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)  1985-2026, University of Amsterdam
    7                              VU University Amsterdam
    8                              SWI-Prolog Solutions b.v.
    9    All rights reserved.
   10
   11    Redistribution and use in source and binary forms, with or without
   12    modification, are permitted provided that the following conditions
   13    are met:
   14
   15    1. Redistributions of source code must retain the above copyright
   16       notice, this list of conditions and the following disclaimer.
   17
   18    2. Redistributions in binary form must reproduce the above copyright
   19       notice, this list of conditions and the following disclaimer in
   20       the documentation and/or other materials provided with the
   21       distribution.
   22
   23    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   24    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   25    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   26    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   27    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   28    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   29    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   30    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   31    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   33    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   34    POSSIBILITY OF SUCH DAMAGE.
   35*/
   36
   37:- module('$toplevel',
   38          [ '$initialise'/0,            % start Prolog
   39            '$toplevel'/0,              % Prolog top-level (re-entrant)
   40            '$compile'/0,               % `-c' toplevel
   41            '$config'/0,                % --dump-runtime-variables toplevel
   42            initialize/0,               % Run program initialization
   43            version/0,                  % Write initial banner
   44            version/1,                  % Add message to the banner
   45            prolog/0,                   % user toplevel predicate
   46            '$query_loop'/0,            % toplevel predicate
   47            '$execute_query'/3,         % +Query, +Bindings, -Truth
   48            residual_goals/1,           % +Callable
   49            (initialization)/1,         % initialization goal (directive)
   50            '$thread_init'/0,           % initialise thread
   51            (thread_initialization)/1   % thread initialization goal
   52            ]).   53
   54
   55                 /*******************************
   56                 *         VERSION BANNER       *
   57                 *******************************/
   58
   59:- dynamic prolog:version_msg/1.   60:- multifile prolog:version_msg/1.

 version is det

Print the Prolog banner message and messages registered using version/1.

   67version :-
   68    print_message(banner, welcome).

 version(+Message) is det

Add message to version/0

   74:- multifile
   75    system:term_expansion/2.   76
   77system:term_expansion((:- version(Message)),
   78                      prolog:version_msg(Message)).
   79
   80version(Message) :-
   81    (   prolog:version_msg(Message)
   82    ->  true
   83    ;   assertz(prolog:version_msg(Message))
   84    ).
   85
   86
   87                /********************************
   88                *         INITIALISATION        *
   89                *********************************/

 load_init_file(+ScriptMode) is det

Load the user customization file. This can be done using swipl -f file or simply using swipl. In the first case we search the file both directly and over the alias user_app_config. In the latter case we only use the alias.

   98load_init_file(_) :-
   99    '$cmd_option_val'(init_file, OsFile),
  100    !,
  101    prolog_to_os_filename(File, OsFile),
  102    load_init_file(File, explicit).
  103load_init_file(prolog) :-
  104    !,
  105    load_init_file('init.pl', implicit).
  106load_init_file(none) :-
  107    !,
  108    load_init_file('init.pl', implicit).
  109load_init_file(_).

 loaded_init_file(?Base, ?AbsFile)

Used by prolog_load_context/2 to confirm we are loading a script.

  115:- dynamic
  116    loaded_init_file/2.             % already loaded init files
  117
  118load_init_file(none, _) :- !.
  119load_init_file(Base, _) :-
  120    loaded_init_file(Base, _),
  121    !.
  122load_init_file(InitFile, explicit) :-
  123    exists_file(InitFile),
  124    !,
  125    ensure_loaded(user:InitFile).
  126load_init_file(Base, _) :-
  127    absolute_file_name(user_app_config(Base), InitFile,
  128                       [ access(read),
  129                         file_errors(fail)
  130                       ]),
  131    !,
  132    asserta(loaded_init_file(Base, InitFile)),
  133    load_files(user:InitFile,
  134               [ scope_settings(false)
  135               ]).
  136load_init_file('init.pl', implicit) :-
  137    (   current_prolog_flag(windows, true),
  138        absolute_file_name(user_profile('swipl.ini'), InitFile,
  139                           [ access(read),
  140                             file_errors(fail)
  141                           ])
  142    ;   expand_file_name('~/.swiplrc', [InitFile]),
  143        exists_file(InitFile)
  144    ),
  145    !,
  146    print_message(warning, backcomp(init_file_moved(InitFile))).
  147load_init_file(_, _).
  148
  149'$load_system_init_file' :-
  150    loaded_init_file(system, _),
  151    !.
  152'$load_system_init_file' :-
  153    '$cmd_option_val'(system_init_file, Base),
  154    Base \== none,
  155    current_prolog_flag(home, Home),
  156    file_name_extension(Base, rc, Name),
  157    atomic_list_concat([Home, '/', Name], File),
  158    absolute_file_name(File, Path,
  159                       [ file_type(prolog),
  160                         access(read),
  161                         file_errors(fail)
  162                       ]),
  163    asserta(loaded_init_file(system, Path)),
  164    load_files(user:Path,
  165               [ silent(true),
  166                 scope_settings(false)
  167               ]),
  168    !.
  169'$load_system_init_file'.
  170
  171'$load_script_file' :-
  172    loaded_init_file(script, _),
  173    !.
  174'$load_script_file' :-
  175    '$cmd_option_val'(script_file, OsFiles),
  176    load_script_files(OsFiles).
  177
  178load_script_files([]).
  179load_script_files([OsFile|More]) :-
  180    prolog_to_os_filename(File, OsFile),
  181    (   absolute_file_name(File, Path,
  182                           [ file_type(prolog),
  183                             access(read),
  184                             file_errors(fail)
  185                           ])
  186    ->  asserta(loaded_init_file(script, Path)),
  187        load_files(user:Path),
  188        load_files(user:More)
  189    ;   throw(error(existence_error(script_file, File), _))
  190    ).
  191
  192
  193                 /*******************************
  194                 *       AT_INITIALISATION      *
  195                 *******************************/
  196
  197:- meta_predicate
  198    initialization(0).  199
  200:- '$iso'((initialization)/1).

 initialization :Goal

Runs Goal after loading the file in which this directive appears as well as after restoring a saved state.

See also

- initialization/2

  209initialization(Goal) :-
  210    Goal = _:G,
  211    prolog:initialize_now(G, Use),
  212    !,
  213    print_message(warning, initialize_now(G, Use)),
  214    initialization(Goal, now).
  215initialization(Goal) :-
  216    initialization(Goal, after_load).
  217
  218:- multifile
  219    prolog:initialize_now/2,
  220    prolog:message//1.  221
  222prolog:initialize_now(load_foreign_library(_),
  223                      'use :- use_foreign_library/1 instead').
  224prolog:initialize_now(load_foreign_library(_,_),
  225                      'use :- use_foreign_library/2 instead').
  226
  227prolog:message(initialize_now(Goal, Use)) -->
  228    [ 'Initialization goal ~p will be executed'-[Goal],nl,
  229      'immediately for backward compatibility reasons', nl,
  230      '~w'-[Use]
  231    ].
  232
  233'$run_initialization' :-
  234    '$set_prolog_file_extension',
  235    '$run_initialization'(_, []),
  236    '$thread_init'.

 initialize

Run goals registered with :- initialization(Goal, program).. Stop with an exception if a goal fails or raises an exception.

  243initialize :-
  244    forall('$init_goal'(when(program), Goal, Ctx),
  245           run_initialize(Goal, Ctx)).
  246
  247run_initialize(Goal, Ctx) :-
  248    (   catch(Goal, E, true),
  249        (   var(E)
  250        ->  true
  251        ;   throw(error(initialization_error(E, Goal, Ctx), _))
  252        )
  253    ;   throw(error(initialization_error(failed, Goal, Ctx), _))
  254    ).
  255
  256
  257                 /*******************************
  258                 *     THREAD INITIALIZATION    *
  259                 *******************************/
  260
  261:- meta_predicate
  262    thread_initialization(0).  263:- dynamic
  264    '$at_thread_initialization'/1.

 thread_initialization :Goal

Run Goal now and everytime a new thread is created.

