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    1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  1997-2021, 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:- module('$messages',
   39          [ print_message/2,            % +Kind, +Term
   40            print_message_lines/3,      % +Stream, +Prefix, +Lines
   41            message_to_string/2         % +Term, -String
   42          ]).   43
   44:- multifile
   45    prolog:message//1,              % entire message
   46    prolog:error_message//1,        % 1-st argument of error term
   47    prolog:message_context//1,      % Context of error messages
   48    prolog:deprecated//1,	    % Deprecated features
   49    prolog:message_location//1,     % (File) location of error messages
   50    prolog:message_line_element/2.  % Extend printing
   51:- '$hide'((
   52    prolog:message//1,
   53    prolog:error_message//1,
   54    prolog:message_context//1,
   55    prolog:deprecated//1,
   56    prolog:message_location//1,
   57    prolog:message_line_element/2)).   58% Lang, Term versions
   59:- multifile
   60    prolog:message//2,              % entire message
   61    prolog:error_message//2,        % 1-st argument of error term
   62    prolog:message_context//2,      % Context of error messages
   63    prolog:message_location//2,	    % (File) location of error messages
   64    prolog:deprecated//2.	    % Deprecated features
   65:- '$hide'((
   66    prolog:message//2,
   67    prolog:error_message//2,
   68    prolog:message_context//2,
   69    prolog:deprecated//2,
   70    prolog:message_location//2)).   71
   72:- discontiguous
   73    prolog_message/3.   74
   75:- public
   76    translate_message//1,           % +Message (deprecated)
   77    prolog:translate_message//1.    % +Message
   78
   79:- create_prolog_flag(message_context, [thread], []).
 translate_message(+Term)// is det
Translate a message Term into message lines. The produced lines is a list of
nl
Emit a newline
Fmt - Args
Emit the result of format(Fmt, Args)
Fmt
Emit the result of format(Fmt)
ansi(Code, Fmt, Args)
Use ansi_format/3 for color output.
flush
Used only as last element of the list. Simply flush the output instead of producing a final newline.
at_same_line
Start the messages at the same line (instead of using ~N)
deprecated
- Use code for message translation should call translate_message//1.
  103prolog:translate_message(Term) -->
  104    translate_message(Term).
 translate_message(+Term)// is det
Translate a message term into message lines. This version may be called from user and library definitions for message translation.
  111translate_message(Term) -->
  112    { nonvar(Term) },
  113    (   { message_lang(Lang) },
  114        prolog:message(Lang, Term)
  115    ;   prolog:message(Term)
  116    ),
  117    !.
  118translate_message(Term) -->
  119    { nonvar(Term) },
  120    translate_message2(Term),
  121    !.
  122translate_message(Term) -->
  123    { nonvar(Term),
  124      Term = error(_, _)
  125    },
  126    [ 'Unknown exception: ~p'-[Term] ].
  127translate_message(Term) -->
  128    [ 'Unknown message: ~p'-[Term] ].
  129
  130translate_message2(Term) -->
  131    prolog_message(Term).
  132translate_message2(error(resource_error(stack), Context)) -->
  133    !,
  134    out_of_stack(Context).
  135translate_message2(error(resource_error(tripwire(Wire, Context)), _)) -->
  136    !,
  137    tripwire_message(Wire, Context).
  138translate_message2(error(existence_error(reset, Ball), SWI)) -->
  139    swi_location(SWI),
  140    tabling_existence_error(Ball, SWI).
  141translate_message2(error(ISO, SWI)) -->
  142    swi_location(SWI),
  143    term_message(ISO),
  144    swi_extra(SWI).
  145translate_message2('$aborted') -->
  146    [ 'Execution Aborted' ].
  147translate_message2(message_lines(Lines), L, T) :- % deal with old C-warning()
  148    make_message_lines(Lines, L, T).
  149translate_message2(format(Fmt, Args)) -->
  150    [ Fmt-Args ].
  151
  152make_message_lines([], T, T) :- !.
  153make_message_lines([Last],  ['~w'-[Last]|T], T) :- !.
  154make_message_lines([L0|LT], ['~w'-[L0],nl|T0], T) :-
  155    make_message_lines(LT, T0, T).
 term_message(+Term)//
Deal with the formal argument of error(Format, ImplDefined) exception terms. The ImplDefined argument is handled by swi_location//2.
