag(home, Home),
 1184    atom_concat(Home, '/library/ext/*', Pattern),
 1185    expand_file_name(Pattern, Dirs0),
 1186    '$include'(exists_directory, Dirs0, Dirs),
 1187    asserta('$ext_lib_dirs'(Dirs)),
 1188    '$member'(Dir, Dirs).

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

 1193'$expand_file_search_path'(Spec, Expanded, Cond) :-
 1194    '$option'(access(Access), Cond),
 1195    memberchk(Access, [write,append]),
 1196    !,
 1197    setup_call_cleanup(
 1198	nb_setval('$create_search_directories', true),
 1199	expand_file_search_path(Spec, Expanded),
 1200	nb_delete('$create_search_directories')).
 1201'$expand_file_search_path'(Spec, Expanded, _Cond) :-
 1202    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?

 1210expand_file_search_path(Spec, Expanded) :-
 1211    catch('$expand_file_search_path'(Spec, Expanded, 0, []),
 1212	  loop(Used),
 1213	  throw(error(loop_error(Spec), file_search(Used)))).
 1214
 1215'$expand_file_search_path'(Spec, Expanded, N, Used) :-
 1216    functor(Spec, Alias, 1),
 1217    !,
 1218    user:file_search_path(Alias, Exp0),
 1219    NN is N + 1,
 1220    (   NN > 16
 1221    ->  throw(loop(Used))
 1222    ;   true
 1223    ),
 1224    '$expand_file_search_path'(Exp0, Exp1, NN, [Alias=Exp0|Used]),
 1225    arg(1, Spec, Segments),
 1226    '$segments_to_atom'(Segments, File),
 1227    '$make_path'(Exp1, File, Expanded).
 1228'$expand_file_search_path'(Spec, Path, _, _) :-
 1229    '$segments_to_atom'(Spec, Path).
 1230
 1231'$make_path'(Dir, '.', Path) :-
 1232    !,
 1233    Path = Dir.
 1234'$make_path'(Dir, File, Path) :-
 1235    sub_atom(Dir, _, _, 0, /),
 1236    !,
 1237    atom_concat(Dir, File, Path).
 1238'$make_path'(Dir, File, Path) :-
 1239    atomic_list_concat([Dir, /, File], Path).
 1240
 1241
 1242		/********************************
 1243		*         FILE CHECKING         *
 1244		*********************************/

 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.