  270thread_initialization(Goal) :-
  271    assert('$at_thread_initialization'(Goal)),
  272    call(Goal),
  273    !.

 $thread_init

Called by start_thread() from pl-thread.c before the thread's goal.

  279'$thread_init' :-
  280    set_prolog_flag(toplevel_thread, false),
  281    (   '$at_thread_initialization'(Goal),
  282        (   call(Goal)
  283        ->  fail
  284        ;   fail
  285        )
  286    ;   true
  287    ).
  288
  289
  290                 /*******************************
  291                 *     FILE SEARCH PATH (-p)    *
  292                 *******************************/

 $set_file_search_paths is det

Process -p PathSpec options.

  298'$set_file_search_paths' :-
  299    '$cmd_option_val'(search_paths, Paths),
  300    (   '$member'(Path, Paths),
  301        atom_chars(Path, Chars),
  302        (   phrase('$search_path'(Name, Aliases), Chars)
  303        ->  '$reverse'(Aliases, Aliases1),
  304            forall('$member'(Alias, Aliases1),
  305                   asserta(user:file_search_path(Name, Alias)))
  306        ;   print_message(error, commandline_arg_type(p, Path))
  307        ),
  308        fail ; true
  309    ).
  310
  311'$search_path'(Name, Aliases) -->
  312    '$string'(NameChars),
  313    [=],
  314    !,
  315    {atom_chars(Name, NameChars)},
  316    '$search_aliases'(Aliases).
  317
  318'$search_aliases'([Alias|More]) -->
  319    '$string'(AliasChars),
  320    path_sep,
  321    !,
  322    { '$make_alias'(AliasChars, Alias) },
  323    '$search_aliases'(More).
  324'$search_aliases'([Alias]) -->
  325    '$string'(AliasChars),
  326    '$eos',
  327    !,
  328    { '$make_alias'(AliasChars, Alias) }.
  329
  330path_sep -->
  331    { current_prolog_flag(path_sep, Sep) },
  332    [Sep].
  333
  334'$string'([]) --> [].
  335'$string'([H|T]) --> [H], '$string'(T).
  336
  337'$eos'([], []).
  338
  339'$make_alias'(Chars, Alias) :-
  340    catch(term_to_atom(Alias, Chars), _, fail),
  341    (   atom(Alias)
  342    ;   functor(Alias, F, 1),
  343        F \== /
  344    ),
  345    !.
  346'$make_alias'(Chars, Alias) :-
  347    atom_chars(Alias, Chars).
  348
  349
  350                 /*******************************
  351                 *   LOADING ASSIOCIATED FILES  *
  352                 *******************************/

 argv_prolog_files(-Files, -ScriptMode) is det

Update the Prolog flag argv, extracting the leading script files. This is called after the C based parser removed Prolog options such as -q, -f none, etc. These options are available through '$cmd_option_val'/2.

Our task is to update the Prolog flag argv and return a list of the files to be loaded. The rules are:

• If we find -- all remaining options must go to argv
• If we find *.pl files, these are added to Files and possibly remaining arguments are "script" arguments.
• If we find an existing file, this is Files and possibly remaining arguments are "script" arguments.
• File we find [search:]name, find search(name) as Prolog file, make this the content of Files and pass the remainder as options to argv.

Arguments:

ScriptMode

- is one of exe Program is a saved state prolog One or more *.pl files on commandline script Single existing file on commandline app [path:]cli-name on commandline none Normal interactive session

  386argv_prolog_files([], exe) :-
  387    current_prolog_flag(saved_program_class, runtime),
  388    !,
  389    clean_argv.
  390argv_prolog_files(Files, ScriptMode) :-
  391    current_prolog_flag(argv, Argv),
  392    no_option_files(Argv, Argv1, Files, ScriptMode),
  393    (   (   nonvar(ScriptMode)
  394        ;   Argv1 == []
  395        )
  396    ->  (   Argv1 \== Argv
  397        ->  set_prolog_flag(argv, Argv1)
  398        ;   true
  399        )
  400    ;   '$usage',
  401        halt(1)
  402    ).
  403
  404no_option_files([--|Argv], Argv, [], ScriptMode) :-
  405    !,
  406    (   ScriptMode = none
  407    ->  true
  408    ;   true
  409    ).
  410no_option_files([Opt|_], _, _, ScriptMode) :-
  411    var(ScriptMode),
  412    sub_atom(Opt, 0, _, _, '-'),
  413    !,
  414    '$usage',
  415    halt(1).
  416no_option_files([OsFile|Argv0], Argv, [File|T], ScriptMode) :-
  417    file_name_extension(_, Ext, OsFile),
  418    user:prolog_file_type(Ext, prolog),
  419    !,
  420    ScriptMode = prolog,
  421    prolog_to_os_filename(File, OsFile),
  422    no_option_files(Argv0, Argv, T, ScriptMode).
  423no_option_files([OsScript|Argv], Argv, [Script], ScriptMode) :-
  424    var(ScriptMode),
  425    !,
  426    prolog_to_os_filename(PlScript, OsScript),
  427    (   exists_file(PlScript)
  428    ->  Script = PlScript,
  429        ScriptMode = script
  430    ;   cli_script(OsScript, Script)
  431    ->  ScriptMode = app,
  432        set_prolog_flag(app_name, OsScript)
  433    ;   '$existence_error'(file, PlScript)
  434    ).
  435no_option_files(Argv, Argv, [], ScriptMode) :-
  436    (   ScriptMode = none
  437    ->  true
  438    ;   true
  439    ).
  440
  441cli_script(CLI, Script) :-
  442    (   sub_atom(CLI, Pre, _, Post, ':')
  443    ->  sub_atom(CLI, 0, Pre, _, SearchPath),
  444        sub_atom(CLI, _, Post, 0, Base),
  445        Spec =.. [SearchPath, Base]
  446    ;   Spec = app(CLI)
  447    ),
  448    absolute_file_name(Spec, Script,
  449                       [ file_type(prolog),
  450                         access(exist),
  451                         file_errors(fail)
  452                       ]).
  453
  454clean_argv :-
  455    (   current_prolog_flag(argv, [--|Argv])
  456    ->  set_prolog_flag(argv, Argv)
  457    ;   true
  458    ).

 win_associated_files(+Files)

If SWI-Prolog is started as <exe> <file>.<ext>, where <ext> is the extension registered for associated files, set the Prolog flag associated_file, switch to the directory holding the file and -if possible- adjust the window title.

  467win_associated_files(Files) :-
  468    (   Files = [File|_]
  469    ->  absolute_file_name(File, AbsFile),
  470        set_prolog_flag(associated_file, AbsFile),
  471        forall(prolog:set_app_file_config(Files), true)
  472    ;   true
  473    ).
  474
  475:- multifile
  476    prolog:set_app_file_config/1.               % +Files

 start_pldoc

If the option --pldoc[=port] is given, load the PlDoc system.

  482start_pldoc :-
  483    '$cmd_option_val'(pldoc_server, Server),
  484    (   Server == ''
  485    ->  call((doc_server(_), doc_browser))
  486    ;   catch(atom_number(Server, Port), _, fail)
  487    ->  call(doc_server(Port))
  488    ;   print_message(error, option_usage(pldoc)),
  489        halt(1)
  490    ).
  491start_pldoc.

 load_associated_files(+Files)

Load Prolog files specified from the commandline.