  163:- public term_message//1.  164term_message(Term) -->
  165    {var(Term)},
  166    !,
  167    [ 'Unknown error term: ~p'-[Term] ].
  168term_message(Term) -->
  169    { message_lang(Lang) },
  170    prolog:error_message(Lang, Term),
  171    !.
  172term_message(Term) -->
  173    prolog:error_message(Term),
  174    !.
  175term_message(Term) -->
  176    iso_message(Term).
  177term_message(Term) -->
  178    swi_message(Term).
  179term_message(Term) -->
  180    [ 'Unknown error term: ~p'-[Term] ].
  181
  182iso_message(resource_error(c_stack)) -->
  183    out_of_c_stack.
  184iso_message(resource_error(Missing)) -->
  185    [ 'Not enough resources: ~w'-[Missing] ].
  186iso_message(type_error(evaluable, Actual)) -->
  187    { callable(Actual) },
  188    [ 'Arithmetic: `~p'' is not a function'-[Actual] ].
  189iso_message(type_error(free_of_attvar, Actual)) -->
  190    [ 'Type error: `~W'' contains attributed variables'-
  191      [Actual,[portray(true), attributes(portray)]] ].
  192iso_message(type_error(Expected, Actual)) -->
  193    [ 'Type error: `~w'' expected, found `~p'''-[Expected, Actual] ],
  194    type_error_comment(Expected, Actual).
  195iso_message(domain_error(Domain, Actual)) -->
  196    [ 'Domain error: '-[] ], domain(Domain),
  197    [ ' expected, found `~p'''-[Actual] ].
  198iso_message(instantiation_error) -->
  199    [ 'Arguments are not sufficiently instantiated' ].
  200iso_message(uninstantiation_error(Var)) -->
  201    [ 'Uninstantiated argument expected, found ~p'-[Var] ].
  202iso_message(representation_error(What)) -->
  203    [ 'Cannot represent due to `~w'''-[What] ].
  204iso_message(permission_error(Action, Type, Object)) -->
  205    permission_error(Action, Type, Object).
  206iso_message(evaluation_error(Which)) -->
  207    [ 'Arithmetic: evaluation error: `~p'''-[Which] ].
  208iso_message(existence_error(procedure, Proc)) -->
  209    [ 'Unknown procedure: ~q'-[Proc] ],
  210    unknown_proc_msg(Proc).
  211iso_message(existence_error(answer_variable, Var)) -->
  212    [ '$~w was not bound by a previous query'-[Var] ].
  213iso_message(existence_error(matching_rule, Goal)) -->
  214    [ 'No rule matches ~p'-[Goal] ].
  215iso_message(existence_error(Type, Object)) -->
  216    [ '~w `~p'' does not exist'-[Type, Object] ].
  217iso_message(existence_error(Type, Object, In)) --> % not ISO
  218    [ '~w `~p'' does not exist in ~p'-[Type, Object, In] ].
  219iso_message(busy(Type, Object)) -->
  220    [ '~w `~p'' is busy'-[Type, Object] ].
  221iso_message(syntax_error(swi_backslash_newline)) -->
  222    [ 'Deprecated ... \\<newline><white>*.  Use \\c' ].
  223iso_message(syntax_error(Id)) -->
  224    [ 'Syntax error: ' ],
  225    syntax_error(Id).
  226iso_message(occurs_check(Var, In)) -->
  227    [ 'Cannot unify ~p with ~p: would create an infinite tree'-[Var, In] ].
 permission_error(Action, Type, Object)//
Translate permission errors. Most follow te pattern "No permission to Action Type Object", but some are a bit different.
  234permission_error(Action, built_in_procedure, Pred) -->
  235    { user_predicate_indicator(Pred, PI)
  236    },
  237    [ 'No permission to ~w built-in predicate `~p'''-[Action, PI] ],
  238    (   {Action \== export}
  239    ->  [ nl,
  240          'Use :- redefine_system_predicate(+Head) if redefinition is intended'
  241        ]
  242    ;   []
  243    ).
  244permission_error(import_into(Dest), procedure, Pred) -->
  245    [ 'No permission to import ~p into ~w'-[Pred, Dest] ].
  246permission_error(Action, static_procedure, Proc) -->
  247    [ 'No permission to ~w static procedure `~p'''-[Action, Proc] ],
  248    defined_definition('Defined', Proc).
  249permission_error(input, stream, Stream) -->
  250    [ 'No permission to read from output stream `~p'''-[Stream] ].