 1255absolute_file_name(Spec, Options, Path) :-
 1256    '$is_options'(Options),
 1257    \+ '$is_options'(Path),
 1258    !,
 1259    '$absolute_file_name'(Spec, Path, Options).
 1260absolute_file_name(Spec, Path, Options) :-
 1261    '$absolute_file_name'(Spec, Path, Options).
 1262
 1263'$absolute_file_name'(Spec, Path, Options0) :-
 1264    '$options_dict'(Options0, Options),
 1265		    % get the valid extensions
 1266    (   '$select_option'(extensions(Exts), Options, Options1)
 1267    ->  '$must_be'(list, Exts)
 1268    ;   '$option'(file_type(Type), Options)
 1269    ->  '$must_be'(atom, Type),
 1270	'$file_type_extensions'(Type, Exts),
 1271	Options1 = Options
 1272    ;   Options1 = Options,
 1273	Exts = ['']
 1274    ),
 1275    '$canonicalise_extensions'(Exts, Extensions),
 1276		    % unless specified otherwise, ask regular file
 1277    (   (   nonvar(Type)
 1278	;   '$option'(access(none), Options, none)
 1279	)
 1280    ->  Options2 = Options1
 1281    ;   '$merge_options'(_{file_type:regular}, Options1, Options2)
 1282    ),
 1283		    % Det or nondet?
 1284    (   '$select_option'(solutions(Sols), Options2, Options3)
 1285    ->  '$must_be'(oneof(atom, solutions, [first,all]), Sols)
 1286    ;   Sols = first,
 1287	Options3 = Options2
 1288    ),
 1289		    % Errors or not?
 1290    (   '$select_option'(file_errors(FileErrors), Options3, Options4)
 1291    ->  '$must_be'(oneof(atom, file_errors, [error,fail]), FileErrors)
 1292    ;   FileErrors = error,
 1293	Options4 = Options3
 1294    ),
 1295		    % Expand shell patterns?
 1296    (   atomic(Spec),
 1297	'$select_option'(expand(Expand), Options4, Options5),
 1298	'$must_be'(boolean, Expand)
 1299    ->  expand_file_name(Spec, List),
 1300	'$member'(Spec1, List)
 1301    ;   Spec1 = Spec,
 1302	Options5 = Options4
 1303    ),
 1304		    % Search for files
 1305    (   Sols == first
 1306    ->  (   '$chk_file'(Spec1, Extensions, Options5, true, Path)
 1307	->  !       % also kill choice point of expand_file_name/2
 1308	;   (   FileErrors == fail
 1309	    ->  fail
 1310	    ;   '$current_module'('$bags', _File),
 1311		findall(P,
 1312			'$chk_file'(Spec1, Extensions, [access(exist)],
 1313				    false, P),
 1314			Candidates),
 1315		'$abs_file_error'(Spec, Candidates, Options5)
 1316	    )
 1317	)
 1318    ;   '$chk_file'(Spec1, Extensions, Options5, false, Path)
 1319    ).
 1320
 1321'$abs_file_error'(Spec, Candidates, Conditions) :-
 1322    '$member'(F, Candidates),
 1323    '$member'(C, Conditions),
 1324    '$file_condition'(C),
 1325    '$file_error'(C, Spec, F, E, Comment),
 1326    !,
 1327    throw(error(E, context(_, Comment))).
 1328'$abs_file_error'(Spec, _, _) :-
 1329    '$existence_error'(source_sink, Spec).
 1330
 1331'$file_error'(file_type(directory), Spec, File, Error, Comment) :-
 1332    \+ exists_directory(File),
 1333    !,
 1334    Error = existence_error(directory, Spec),
 1335    Comment = not_a_directory(File).
 1336'$file_error'(file_type(_), Spec, File, Error, Comment) :-
 1337    exists_directory(File),
 1338    !,
 1339    Error = existence_error(file, Spec),
 1340    Comment = directory(File).
 1341'$file_error'(access(OneOrList), Spec, File, Error, _) :-
 1342    '$one_or_member'(Access, OneOrList),
 1343    \+ access_file(File, Access),
 1344    Error = permission_error(Access, source_sink, Spec).
 1345
 1346'$one_or_member'(Elem, List) :-
 1347    is_list(List),
 1348    !,
 1349    '$member'(Elem, List).
 1350'$one_or_member'(Elem, Elem).
 1351
 1352
 1353'$file_type_extensions'(source, Exts) :-       % SICStus 3.9 compatibility
 1354    !,
 1355    '$file_type_extensions'(prolog, Exts).
 1356'$file_type_extensions'(Type, Exts) :-
 1357    '$current_module'('$bags', _File),
 1358    !,
 1359    findall(Ext, user:prolog_file_type(Ext, Type), Exts0),
 1360    (   Exts0 == [],
 1361	\+ '$ft_no_ext'(Type)
 1362    ->  '$domain_error'(file_type, Type)
 1363    ;   true
 1364    ),
 1365    '$append'(Exts0, [''], Exts).
 1366'$file_type_extensions'(prolog, [pl, '']). % findall is not yet defined ...
 1367
 1368'$ft_no_ext'(txt).
 1369'$ft_no_ext'(executable).
 1370'$ft_no_ext'(directory).
 1371'$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.

 1384:- multifile(user:prolog_file_type/2). 1385:- dynamic(user:prolog_file_type/2). 1386
 1387user:prolog_file_type(pl,       prolog).
 1388user:prolog_file_type(prolog,   prolog).
 1389user:prolog_file_type(qlf,      prolog).
 1390user:prolog_file_type(qlf,      qlf).
 1391user:prolog_file_type(Ext,      executable) :-
 1392    current_prolog_flag(shared_object_extension, Ext).
 1393user:prolog_file_type(dylib,    executable) :-
 1394    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.