  498load_associated_files(Files) :-
  499    load_files(user:Files).
  500
  501hkey('HKEY_CURRENT_USER/Software/SWI/Prolog').
  502hkey('HKEY_LOCAL_MACHINE/Software/SWI/Prolog').
  503
  504'$set_prolog_file_extension' :-
  505    current_prolog_flag(windows, true),
  506    hkey(Key),
  507    catch(win_registry_get_value(Key, fileExtension, Ext0),
  508          _, fail),
  509    !,
  510    (   atom_concat('.', Ext, Ext0)
  511    ->  true
  512    ;   Ext = Ext0
  513    ),
  514    (   user:prolog_file_type(Ext, prolog)
  515    ->  true
  516    ;   asserta(user:prolog_file_type(Ext, prolog))
  517    ).
  518'$set_prolog_file_extension'.
  519
  520
  521                /********************************
  522                *        TOPLEVEL GOALS         *
  523                *********************************/

 $initialise is semidet

Called from PL_initialise() to do the Prolog part of the initialization. If an exception occurs, this is printed and '$initialise' fails.

  531'$initialise' :-
  532    catch(initialise_prolog, E, initialise_error(E)).
  533
  534initialise_error(unwind(abort)) :- !.
  535initialise_error(unwind(halt(_))) :- !.
  536initialise_error(E) :-
  537    print_message(error, initialization_exception(E)),
  538    fail.
  539
  540initialise_prolog :-
  541    apply_defines,
  542    init_optimise,
  543    '$run_initialization',
  544    '$load_system_init_file',                   % -F file
  545    set_toplevel,                               % set `toplevel_goal` flag from -t
  546    '$set_file_search_paths',                   % handle -p alias=dir[:dir]*
  547    init_debug_flags,
  548    setup_app,
  549    start_pldoc,                                % handle --pldoc[=port]
  550    main_thread_init.

 main_thread_init

Deal with the Epilog toplevel. If the flag epilog is set and xpce is around, create an epilog window and complete the user part of the initialization in the epilog thread.

  558:- if(current_prolog_flag(threads, true)).  559main_thread_init :-
  560    current_prolog_flag(epilog, true),
  561    thread_self(main),
  562    current_prolog_flag(xpce, true),
  563    exists_source(library(epilog)),
  564    !,
  565    setup_theme,
  566    catch(setup_backtrace, E, print_message(warning, E)),
  567    use_module(library(epilog)),
  568    set_thread(main, class(system)),
  569    call(epilog([ init(user_thread_init),
  570                  main(true)
  571                ])).
  572main_thread_init :-
  573    set_thread(main, class(console)),
  574    setup_theme,
  575    user_thread_init.
  576:- else.  577main_thread_init :-
  578    setup_theme,
  579    user_thread_init.
  580:- endif.

 user_thread_init

Complete the toplevel startup. This may run in a separate thread.

  587user_thread_init :-
  588    opt_attach_packs,
  589    argv_prolog_files(Files, ScriptMode),
  590    load_init_file(ScriptMode),                 % -f file
  591    catch(setup_colors, E, print_message(warning, E)),
  592    win_associated_files(Files),                % swipl-win: cd and update title
  593    '$load_script_file',                        % -s file (may be repeated)
  594    load_associated_files(Files),
  595    '$cmd_option_val'(goals, Goals),            % -g goal (may be repeated)
  596    (   ScriptMode == app
  597    ->  run_program_init,                       % initialization(Goal, program)
  598        run_main_init(true)
  599    ;   Goals == [],
  600        \+ '$init_goal'(when(_), _, _)          % no -g or -t or initialization(program)
  601    ->  version                                 % default interactive run
  602    ;   run_init_goals(Goals),                  % run -g goals
  603        (   load_only                           % used -l to load
  604        ->  version
  605        ;   run_program_init,                   % initialization(Goal, program)
  606            run_main_init(false)                % initialization(Goal, main)
  607        )
  608    ).

 setup_theme

  612:- multifile
  613    prolog:theme/1.  614
  615setup_theme :-
  616    current_prolog_flag(theme, Theme),
  617    exists_source(library(theme/Theme)),
  618    !,
  619    use_module(library(theme/Theme)).
  620setup_theme.

 apply_defines

Handle -Dflag[=value] options

  626apply_defines :-
  627    '$cmd_option_val'(defines, Defs),
  628    apply_defines(Defs).
  629
  630apply_defines([]).
  631apply_defines([H|T]) :-
  632    apply_define(H),
  633    apply_defines(T).
  634
  635apply_define(Def) :-
  636    sub_atom(Def, B, _, A, '='),
  637    !,
  638    sub_atom(Def, 0, B, _, Flag),
  639    sub_atom(Def, _, A, 0, Value0),
  640    (   '$current_prolog_flag'(Flag, Value0, _Scope, Access, Type)
  641    ->  (   Access \== write
  642        ->  '$permission_error'(set, prolog_flag, Flag)
  643        ;   text_flag_value(Type, Value0, Value)
  644        ),
  645	set_prolog_flag(Flag, Value)
  646    ;   (   atom_number(Value0, Value)
  647	->  true
  648	;   Value = Value0
  649	),
  650	set_defined(Flag, Value)
  651    ).
  652apply_define(Def) :-
  653    atom_concat('no-', Flag, Def),
  654    !,
  655    set_user_boolean_flag(Flag, false).
  656apply_define(Def) :-
  657    set_user_boolean_flag(Def, true).
  658
  659set_user_boolean_flag(Flag, Value) :-
  660    current_prolog_flag(Flag, Old),
  661    !,
  662    (   Old == Value
  663    ->  true
  664    ;   set_prolog_flag(Flag, Value)
  665    ).
  666set_user_boolean_flag(Flag, Value) :-
  667    set_defined(Flag, Value).
  668
  669text_flag_value(integer, Text, Int) :-
  670    atom_number(Text, Int),
  671    !.
  672text_flag_value(float, Text, Float) :-
  673    atom_number(Text, Float),
  674    !.
  675text_flag_value(term, Text, Term) :-
  676    term_string(Term, Text, []),
  677    !.
  678text_flag_value(_, Value, Value).
  679
  680set_defined(Flag, Value) :-
  681    define_options(Flag, Options), !,
  682    create_prolog_flag(Flag, Value, Options).

 define_options(+Flag, -Options)

Define the options with which to create Flag. This can be used for known flags to control -for example- their type.

  689define_options('SDL_VIDEODRIVER', []).
  690define_options(_, [warn_not_accessed(true)]).

 init_optimise

Load library(apply_macros) if -O is effective.

  696init_optimise :-
  697    current_prolog_flag(optimise, true),
  698    !,
  699    use_module(user:library(apply_macros)).
  700init_optimise.
  701
  702opt_attach_packs :-
  703    current_prolog_flag(packs, true),
  704    !,
  705    attach_packs.
  706opt_attach_packs.
  707
  708set_toplevel :-
  709    '$cmd_option_val'(toplevel, TopLevelAtom),
  710    catch(term_to_atom(TopLevel, TopLevelAtom), E,
  711          (print_message(error, E),
  712           halt(1))),
  713    create_prolog_flag(toplevel_goal, TopLevel, [type(term)]).
  714
  715load_only :-
  716    current_prolog_flag(os_argv, OSArgv),
  717    memberchk('-l', OSArgv),
  718    current_prolog_flag(argv, Argv),
  719    \+ memberchk('-l', Argv).

 run_init_goals(+Goals) is det

Run registered initialization goals on order. If a goal fails, execution is halted.