  251permission_error(output, stream, Stream) -->
  252    [ 'No permission to write to input stream `~p'''-[Stream] ].
  253permission_error(input, text_stream, Stream) -->
  254    [ 'No permission to read bytes from TEXT stream `~p'''-[Stream] ].
  255permission_error(output, text_stream, Stream) -->
  256    [ 'No permission to write bytes to TEXT stream `~p'''-[Stream] ].
  257permission_error(input, binary_stream, Stream) -->
  258    [ 'No permission to read characters from binary stream `~p'''-[Stream] ].
  259permission_error(output, binary_stream, Stream) -->
  260    [ 'No permission to write characters to binary stream `~p'''-[Stream] ].
  261permission_error(open, source_sink, alias(Alias)) -->
  262    [ 'No permission to reuse alias "~p": already taken'-[Alias] ].
  263permission_error(tnot, non_tabled_procedure, Pred) -->
  264    [ 'The argument of tnot/1 is not tabled: ~p'-[Pred] ].
  265permission_error(assert, procedure, Pred) -->
  266    { '$pi_head'(Pred, Head),
  267      predicate_property(Head, ssu)
  268    },
  269    [ '~p: an SSU (Head => Body) predicate cannot have normal Prolog clauses'-
  270      [Pred] ].
  271permission_error(Action, Type, Object) -->
  272    [ 'No permission to ~w ~w `~p'''-[Action, Type, Object] ].
  273
  274
  275unknown_proc_msg(_:(^)/2) -->
  276    !,
  277    unknown_proc_msg((^)/2).
  278unknown_proc_msg((^)/2) -->
  279    !,
  280    [nl, '  ^/2 can only appear as the 2nd argument of setof/3 and bagof/3'].
  281unknown_proc_msg((:-)/2) -->
  282    !,
  283    [nl, '  Rules must be loaded from a file'],
  284    faq('ToplevelMode').
  285unknown_proc_msg((=>)/2) -->
  286    !,
  287    [nl, '  Rules must be loaded from a file'],
  288    faq('ToplevelMode').
  289unknown_proc_msg((:-)/1) -->
  290    !,
  291    [nl, '  Directives must be loaded from a file'],
  292    faq('ToplevelMode').
  293unknown_proc_msg((?-)/1) -->
  294    !,
  295    [nl, '  ?- is the Prolog prompt'],
  296    faq('ToplevelMode').
  297unknown_proc_msg(Proc) -->
  298    { dwim_predicates(Proc, Dwims) },
  299    (   {Dwims \== []}
  300    ->  [nl, '  However, there are definitions for:', nl],
  301        dwim_message(Dwims)
  302    ;   []
  303    ).
  304
  305dependency_error(shared(Shared), private(Private)) -->
  306    [ 'Shared table for ~p may not depend on private ~p'-[Shared, Private] ].
  307dependency_error(Dep, monotonic(On)) -->
  308    { '$pi_head'(PI, Dep),
  309      '$pi_head'(MPI, On)
  310    },
  311    [ 'Dependent ~p on monotonic predicate ~p is not monotonic or incremental'-
  312      [PI, MPI]
  313    ].
  314
  315faq(Page) -->
  316    [nl, '  See FAQ at https://www.swi-prolog.org/FAQ/', Page, '.txt' ].
  317
  318type_error_comment(_Expected, Actual) -->
  319    { type_of(Actual, Type),
  320      (   sub_atom(Type, 0, 1, _, First),
  321          memberchk(First, [a,e,i,o,u])
  322      ->  Article = an
  323      ;   Article = a
  324      )
  325    },
  326    [ ' (~w ~w)'-[Article, Type] ].
  327
  328type_of(Term, Type) :-
  329    (   attvar(Term)      -> Type = attvar
  330    ;   var(Term)         -> Type = var
  331    ;   atom(Term)        -> Type = atom
  332    ;   integer(Term)     -> Type = integer
  333    ;   string(Term)      -> Type = string
  334    ;   Term == []        -> Type = empty_list
  335    ;   blob(Term, BlobT) -> blob_type(BlobT, Type)
  336    ;   rational(Term)    -> Type = rational
  337    ;   float(Term)       -> Type = float
  338    ;   is_stream(Term)   -> Type = stream
  339    ;   is_dict(Term)     -> Type = dict
  340    ;   is_list(Term)     -> Type = list
  341    ;   cyclic_term(Term) -> Type = cyclic
  342    ;   compound(Term)    -> Type = compound
  343    ;                        Type = unknown
  344    ).