 1401'$chk_file'(Spec, _Extensions, _Cond, _Cache, _FullName) :-
 1402    \+ ground(Spec),
 1403    !,
 1404    '$instantiation_error'(Spec).
 1405'$chk_file'(Spec, Extensions, Cond, Cache, FullName) :-
 1406    compound(Spec),
 1407    functor(Spec, _, 1),
 1408    !,
 1409    '$relative_to'(Cond, cwd, CWD),
 1410    '$chk_alias_file'(Spec, Extensions, Cond, Cache, CWD, FullName).
 1411'$chk_file'(Segments, Ext, Cond, Cache, FullName) :-    % allow a/b/...
 1412    \+ atomic(Segments),
 1413    !,
 1414    '$segments_to_atom'(Segments, Atom),
 1415    '$chk_file'(Atom, Ext, Cond, Cache, FullName).
 1416'$chk_file'(File, Exts, Cond, _, FullName) :-
 1417    is_absolute_file_name(File),
 1418    !,
 1419    '$extend_file'(File, Exts, Extended),
 1420    '$file_conditions'(Cond, Extended),
 1421    '$absolute_file_name'(Extended, FullName).
 1422'$chk_file'(File, Exts, Cond, _, FullName) :-
 1423    '$relative_to'(Cond, source, Dir),
 1424    atomic_list_concat([Dir, /, File], AbsFile),
 1425    '$extend_file'(AbsFile, Exts, Extended),
 1426    '$file_conditions'(Cond, Extended),
 1427    !,
 1428    '$absolute_file_name'(Extended, FullName).
 1429'$chk_file'(File, Exts, Cond, _, FullName) :-
 1430    '$extend_file'(File, Exts, Extended),
 1431    '$file_conditions'(Cond, Extended),
 1432    '$absolute_file_name'(Extended, FullName).
 1433
 1434'$segments_to_atom'(Atom, Atom) :-
 1435    atomic(Atom),
 1436    !.
 1437'$segments_to_atom'(Segments, Atom) :-
 1438    '$segments_to_list'(Segments, List, []),
 1439    !,
 1440    atomic_list_concat(List, /, Atom).
 1441
 1442'$segments_to_list'(A/B, H, T) :-
 1443    '$segments_to_list'(A, H, T0),
 1444    '$segments_to_list'(B, T0, T).
 1445'$segments_to_list'(A, [A|T], T) :-
 1446    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.

 1456'$relative_to'(Conditions, Default, Dir) :-
 1457    (   '$option'(relative_to(FileOrDir), Conditions)
 1458    *-> (   exists_directory(FileOrDir)
 1459	->  Dir = FileOrDir
 1460	;   atom_concat(Dir, /, FileOrDir)
 1461	->  true
 1462	;   file_directory_name(FileOrDir, Dir)
 1463	)
 1464    ;   Default == cwd
 1465    ->  '$cwd'(Dir)
 1466    ;   Default == source
 1467    ->  source_location(ContextFile, _Line),
 1468	file_directory_name(ContextFile, Dir)
 1469    ).