  726run_init_goals([]).
  727run_init_goals([H|T]) :-
  728    run_init_goal(H),
  729    run_init_goals(T).
  730
  731run_init_goal(Text) :-
  732    catch(term_to_atom(Goal, Text), E,
  733          (   print_message(error, init_goal_syntax(E, Text)),
  734              halt(2)
  735          )),
  736    run_init_goal(Goal, Text).

 run_program_init is det

Run goals registered using

  742run_program_init :-
  743    forall('$init_goal'(when(program), Goal, Ctx),
  744           run_init_goal(Goal, @(Goal,Ctx))).
  745
  746run_main_init(_) :-
  747    findall(Goal-Ctx, '$init_goal'(when(main), Goal, Ctx), Pairs),
  748    '$last'(Pairs, Goal-Ctx),
  749    !,
  750    (   current_prolog_flag(toplevel_goal, default)
  751    ->  set_prolog_flag(toplevel_goal, halt)
  752    ;   true
  753    ),
  754    run_init_goal(Goal, @(Goal,Ctx)).
  755run_main_init(true) :-
  756    '$existence_error'(initialization, main).
  757run_main_init(_).
  758
  759run_init_goal(Goal, Ctx) :-
  760    (   catch_with_backtrace(user:Goal, E, true)
  761    ->  (   var(E)
  762        ->  true
  763        ;   init_goal_failed(E, Ctx)
  764        )
  765    ;   (   current_prolog_flag(verbose, silent)
  766        ->  Level = silent
  767        ;   Level = error
  768        ),
  769        print_message(Level, init_goal_failed(failed, Ctx)),
  770        halt(1)
  771    ).
  772
  773init_goal_failed(E, Ctx) :-
  774    print_message(error, init_goal_failed(E, Ctx)),
  775    init_goal_failed(E).
  776
  777init_goal_failed(_) :-
  778    thread_self(main),
  779    !,
  780    halt(2).
  781init_goal_failed(_).

 init_debug_flags is det

Initialize the various Prolog flags that control the debugger and toplevel.

  788init_debug_flags :-
  789    Keep = [keep(true)],
  790    create_prolog_flag(answer_write_options,
  791                       [ quoted(true), portray(true), max_depth(10),
  792                         spacing(next_argument)], Keep),
  793    create_prolog_flag(prompt_alternatives_on, determinism, Keep),
  794    create_prolog_flag(toplevel_extra_white_line, true, Keep),
  795    create_prolog_flag(toplevel_print_factorized, false, Keep),
  796    create_prolog_flag(print_write_options,
  797                       [ portray(true), quoted(true), numbervars(true) ],
  798                       Keep),
  799    create_prolog_flag(toplevel_residue_vars, false, Keep),
  800    create_prolog_flag(toplevel_list_wfs_residual_program, true, Keep),
  801    '$set_debugger_write_options'(print).

 setup_backtrace

Initialise printing a backtrace.

  807setup_backtrace :-
  808    (   \+ current_prolog_flag(backtrace, false),
  809        load_setup_file(library(prolog_stack))
  810    ->  true
  811    ;   true
  812    ).

 setup_colors is det

Setup interactive usage by enabling colored output.

  818setup_colors :-
  819    (   \+ current_prolog_flag(color_term, false),
  820        stream_property(user_input, tty(true)),
  821        stream_property(user_error, tty(true)),
  822        stream_property(user_output, tty(true)),
  823        \+ getenv('TERM', dumb),
  824        load_setup_file(user:library(ansi_term))
  825    ->  true
  826    ;   true
  827    ).

 setup_history

Enable per-directory persistent history.

  833setup_history :-
  834    (   \+ current_prolog_flag(save_history, false),
  835        stream_property(user_input, tty(true)),
  836        \+ current_prolog_flag(readline, false),
  837        load_setup_file(library(prolog_history))
  838    ->  prolog_history(enable)
  839    ;   true
  840    ).

 setup_readline

Setup line editing.

  846setup_readline :-
  847    (   stream_property(user_input, tty(true)),
  848        current_prolog_flag(tty_control, true),
  849        \+ getenv('TERM', dumb),
  850        (   current_prolog_flag(readline, ReadLine)
  851        ->  true
  852        ;   ReadLine = true
  853        ),
  854        readline_library(ReadLine, Library),
  855        (   load_setup_file(library(Library))
  856        ->  true
  857        ;   current_prolog_flag(epilog, true),
  858            print_message(warning,
  859                          error(existence_error(library, library(Library)),
  860                                _)),
  861            fail
  862        )
  863    ->  set_prolog_flag(readline, Library)
  864    ;   set_prolog_flag(readline, false)
  865    ).
  866
  867readline_library(true, Library) :-
  868    !,
  869    preferred_readline(Library).
  870readline_library(false, _) :-
  871    !,
  872    fail.
  873readline_library(Library, Library).
  874
  875preferred_readline(editline).

 load_setup_file(+File) is semidet

Load a file and fail silently if the file does not exist.

  881load_setup_file(File) :-
  882    catch(load_files(File,
  883                     [ silent(true),
  884                       if(not_loaded)
  885                     ]), error(_,_), fail).

 setup_app is det

When running as an "app", behave as such. The behaviour depends on the platform.

Windows

If Prolog is started using --win_app, try to change directory to <My Documents>\Prolog.

  897:- if(current_prolog_flag(windows,true)).  898
  899setup_app :-
  900    current_prolog_flag(associated_file, _),
  901    !.
  902setup_app :-
  903    '$cmd_option_val'(win_app, true),
  904    !,
  905    catch(my_prolog, E, print_message(warning, E)).
  906setup_app.
  907
  908my_prolog :-
  909    win_folder(personal, MyDocs),
  910    atom_concat(MyDocs, '/Prolog', PrologDir),
  911    (   ensure_dir(PrologDir)
  912    ->  working_directory(_, PrologDir)
  913    ;   working_directory(_, MyDocs)
  914    ).
  915
  916ensure_dir(Dir) :-
  917    exists_directory(Dir),
  918    !.
  919ensure_dir(Dir) :-
  920    catch(make_directory(Dir), E, (print_message(warning, E), fail)).
  921
  922:- elif(current_prolog_flag(apple, true)).  923use_app_settings(true).                        % Indicate we need app settings
  924
  925setup_app :-
  926    apple_set_locale,
  927    current_prolog_flag(associated_file, _),
  928    !.
  929setup_app :-
  930    current_prolog_flag(bundle, true),
  931    current_prolog_flag(epilog, true),
  932    getenv('__CFBundleIdentifier', _),
  933    !,
  934    setup_macos_app.
  935setup_app.
  936
  937apple_set_locale :-
  938    (   getenv('LC_CTYPE', 'UTF-8'),
  939        apple_current_locale_identifier(LocaleID),
  940        atom_concat(LocaleID, '.UTF-8', Locale),
  941        catch(setlocale(ctype, _Old, Locale), _, fail)
  942    ->  setenv('LANG', Locale),
  943        unsetenv('LC_CTYPE')
  944    ;   true
  945    ).
  946
  947setup_macos_app :-
  948    restore_working_directory,
  949    !.
  950setup_macos_app :-
  951    expand_file_name('~/Prolog', [PrologDir]),
  952    (   exists_directory(PrologDir)
  953    ->  true
  954    ;   catch(make_directory(PrologDir), MkDirError,
  955              print_message(warning, MkDirError))
  956    ),
  957    catch(working_directory(_, PrologDir), CdError,
  958          print_message(warning, CdError)),
  959    !.
  960setup_macos_app.
  961
  962:- elif(current_prolog_flag(emscripten, true)).  963setup_app.
  964:- else.  965use_app_settings(true).                        % Indicate we need app settings
  966
  967% Other (Unix-like) platforms.
  968setup_app :-
  969    running_as_app,
  970    restore_working_directory,
  971    !.
  972setup_app.

 running_as_app is semidet

True if we were started from the dock.

  978running_as_app :-
  979%   getenv('FLATPAK_SANDBOX_DIR', _),
  980    current_prolog_flag(epilog, true),
  981    stream_property(In, file_no(0)),
  982    \+ stream_property(In, tty(true)),
  983    !.
  984
  985:- endif.  986
  987
  988:- if((current_predicate(use_app_settings/1),
  989       use_app_settings(true))).  990
  991
  992                /*******************************
  993                *    APP WORKING DIRECTORY     *
  994                *******************************/
  995
  996save_working_directory :-
  997    working_directory(WD, WD),
  998    app_settings(Settings),
  999    (   Settings.get(working_directory) == WD
 1000    ->  true
 1001    ;   app_save_settings(Settings.put(working_directory, WD))
 1002    ).
 1003
 1004restore_working_directory :-
 1005    at_halt(save_working_directory),
 1006    app_settings(Settings),
 1007    WD = Settings.get(working_directory),
 1008    catch(working_directory(_, WD), _, fail),
 1009    !.
 1010
 1011                /*******************************
 1012                *           SETTINGS           *
 1013                *******************************/

 app_settings(-Settings:dict) is det

Get a dict holding the persistent application settings.