  345
  346blob_type(BlobT, Type) :-
  347    atom_concat(BlobT, '_reference', Type).
  348
  349syntax_error(end_of_clause) -->
  350    [ 'Unexpected end of clause' ].
  351syntax_error(end_of_clause_expected) -->
  352    [ 'End of clause expected' ].
  353syntax_error(end_of_file) -->
  354    [ 'Unexpected end of file' ].
  355syntax_error(end_of_file_in_block_comment) -->
  356    [ 'End of file in /* ... */ comment' ].
  357syntax_error(end_of_file_in_quoted(Quote)) -->
  358    [ 'End of file in quoted ' ],
  359    quoted_type(Quote).
  360syntax_error(illegal_number) -->
  361    [ 'Illegal number' ].
  362syntax_error(long_atom) -->
  363    [ 'Atom too long (see style_check/1)' ].
  364syntax_error(long_string) -->
  365    [ 'String too long (see style_check/1)' ].
  366syntax_error(operator_clash) -->
  367    [ 'Operator priority clash' ].
  368syntax_error(operator_expected) -->
  369    [ 'Operator expected' ].
  370syntax_error(operator_balance) -->
  371    [ 'Unbalanced operator' ].
  372syntax_error(quoted_punctuation) -->
  373    [ 'Operand expected, unquoted comma or bar found' ].
  374syntax_error(list_rest) -->
  375    [ 'Unexpected comma or bar in rest of list' ].
  376syntax_error(cannot_start_term) -->
  377    [ 'Illegal start of term' ].
  378syntax_error(punct(Punct, End)) -->
  379    [ 'Unexpected `~w\' before `~w\''-[Punct, End] ].
  380syntax_error(undefined_char_escape(C)) -->
  381    [ 'Unknown character escape in quoted atom or string: `\\~w\''-[C] ].
  382syntax_error(void_not_allowed) -->
  383    [ 'Empty argument list "()"' ].
  384syntax_error(Message) -->
  385    [ '~w'-[Message] ].
  386
  387quoted_type('\'') --> [atom].
  388quoted_type('\"') --> { current_prolog_flag(double_quotes, Type) }, [Type-[]].
  389quoted_type('\`') --> { current_prolog_flag(back_quotes, Type) }, [Type-[]].
  390
  391domain(range(Low,High)) -->
  392    !,
  393    ['[~q..~q]'-[Low,High] ].
  394domain(Domain) -->
  395    ['`~w\''-[Domain] ].
 tabling_existence_error(+Ball, +Context)//
Called on invalid shift/1 calls. Track those that result from tabling errors.
  402tabling_existence_error(Ball, Context) -->
  403    { table_shift_ball(Ball) },
  404    [ 'Tabling dependency error' ],
  405    swi_extra(Context).
  406
  407table_shift_ball(dependency(_Head)).
  408table_shift_ball(dependency(_Skeleton, _Trie, _Mono)).
  409table_shift_ball(call_info(_Skeleton, _Status)).
  410table_shift_ball(call_info(_GenSkeleton, _Skeleton, _Status)).
 dwim_predicates(+PI, -Dwims)
Find related predicate indicators.
  416dwim_predicates(Module:Name/_Arity, Dwims) :-
  417    !,
  418    findall(Dwim, dwim_predicate(Module:Name, Dwim), Dwims).
  419dwim_predicates(Name/_Arity, Dwims) :-
  420    findall(Dwim, dwim_predicate(user:Name, Dwim), Dwims).
  421
  422dwim_message([]) --> [].
  423dwim_message([M:Head|T]) -->
  424    { hidden_module(M),
  425      !,
  426      functor(Head, Name, Arity)
  427    },
  428    [ '        ~q'-[Name/Arity], nl ],
  429    dwim_message(T).
  430dwim_message([Module:Head|T]) -->
  431    !,
  432    { functor(Head, Name, Arity)
  433    },
  434    [ '        ~q'-[Module:Name/Arity], nl],
  435    dwim_message(T).
  436dwim_message([Head|T]) -->
  437    {functor(Head, Name, Arity)},
  438    [ '        ~q'-[Name/Arity], nl],
  439    dwim_message(T).
  440
  441
  442swi_message(io_error(Op, Stream)) -->
  443    [ 'I/O error in ~w on stream ~p'-[Op, Stream] ].