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

 1474:- dynamic
 1475    '$search_path_file_cache'/3,    % SHA1, Time, Path
 1476    '$search_path_gc_time'/1.       % Time
 1477:- volatile
 1478    '$search_path_file_cache'/3,
 1479    '$search_path_gc_time'/1. 1480:- '$notransact'(('$search_path_file_cache'/3,
 1481                  '$search_path_gc_time'/1)). 1482
 1483:- create_prolog_flag(file_search_cache_time, 10, []). 1484
 1485'$chk_alias_file'(Spec, Exts, Cond, true, CWD, FullFile) :-
 1486    !,
 1487    findall(Exp, '$expand_file_search_path'(Spec, Exp, Cond), Expansions),
 1488    current_prolog_flag(emulated_dialect, Dialect),
 1489    Cache = cache(Exts, Cond, CWD, Expansions, Dialect),
 1490    variant_sha1(Spec+Cache, SHA1),
 1491    get_time(Now),
 1492    current_prolog_flag(file_search_cache_time, TimeOut),
 1493    (   '$search_path_file_cache'(SHA1, CachedTime, FullFile),
 1494	CachedTime > Now - TimeOut,
 1495	'$file_conditions'(Cond, FullFile)
 1496    ->  '$search_message'(file_search(cache(Spec, Cond), FullFile))
 1497    ;   '$member'(Expanded, Expansions),
 1498	'$extend_file'(Expanded, Exts, LibFile),
 1499	(   '$file_conditions'(Cond, LibFile),
 1500	    '$absolute_file_name'(LibFile, FullFile),
 1501	    '$cache_file_found'(SHA1, Now, TimeOut, FullFile)
 1502	->  '$search_message'(file_search(found(Spec, Cond), FullFile))
 1503	;   '$search_message'(file_search(tried(Spec, Cond), LibFile)),
 1504	    fail
 1505	)
 1506    ).
 1507'$chk_alias_file'(Spec, Exts, Cond, false, _CWD, FullFile) :-
 1508    '$expand_file_search_path'(Spec, Expanded, Cond),
 1509    '$extend_file'(Expanded, Exts, LibFile),
 1510    '$file_conditions'(Cond, LibFile),
 1511    '$absolute_file_name'(LibFile, FullFile).
 1512
 1513'$cache_file_found'(_, _, TimeOut, _) :-
 1514    TimeOut =:= 0,
 1515    !.
 1516'$cache_file_found'(SHA1, Now, TimeOut, FullFile) :-
 1517    '$search_path_file_cache'(SHA1, Saved, FullFile),
 1518    !,
 1519    (   Now - Saved < TimeOut/2
 1520    ->  true
 1521    ;   retractall('$search_path_file_cache'(SHA1, _, _)),
 1522	asserta('$search_path_file_cache'(SHA1, Now, FullFile))
 1523    ).
 1524'$cache_file_found'(SHA1, Now, TimeOut, FullFile) :-
 1525    'gc_file_search_cache'(TimeOut),
 1526    asserta('$search_path_file_cache'(SHA1, Now, FullFile)).
 1527
 1528'gc_file_search_cache'(TimeOut) :-
 1529    get_time(Now),
 1530    '$search_path_gc_time'(Last),
 1531    Now-Last < TimeOut/2,
 1532    !.
 1533'gc_file_search_cache'(TimeOut) :-
 1534    get_time(Now),
 1535    retractall('$search_path_gc_time'(_)),
 1536    assertz('$search_path_gc_time'(Now)),
 1537    Before is Now - TimeOut,
 1538    (   '$search_path_file_cache'(SHA1, Cached, FullFile),
 1539	Cached < Before,
 1540	retractall('$search_path_file_cache'(SHA1, Cached, FullFile)),
 1541	fail
 1542    ;   true
 1543    ).
 1544
 1545
 1546'$search_message'(Term) :-
 1547    current_prolog_flag(verbose_file_search, true),
 1548    !,
 1549    print_message(informational, Term).
 1550'$search_message'(_).

 $file_conditions(+Condition, +Path)

Verify Path satisfies Condition.

 1557'$file_conditions'(List, File) :-
 1558    is_list(List),
 1559    !,
 1560    \+ ( '$member'(C, List),
 1561	 '$file_condition'(C),
 1562	 \+ '$file_condition'(C, File)
 1563       ).
 1564'$file_conditions'(Map, File) :-
 1565    \+ (  get_dict(Key, Map, Value),
 1566	  C =.. [Key,Value],
 1567	  '$file_condition'(C),
 1568	 \+ '$file_condition'(C, File)
 1569       ).
 1570
 1571'$file_condition'(file_type(directory), File) :-
 1572    !,
 1573    exists_directory(File).
 1574'$file_condition'(file_type(_), File) :-
 1575    !,
 1576    \+ exists_directory(File).
 1577'$file_condition'(access(Accesses), File) :-
 1578    !,
 1579    \+ (  '$one_or_member'(Access, Accesses),
 1580	  \+ access_file(File, Access)
 1581       ).
 1582
 1583'$file_condition'(exists).
 1584'$file_condition'(file_type(_)).
 1585'$file_condition'(access(_)).
 1586
 1587'$extend_file'(File, Exts, FileEx) :-
 1588    '$ensure_extensions'(Exts, File, Fs),
 1589    '$list_to_set'(Fs, FsSet),
 1590    '$member'(FileEx, FsSet).
 1591
 1592'$ensure_extensions'([], _, []).
 1593'$ensure_extensions'([E|E0], F, [FE|E1]) :-
 1594    file_name_extension(F, E, FE),
 1595    '$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).