 1019app_settings(Settings) :-
 1020    app_settings_file(File),
 1021    access_file(File, read),
 1022    catch(setup_call_cleanup(
 1023              open(File, read, In, [encoding(utf8)]),
 1024              read_term(In, Settings, []),
 1025              close(In)),
 1026          Error,
 1027          (print_message(warning, Error), fail)),
 1028    !.
 1029app_settings(#{}).

 app_save_settings(+Settings:dict) is det

Save the given application settings dict.

 1035app_save_settings(Settings) :-
 1036    app_settings_file(File),
 1037    catch(setup_call_cleanup(
 1038              open(File, write, Out, [encoding(utf8)]),
 1039              write_term(Out, Settings,
 1040                         [ quoted(true),
 1041                           module(system), % default operators
 1042                           fullstop(true),
 1043                           nl(true)
 1044                         ]),
 1045              close(Out)),
 1046          Error,
 1047          (print_message(warning, Error), fail)).
 1048
 1049
 1050app_settings_file(File) :-
 1051    absolute_file_name(user_app_config('app_settings.pl'), File,
 1052                       [ access(write),
 1053                         file_errors(fail)
 1054                       ]).
 1055:- endif.% app_settings
 1056
 1057                /*******************************
 1058                *           TOPLEVEL           *
 1059                *******************************/
 1060
 1061:- '$hide'('$toplevel'/0).              % avoid in the GUI stacktrace

 $toplevel

Called from PL_toplevel()

 1067'$toplevel' :-
 1068    '$runtoplevel',
 1069    print_message(informational, halt).

 $runtoplevel

Actually run the toplevel. The values default and prolog both start the interactive toplevel, where prolog implies the user gave -t prolog.

See also

- prolog/0 is the default interactive toplevel

 1079'$runtoplevel' :-
 1080    current_prolog_flag(toplevel_goal, TopLevel0),
 1081    toplevel_goal(TopLevel0, TopLevel),
 1082    user:TopLevel.
 1083
 1084:- dynamic  setup_done/0. 1085:- volatile setup_done/0. 1086
 1087toplevel_goal(default, '$query_loop') :-
 1088    !,
 1089    setup_interactive.
 1090toplevel_goal(prolog, '$query_loop') :-
 1091    !,
 1092    setup_interactive.
 1093toplevel_goal(Goal, Goal).
 1094
 1095setup_interactive :-
 1096    setup_done,
 1097    !.
 1098setup_interactive :-
 1099    asserta(setup_done),
 1100    catch(setup_backtrace, E, print_message(warning, E)),
 1101    catch(setup_readline,  E, print_message(warning, E)),
 1102    catch(setup_history,   E, print_message(warning, E)).

 $compile

Toplevel called when invoked with -c option.

 1108'$compile' :-
 1109    (   catch('$compile_', E, (print_message(error, E), halt(1)))
 1110    ->  true
 1111    ;   print_message(error, error(goal_failed('$compile'), _)),
 1112        halt(1)
 1113    ),
 1114    halt.                               % set exit code
 1115
 1116'$compile_' :-
 1117    '$load_system_init_file',
 1118    catch(setup_colors, _, true),
 1119    '$set_file_search_paths',
 1120    init_debug_flags,
 1121    '$run_initialization',
 1122    opt_attach_packs,
 1123    use_module(library(qsave)),
 1124    qsave:qsave_toplevel.

 $config

Toplevel when invoked with --dump-runtime-variables

 1130'$config' :-
 1131    '$load_system_init_file',
 1132    '$set_file_search_paths',
 1133    init_debug_flags,
 1134    '$run_initialization',
 1135    load_files(library(prolog_config)),
 1136    (   catch(prolog_dump_runtime_variables, E,
 1137              (print_message(error, E), halt(1)))
 1138    ->  true
 1139    ;   print_message(error, error(goal_failed(prolog_dump_runtime_variables),_))
 1140    ).
 1141
 1142
 1143                /********************************
 1144                *    USER INTERACTIVE LOOP      *
 1145                *********************************/

 prolog:repl_loop_hook(+BeginEnd, +BreakLevel) is nondet

Multifile hook that allows acting on starting/stopping the interactive REPL loop. Called as

forall(prolog:repl_loop_hook(BeginEnd, BreakLevel), true)

Arguments:

BeginEnd	- is one of begin or end
BreakLevel	- is 0 for the normal toplevel, -1 when non-interactive and >0 for break environments.

 1158:- multifile
 1159    prolog:repl_loop_hook/2.

 prolog

Run the Prolog toplevel. This is now the same as break/0, which pretends to be in a break-level if there is a parent environment.

 1167prolog :-
 1168    break.
 1169
 1170:- create_prolog_flag(toplevel_mode, backtracking, []).

 $query_loop

Run the normal Prolog query loop. Note that the query is not protected by catch/3. Dealing with unhandled exceptions is done by the C-function query_loop(). This ensures that unhandled exceptions are really unhandled (in Prolog).

 1179'$query_loop' :-
 1180    break_level(BreakLev),
 1181    setup_call_cleanup(
 1182        notrace(call_repl_loop_hook(begin, BreakLev, IsToplevel)),
 1183        '$query_loop'(BreakLev),
 1184        notrace(call_repl_loop_hook(end, BreakLev, IsToplevel))).
 1185
 1186call_repl_loop_hook(begin, BreakLev, IsToplevel) =>
 1187    (   current_prolog_flag(toplevel_thread, IsToplevel)
 1188    ->  true
 1189    ;   IsToplevel = false
 1190    ),
 1191    set_prolog_flag(toplevel_thread, true),
 1192    call_repl_loop_hook_(begin, BreakLev).
 1193call_repl_loop_hook(end, BreakLev, IsToplevel) =>
 1194    set_prolog_flag(toplevel_thread, IsToplevel),
 1195    call_repl_loop_hook_(end, BreakLev).
 1196
 1197call_repl_loop_hook_(BeginEnd, BreakLev) :-
 1198    forall(prolog:repl_loop_hook(BeginEnd, BreakLev), true).
 1199
 1200
 1201'$query_loop'(BreakLev) :-
 1202    current_prolog_flag(toplevel_mode, recursive),
 1203    !,
 1204    read_expanded_query(BreakLev, Query, Bindings),
 1205    (   Query == end_of_file
 1206    ->  print_message(query, query(eof))
 1207    ;   '$call_no_catch'('$execute_query'(Query, Bindings, _)),
 1208        (   current_prolog_flag(toplevel_mode, recursive)
 1209        ->  '$query_loop'(BreakLev)
 1210        ;   '$switch_toplevel_mode'(backtracking),
 1211            '$query_loop'(BreakLev)     % Maybe throw('$switch_toplevel_mode')?
 1212        )
 1213    ).
 1214'$query_loop'(BreakLev) :-
 1215    repeat,
 1216        read_expanded_query(BreakLev, Query, Bindings),
 1217        (   Query == end_of_file
 1218        ->  !, print_message(query, query(eof))
 1219        ;   '$execute_query'(Query, Bindings, _),
 1220            (   current_prolog_flag(toplevel_mode, recursive)
 1221            ->  !,
 1222                '$switch_toplevel_mode'(recursive),
 1223                '$query_loop'(BreakLev)
 1224            ;   fail
 1225            )
 1226        ).
 1227
 1228break_level(BreakLev) :-
 1229    (   current_prolog_flag(break_level, BreakLev)
 1230    ->  true
 1231    ;   BreakLev = -1
 1232    ).
 1233
 1234read_expanded_query(BreakLev, ExpandedQuery, ExpandedBindings) :-
 1235    '$current_typein_module'(TypeIn),
 1236    (   stream_property(user_input, tty(true))
 1237    ->  '$system_prompt'(TypeIn, BreakLev, Prompt),
 1238        prompt(Old, '|    ')
 1239    ;   Prompt = '',
 1240        prompt(Old, '')
 1241    ),
 1242    trim_stacks,
 1243    trim_heap,
 1244    repeat,
 1245      (   catch(read_query(Prompt, Query, Bindings),
 1246                error(io_error(_,_),_), fail)
 1247      ->  prompt(_, Old),
 1248          catch(call_expand_query(Query, ExpandedQuery,
 1249                                  Bindings, ExpandedBindings),
 1250                Error,
 1251                (print_message(error, Error), fail))
 1252      ;   set_prolog_flag(debug_on_error, false),
 1253          thread_exit(io_error)
 1254      ),
 1255    !.

 read_query(+Prompt, -Goal, -Bindings) is det

Read the next query. The first clause deals with the case where !-based history is enabled. The second is used if we have command line editing.

 1264:- multifile
 1265    prolog:history/2. 1266
 1267:- if(current_prolog_flag(emscripten, true)). 1268read_query(_Prompt, Goal, Bindings) :-
 1269    '$can_yield',
 1270    !,
 1271    await(query, GoalString),
 1272    term_string(Goal, GoalString, [variable_names(Bindings)]).
 1273:- endif. 1274read_query(Prompt, Goal, Bindings) :-
 1275    prolog:history(current_input, enabled),
 1276    !,
 1277    read_term_with_history(
 1278        Goal,
 1279        [ show(h),
 1280          help('!h'),
 1281          no_save([trace]),
 1282          prompt(Prompt),
 1283          variable_names(Bindings)
 1284        ]).
 1285read_query(Prompt, Goal, Bindings) :-
 1286    remove_history_prompt(Prompt, Prompt1),
 1287    repeat,                                 % over syntax errors
 1288    prompt1(Prompt1),
 1289    read_query_line(user_input, Line),
 1290    '$current_typein_module'(TypeIn),
 1291    catch(read_term_from_atom(Line, Goal,
 1292                              [ variable_names(Bindings),
 1293                                module(TypeIn),
 1294                                blob(resolve)
 1295                              ]), E,
 1296          (   print_message(error, E),
 1297              fail
 1298          )),
 1299    !.

 read_query_line(+Input, -Query:atom) is det

Read a query as an atom. If Query is '$silent'(Goal), execute Goal in module user and read the next query. This supports injecting goals in some GNU-Emacs modes.

 1307read_query_line(Input, Line) :-
 1308    stream_property(Input, error(true)),
 1309    !,
 1310    Line = end_of_file.
 1311read_query_line(Input, Line) :-
 1312    catch(read_term_as_atom(Input, Line0), Error, true),
 1313    save_debug_after_read,
 1314    (   var(Error)
 1315    ->  (   catch(term_string(Goal, Line0), error(_,_), fail),
 1316            Goal = '$silent'(SilentGoal)
 1317        ->  Error = error(_,_),
 1318            catch_with_backtrace(ignore(SilentGoal), Error,
 1319                                 print_message(error, Error)),
 1320            read_query_line(Input, Line)
 1321        ;   Line = Line0
 1322        )
 1323    ;   catch(print_message(error, Error), _, true),
 1324        (   Error = error(syntax_error(_),_)
 1325        ->  fail
 1326        ;   throw(Error)
 1327        )
 1328    ).

 read_term_as_atom(+Input, -Line)

Read the next term as an atom and skip to the newline or a non-space character.

 1335read_term_as_atom(In, Line) :-
 1336    '$raw_read'(In, Line),
 1337    (   Line == end_of_file
 1338    ->  true
 1339    ;   skip_to_nl(In)
 1340    ).

 skip_to_nl(+Input) is det

Read input after the term. Skips white space and %... comment until the end of the line or a non-blank character.

 1347skip_to_nl(In) :-
 1348    repeat,
 1349    peek_char(In, C),
 1350    (   C == '%'
 1351    ->  skip(In, '\n')
 1352    ;   char_type(C, space)
 1353    ->  get_char(In, _),
 1354        C == '\n'
 1355    ;   true
 1356    ),
 1357    !.
 1358
 1359remove_history_prompt('', '') :- !.
 1360remove_history_prompt(Prompt0, Prompt) :-
 1361    atom_chars(Prompt0, Chars0),
 1362    clean_history_prompt_chars(Chars0, Chars1),
 1363    delete_leading_blanks(Chars1, Chars),
 1364    atom_chars(Prompt, Chars).
 1365
 1366clean_history_prompt_chars([], []).
 1367clean_history_prompt_chars(['~', !|T], T) :- !.
 1368clean_history_prompt_chars([H|T0], [H|T]) :-
 1369    clean_history_prompt_chars(T0, T).
 1370
 1371delete_leading_blanks([' '|T0], T) :-
 1372    !,
 1373    delete_leading_blanks(T0, T).
 1374delete_leading_blanks(L, L).
 1375
 1376
 1377                 /*******************************
 1378                 *        TOPLEVEL DEBUG        *
 1379                 *******************************/

 save_debug_after_read

Called right after the toplevel read to save the debug status if it was modified from the GUI thread using e.g.

thread_signal(main, gdebug)

bug

- Ideally, the prompt would change if debug mode is enabled. That is hard to realise with all the different console interfaces supported by SWI-Prolog.

 1394save_debug_after_read :-
 1395    current_prolog_flag(debug, true),
 1396    !,
 1397    save_debug.
 1398save_debug_after_read.
 1399
 1400save_debug :-
 1401    (   tracing,
 1402        notrace
 1403    ->  Tracing = true
 1404    ;   Tracing = false
 1405    ),
 1406    current_prolog_flag(debug, Debugging),
 1407    set_prolog_flag(debug, false),
 1408    create_prolog_flag(query_debug_settings,
 1409                       debug(Debugging, Tracing), []).
 1410
 1411restore_debug :-
 1412    current_prolog_flag(query_debug_settings, debug(Debugging, Tracing)),
 1413    set_prolog_flag(debug, Debugging),
 1414    (   Tracing == true
 1415    ->  trace
 1416    ;   true
 1417    ).
 1418
 1419:- initialization
 1420    create_prolog_flag(query_debug_settings, debug(false, false), []). 1421
 1422
 1423                /********************************
 1424                *            PROMPTING          *
 1425                ********************************/
 1426
 1427'$system_prompt'(Module, BrekLev, Prompt) :-
 1428    current_prolog_flag(toplevel_prompt, PAtom),
 1429    atom_codes(PAtom, P0),
 1430    (    Module \== user
 1431    ->   '$substitute'('~m', [Module, ': '], P0, P1)
 1432    ;    '$substitute'('~m', [], P0, P1)
 1433    ),
 1434    (    BrekLev > 0
 1435    ->   '$substitute'('~l', ['[', BrekLev, '] '], P1, P2)
 1436    ;    '$substitute'('~l', [], P1, P2)
 1437    ),
 1438    current_prolog_flag(query_debug_settings, debug(Debugging, Tracing)),
 1439    (    Tracing == true
 1440    ->   '$substitute'('~d', ['[trace] '], P2, P3)
 1441    ;    Debugging == true
 1442    ->   '$substitute'('~d', ['[debug] '], P2, P3)
 1443    ;    '$substitute'('~d', [], P2, P3)
 1444    ),
 1445    atom_chars(Prompt, P3).
 1446
 1447'$substitute'(From, T, Old, New) :-
 1448    atom_codes(From, FromCodes),
 1449    phrase(subst_chars(T), T0),
 1450    '$append'(Pre, S0, Old),
 1451    '$append'(FromCodes, Post, S0) ->
 1452    '$append'(Pre, T0, S1),
 1453    '$append'(S1, Post, New),
 1454    !.
 1455'$substitute'(_, _, Old, Old).
 1456
 1457subst_chars([]) -->
 1458    [].
 1459subst_chars([H|T]) -->
 1460    { atomic(H),
 1461      !,
 1462      atom_codes(H, Codes)
 1463    },
 1464    Codes,
 1465    subst_chars(T).
 1466subst_chars([H|T]) -->
 1467    H,
 1468    subst_chars(T).
 1469
 1470
 1471                /********************************
 1472                *           EXECUTION           *
 1473                ********************************/

 $execute_query(Goal, Bindings, -Truth) is det

Execute Goal using Bindings.