 1602'$list_to_set'(List, Set) :-
 1603    '$number_list'(List, 1, Numbered),
 1604    sort(1, @=<, Numbered, ONum),
 1605    '$remove_dup_keys'(ONum, NumSet),
 1606    sort(2, @=<, NumSet, ONumSet),
 1607    '$pairs_keys'(ONumSet, Set).
 1608
 1609'$number_list'([], _, []).
 1610'$number_list'([H|T0], N, [H-N|T]) :-
 1611    N1 is N+1,
 1612    '$number_list'(T0, N1, T).
 1613
 1614'$remove_dup_keys'([], []).
 1615'$remove_dup_keys'([H|T0], [H|T]) :-
 1616    H = V-_,
 1617    '$remove_same_key'(T0, V, T1),
 1618    '$remove_dup_keys'(T1, T).
 1619
 1620'$remove_same_key'([V1-_|T0], V, T) :-
 1621    V1 == V,
 1622    !,
 1623    '$remove_same_key'(T0, V, T).
 1624'$remove_same_key'(L, _, L).
 1625
 1626'$pairs_keys'([], []).
 1627'$pairs_keys'([K-_|T0], [K|T]) :-
 1628    '$pairs_keys'(T0, T).
 1629
 1630'$pairs_values'([], []).
 1631'$pairs_values'([_-V|T0], [V|T]) :-
 1632    '$pairs_values'(T0, T).
 1633
 1634/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 1635Canonicalise the extension list. Old SWI-Prolog   require  `.pl', etc, which
 1636the Quintus compatibility  requests  `pl'.   This  layer  canonicalises  all
 1637extensions to .ext
 1638- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 1639
 1640'$canonicalise_extensions'([], []) :- !.
 1641'$canonicalise_extensions'([H|T], [CH|CT]) :-
 1642    !,
 1643    '$must_be'(atom, H),
 1644    '$canonicalise_extension'(H, CH),
 1645    '$canonicalise_extensions'(T, CT).
 1646'$canonicalise_extensions'(E, [CE]) :-
 1647    '$canonicalise_extension'(E, CE).
 1648
 1649'$canonicalise_extension'('', '') :- !.
 1650'$canonicalise_extension'(DotAtom, DotAtom) :-
 1651    sub_atom(DotAtom, 0, _, _, '.'),
 1652    !.
 1653'$canonicalise_extension'(Atom, DotAtom) :-
 1654    atom_concat('.', Atom, DotAtom).
 1655
 1656
 1657		/********************************
 1658		*            CONSULT            *
 1659		*********************************/
 1660
 1661:- dynamic
 1662    user:library_directory/1,
 1663    user:prolog_load_file/2. 1664:- multifile
 1665    user:library_directory/1,
 1666    user:prolog_load_file/2. 1667
 1668:- prompt(_, '|: '). 1669
 1670:- thread_local
 1671    '$compilation_mode_store'/1,    % database, wic, qlf
 1672    '$directive_mode_store'/1.      % database, wic, qlf
 1673:- volatile
 1674    '$compilation_mode_store'/1,
 1675    '$directive_mode_store'/1. 1676:- '$notransact'(('$compilation_mode_store'/1,
 1677                  '$directive_mode_store'/1)). 1678
 1679'$compilation_mode'(Mode) :-
 1680    (   '$compilation_mode_store'(Val)
 1681    ->  Mode = Val
 1682    ;   Mode = database
 1683    ).
 1684
 1685'$set_compilation_mode'(Mode) :-
 1686    retractall('$compilation_mode_store'(_)),
 1687    assertz('$compilation_mode_store'(Mode)).
 1688
 1689'$compilation_mode'(Old, New) :-
 1690    '$compilation_mode'(Old),
 1691    (   New == Old
 1692    ->  true
 1693    ;   '$set_compilation_mode'(New)
 1694    ).
 1695
 1696'$directive_mode'(Mode) :-
 1697    (   '$directive_mode_store'(Val)
 1698    ->  Mode = Val
 1699    ;   Mode = database
 1700    ).
 1701
 1702'$directive_mode'(Old, New) :-
 1703    '$directive_mode'(Old),
 1704    (   New == Old
 1705    ->  true
 1706    ;   '$set_directive_mode'(New)
 1707    ).
 1708
 1709'$set_directive_mode'(Mode) :-
 1710    retractall('$directive_mode_store'(_)),
 1711    assertz('$directive_mode_store'(Mode)).