 1479'$execute_query'(Var, _, true) :-
 1480    var(Var),
 1481    !,
 1482    print_message(informational, var_query(Var)).
 1483'$execute_query'(Goal, Bindings, Truth) :-
 1484    '$current_typein_module'(TypeIn),
 1485    '$dwim_correct_goal'(TypeIn:Goal, Bindings, Corrected),
 1486    !,
 1487    setup_call_cleanup(
 1488        '$set_source_module'(M0, TypeIn),
 1489        expand_goal(Corrected, Expanded),
 1490        '$set_source_module'(M0)),
 1491    print_message(silent, toplevel_goal(Expanded, Bindings)),
 1492    '$execute_goal2'(Expanded, Bindings, Truth).
 1493'$execute_query'(_, _, false) :-
 1494    notrace,
 1495    print_message(query, query(no)).
 1496
 1497'$execute_goal2'(Goal, Bindings, true) :-
 1498    restore_debug,
 1499    '$current_typein_module'(TypeIn),
 1500    residue_vars(TypeIn:Goal, Vars, TypeIn:Delays, Chp),
 1501    deterministic(Det),
 1502    (   save_debug
 1503    ;   restore_debug, fail
 1504    ),
 1505    flush_output(user_output),
 1506    (   Det == true
 1507    ->  DetOrChp = true
 1508    ;   DetOrChp = Chp
 1509    ),
 1510    call_expand_answer(Goal, Bindings, NewBindings),
 1511    (    \+ \+ write_bindings(NewBindings, Vars, Delays, DetOrChp)
 1512    ->   !
 1513    ).
 1514'$execute_goal2'(_, _, false) :-
 1515    save_debug,
 1516    print_message(query, query(no)).
 1517
 1518residue_vars(Goal, Vars, Delays, Chp) :-
 1519    current_prolog_flag(toplevel_residue_vars, true),
 1520    !,
 1521    '$wfs_call'(call_residue_vars(stop_backtrace(Goal, Chp), Vars), Delays).
 1522residue_vars(Goal, [], Delays, Chp) :-
 1523    '$wfs_call'(stop_backtrace(Goal, Chp), Delays).
 1524
 1525stop_backtrace(Goal, Chp) :-
 1526    toplevel_call(Goal),
 1527    prolog_current_choice(Chp).
 1528
 1529toplevel_call(Goal) :-
 1530    call(Goal),
 1531    no_lco.
 1532
 1533no_lco.

 write_bindings(+Bindings, +ResidueVars, +Delays, +DetOrChp) is semidet

Write bindings resulting from a query. The flag prompt_alternatives_on determines whether the user is prompted for alternatives. groundness gives the classical behaviour, determinism is considered more adequate and informative.

Succeeds if the user accepts the answer and fails otherwise.

Arguments:

ResidueVars

- are the residual constraints and provided if the prolog flag toplevel_residue_vars is set to project.

 1549write_bindings(Bindings, ResidueVars, Delays, DetOrChp) :-
 1550    '$current_typein_module'(TypeIn),
 1551    translate_bindings(Bindings, Bindings1, ResidueVars, TypeIn:Residuals),
 1552    omit_qualifier(Delays, TypeIn, Delays1),
 1553    write_bindings2(Bindings, Bindings1, Residuals, Delays1, DetOrChp).
 1554
 1555write_bindings2(OrgBindings, [], Residuals, Delays, _) :-
 1556    current_prolog_flag(prompt_alternatives_on, groundness),
 1557    !,
 1558    name_vars(OrgBindings, [], t(Residuals, Delays)),
 1559    print_message(query, query(yes(Delays, Residuals))).
 1560write_bindings2(OrgBindings, Bindings, Residuals, Delays, true) :-
 1561    current_prolog_flag(prompt_alternatives_on, determinism),
 1562    !,
 1563    name_vars(OrgBindings, Bindings, t(Residuals, Delays)),
 1564    print_message(query, query(yes(Bindings, Delays, Residuals))).
 1565write_bindings2(OrgBindings, Bindings, Residuals, Delays, Chp) :-
 1566    repeat,
 1567        name_vars(OrgBindings, Bindings, t(Residuals, Delays)),
 1568        print_message(query, query(more(Bindings, Delays, Residuals))),
 1569        get_respons(Action, Chp),
 1570    (   Action == redo
 1571    ->  !, fail
 1572    ;   Action == show_again
 1573    ->  fail
 1574    ;   !,
 1575        print_message(query, query(done))
 1576    ).

 name_vars(+OrgBinding, +Bindings, +Term) is det

Give a name _[A-Z][0-9]* to all variables in Term, that do not have a name due to Bindings. Singleton variables in Term are named _. The behavior depends on these Prolog flags:

toplevel_name_variables

Only act when true, else name_vars/3 is a no-op.

toplevel_print_anon

Variables are named by unifying them to '$VAR'(Name)

Arguments:

Bindings

- is a list Name=Value

 1592name_vars(OrgBindings, Bindings, Term) :-
 1593    current_prolog_flag(toplevel_name_variables, true),
 1594    answer_flags_imply_numbervars,
 1595    !,
 1596    '$term_multitons'(t(Bindings,Term), Vars),
 1597    bindings_var_names(OrgBindings, Bindings, VarNames),
 1598    name_vars_(Vars, VarNames, 0),
 1599    term_variables(t(Bindings,Term), SVars),
 1600    anon_vars(SVars).
 1601name_vars(_OrgBindings, _Bindings, _Term).
 1602
 1603name_vars_([], _, _).
 1604name_vars_([H|T], Bindings, N) :-
 1605    name_var(Bindings, Name, N, N1),
 1606    H = '$VAR'(Name),
 1607    name_vars_(T, Bindings, N1).
 1608
 1609anon_vars([]).
 1610anon_vars(['$VAR'('_')|T]) :-
 1611    anon_vars(T).

 name_var(+Reserved, -Name, +N0, -N) is det

True when Name is a valid name for a new variable where the search is guided by the number N0. Name may not appear in Reserved.

 1618name_var(Reserved, Name, N0, N) :-
 1619    between(N0, infinite, N1),
 1620    I is N1//26,
 1621    J is 0'A + N1 mod 26,
 1622    (   I == 0
 1623    ->  format(atom(Name), '_~c', [J])
 1624    ;   format(atom(Name), '_~c~d', [J, I])
 1625    ),
 1626    \+ memberchk(Name, Reserved),
 1627    !,
 1628    N is N1+1.

 bindings_var_names(+OrgBindings, +TransBindings, -VarNames) is det

Find the joined set of variable names in the original bindings and translated bindings. When generating new names, we better also omit names that appear in the original bindings (but not in the translated bindigns).

 1637bindings_var_names(OrgBindings, TransBindings, VarNames) :-
 1638    phrase(bindings_var_names_(OrgBindings), VarNames0, Tail),
 1639    phrase(bindings_var_names_(TransBindings), Tail, []),
 1640    sort(VarNames0, VarNames).

 bindings_var_names_(+Bindings)// is det

Produce a list of variable names that appear in Bindings. This deals both with the single and joined representation of bindings.

 1647bindings_var_names_([]) --> [].
 1648bindings_var_names_([H|T]) -->
 1649    binding_var_names(H),
 1650    bindings_var_names_(T).
 1651
 1652binding_var_names(binding(Vars,_Value,_Subst)) ==>
 1653    var_names(Vars).
 1654binding_var_names(Name=_Value) ==>
 1655    [Name].
 1656
 1657var_names([]) --> [].
 1658var_names([H|T]) --> [H], var_names(T).

 answer_flags_imply_numbervars

True when the answer will be written recognising '$VAR'(N). If this is not the case we should not try to name the variables.

 1666answer_flags_imply_numbervars :-
 1667    current_prolog_flag(answer_write_options, Options),
 1668    numbervars_option(Opt),
 1669    '$option'(Opt, Options),
 1670    !.
 1671
 1672numbervars_option(portray(true)).
 1673numbervars_option(portrayed(true)).
 1674numbervars_option(numbervars(true)).

 residual_goals(:NonTerminal)

Directive that registers NonTerminal as a collector for residual goals.

 1681:- multifile
 1682    residual_goal_collector/1. 1683
 1684:- meta_predicate
 1685    residual_goals(2). 1686
 1687residual_goals(NonTerminal) :-
 1688    throw(error(context_error(nodirective, residual_goals(NonTerminal)), _)).
 1689
 1690system:term_expansion((:- residual_goals(NonTerminal)),
 1691                      '$toplevel':residual_goal_collector(M2:Head)) :-
 1692    \+ current_prolog_flag(xref, true),
 1693    prolog_load_context(module, M),
 1694    strip_module(M:NonTerminal, M2, Head),
 1695    '$must_be'(callable, Head).

 prolog:residual_goals// is det

DCG that collects residual goals that are not associated with the answer through attributed variables.

 1702:- public prolog:residual_goals//0. 1703
 1704prolog:residual_goals -->
 1705    { findall(NT, residual_goal_collector(NT), NTL) },
 1706    collect_residual_goals(NTL).
 1707
 1708collect_residual_goals([]) --> [].
 1709collect_residual_goals([H|T]) -->
 1710    ( call(H) -> [] ; [] ),
 1711    collect_residual_goals(T).

 prolog:translate_bindings(+Bindings0, -Bindings, +ResidueVars, +ResidualGoals, -Residuals) is det

Translate the raw variable bindings resulting from successfully completing a query into a binding list and list of residual goals suitable for human consumption.

Arguments:

Bindings

- is a list of binding(Vars,Value,Substitutions), where Vars is a list of variable names. E.g. binding(['A','B'],42,[])` means that both the variable A and B have the value 42. Values may contain terms '$VAR'(Name) to indicate sharing with a given variable. Value is always an acyclic term. If cycles appear in the answer, Substitutions contains a list of substitutions that restore the original term.

Residuals

- is a pair of two lists representing residual goals. The first element of the pair are residuals related to the query variables and the second are related that are disconnected from the query.

 1736:- public
 1737    prolog:translate_bindings/5. 1738:- meta_predicate
 1739    prolog:translate_bindings(+, -, +, +, :). 1740
 1741prolog:translate_bindings(Bindings0, Bindings, ResVars, ResGoals, Residuals) :-
 1742    translate_bindings(Bindings0, Bindings, ResVars, ResGoals, Residuals),
 1743    name_vars(Bindings0, Bindings, t(ResVars, ResGoals, Residuals)).
 1744
 1745% should not be required.
 1746prolog:name_vars(Bindings, Term) :- name_vars([], Bindings, Term).
 1747prolog:name_vars(Bindings0, Bindings, Term) :- name_vars(Bindings0, Bindings, Term).
 1748
 1749translate_bindings(Bindings0, Bindings, ResidueVars, Residuals) :-
 1750    prolog:residual_goals(ResidueGoals, []),
 1751    translate_bindings(Bindings0, Bindings, ResidueVars, ResidueGoals,
 1752                       Residuals).
 1753
 1754translate_bindings(Bindings0, Bindings, [], [], _:[]-[]) :-
 1755    term_attvars(Bindings0, []),
 1756    !,
 1757    join_same_bindings(Bindings0, Bindings1),
 1758    factorize_bindings(Bindings1, Bindings2),
 1759    bind_vars(Bindings2, Bindings3),
 1760    filter_bindings(Bindings3, Bindings).
 1761translate_bindings(Bindings0, Bindings, ResidueVars, ResGoals0,
 1762                   TypeIn:Residuals-HiddenResiduals) :-
 1763    project_constraints(Bindings0, ResidueVars),
 1764    hidden_residuals(ResidueVars, Bindings0, HiddenResiduals0),
 1765    omit_qualifiers(HiddenResiduals0, TypeIn, HiddenResiduals),
 1766    copy_term(Bindings0+ResGoals0, Bindings1+ResGoals1, Residuals0),
 1767    '$append'(ResGoals1, Residuals0, Residuals1),
 1768    omit_qualifiers(Residuals1, TypeIn, Residuals),
 1769    join_same_bindings(Bindings1, Bindings2),
 1770    factorize_bindings(Bindings2, Bindings3),
 1771    bind_vars(Bindings3, Bindings4),
 1772    filter_bindings(Bindings4, Bindings).
 1773
 1774hidden_residuals(ResidueVars, Bindings, Goal) :-
 1775    term_attvars(ResidueVars, Remaining),
 1776    term_attvars(Bindings, QueryVars),
 1777    subtract_vars(Remaining, QueryVars, HiddenVars),
 1778    copy_term(HiddenVars, _, Goal).
 1779
 1780subtract_vars(All, Subtract, Remaining) :-
 1781    sort(All, AllSorted),
 1782    sort(Subtract, SubtractSorted),
 1783    ord_subtract(AllSorted, SubtractSorted, Remaining).
 1784
 1785ord_subtract([], _Not, []).
 1786ord_subtract([H1|T1], L2, Diff) :-
 1787    diff21(L2, H1, T1, Diff).
 1788
 1789diff21([], H1, T1, [H1|T1]).
 1790diff21([H2|T2], H1, T1, Diff) :-
 1791    compare(Order, H1, H2),
 1792    diff3(Order, H1, T1, H2, T2, Diff).
 1793
 1794diff12([], _H2, _T2, []).
 1795diff12([H1|T1], H2, T2, Diff) :-
 1796    compare(Order, H1, H2),
 1797    diff3(Order, H1, T1, H2, T2, Diff).
 1798
 1799diff3(<,  H1, T1,  H2, T2, [H1|Diff]) :-
 1800    diff12(T1, H2, T2, Diff).
 1801diff3(=, _H1, T1, _H2, T2, Diff) :-
 1802    ord_subtract(T1, T2, Diff).
 1803diff3(>,  H1, T1, _H2, T2, Diff) :-
 1804    diff21(T2, H1, T1, Diff).

 project_constraints(+Bindings, +ResidueVars) is det

Call <module>:project_attributes/2 if the Prolog flag toplevel_residue_vars is set to project.

 1812project_constraints(Bindings, ResidueVars) :-
 1813    !,
 1814    term_attvars(Bindings, AttVars),
 1815    phrase(attribute_modules(AttVars), Modules0),
 1816    sort(Modules0, Modules),
 1817    term_variables(Bindings, QueryVars),
 1818    project_attributes(Modules, QueryVars, ResidueVars).
 1819project_constraints(_, _).
 1820
 1821project_attributes([], _, _).
 1822project_attributes([M|T], QueryVars, ResidueVars) :-
 1823    (   current_predicate(M:project_attributes/2),
 1824        catch(M:project_attributes(QueryVars, ResidueVars), E,
 1825              print_message(error, E))
 1826    ->  true
 1827    ;   true
 1828    ),
 1829    project_attributes(T, QueryVars, ResidueVars).
 1830
 1831attribute_modules([]) --> [].
 1832attribute_modules([H|T]) -->
 1833    { get_attrs(H, Attrs) },
 1834    attrs_modules(Attrs),
 1835    attribute_modules(T).
 1836
 1837attrs_modules([]) --> [].
 1838attrs_modules(att(Module, _, More)) -->
 1839    [Module],
 1840    attrs_modules(More).

 join_same_bindings(Bindings0, Bindings)

Join variables that are bound to the same value. Note that we return the last value. This is because the factorization may be different and ultimately the names will be printed as V1 = V2, ... VN = Value. Using the last, Value has the factorization of VN.