  444swi_message(thread_error(TID, false)) -->
  445    [ 'Thread ~p died due to failure:'-[TID] ].
  446swi_message(thread_error(TID, exception(Error))) -->
  447    [ 'Thread ~p died abnormally:'-[TID], nl ],
  448    translate_message(Error).
  449swi_message(dependency_error(Tabled, DependsOn)) -->
  450    dependency_error(Tabled, DependsOn).
  451swi_message(shell(execute, Cmd)) -->
  452    [ 'Could not execute `~w'''-[Cmd] ].
  453swi_message(shell(signal(Sig), Cmd)) -->
  454    [ 'Caught signal ~d on `~w'''-[Sig, Cmd] ].
  455swi_message(format(Fmt, Args)) -->
  456    [ Fmt-Args ].
  457swi_message(signal(Name, Num)) -->
  458    [ 'Caught signal ~d (~w)'-[Num, Name] ].
  459swi_message(limit_exceeded(Limit, MaxVal)) -->
  460    [ 'Exceeded ~w limit (~w)'-[Limit, MaxVal] ].
  461swi_message(goal_failed(Goal)) -->
  462    [ 'goal unexpectedly failed: ~p'-[Goal] ].
  463swi_message(shared_object(_Action, Message)) --> % Message = dlerror()
  464    [ '~w'-[Message] ].
  465swi_message(system_error(Error)) -->
  466    [ 'error in system call: ~w'-[Error]
  467    ].
  468swi_message(system_error) -->
  469    [ 'error in system call'
  470    ].
  471swi_message(failure_error(Goal)) -->
  472    [ 'Goal failed: ~p'-[Goal] ].
  473swi_message(timeout_error(Op, Stream)) -->
  474    [ 'Timeout in ~w from ~p'-[Op, Stream] ].
  475swi_message(not_implemented(Type, What)) -->
  476    [ '~w `~p\' is not implemented in this version'-[Type, What] ].
  477swi_message(context_error(nodirective, Goal)) -->
  478    { goal_to_predicate_indicator(Goal, PI) },
  479    [ 'Wrong context: ~p can only be used in a directive'-[PI] ].
  480swi_message(context_error(edit, no_default_file)) -->
  481    (   { current_prolog_flag(windows, true) }
  482    ->  [ 'Edit/0 can only be used after opening a \c
  483               Prolog file by double-clicking it' ]
  484    ;   [ 'Edit/0 can only be used with the "-s file" commandline option'
  485        ]
  486    ),
  487    [ nl, 'Use "?- edit(Topic)." or "?- emacs."' ].
  488swi_message(context_error(function, meta_arg(S))) -->
  489    [ 'Functions are not (yet) supported for meta-arguments of type ~q'-[S] ].
  490swi_message(format_argument_type(Fmt, Arg)) -->
  491    [ 'Illegal argument to format sequence ~~~w: ~p'-[Fmt, Arg] ].
  492swi_message(format(Msg)) -->
  493    [ 'Format error: ~w'-[Msg] ].
  494swi_message(conditional_compilation_error(unterminated, File:Line)) -->
  495    [ 'Unterminated conditional compilation from '-[], url(File:Line) ].
  496swi_message(conditional_compilation_error(no_if, What)) -->
  497    [ ':- ~w without :- if'-[What] ].
  498swi_message(duplicate_key(Key)) -->
  499    [ 'Duplicate key: ~p'-[Key] ].
  500swi_message(initialization_error(failed, Goal, File:Line)) -->
  501    !,
  502    [ url(File:Line), ': ~p: false'-[Goal] ].
  503swi_message(initialization_error(Error, Goal, File:Line)) -->
  504    [ url(File:Line), ': ~p '-[Goal] ],
  505    translate_message(Error).
  506swi_message(determinism_error(PI, det, Found, property)) -->
  507    (   { '$pi_head'(user:PI, Head),
  508          predicate_property(Head, det)
  509        }
  510    ->  [ 'Deterministic procedure ~p'-[PI] ]
  511    ;   [ 'Procedure ~p called from a deterministic procedure'-[PI] ]
  512    ),
  513    det_error(Found).
  514swi_message(determinism_error(PI, det, fail, guard)) -->
  515    [ 'Procedure ~p failed after $-guard'-[PI] ].
  516swi_message(determinism_error(PI, det, fail, guard_in_caller)) -->
  517    [ 'Procedure ~p failed after $-guard in caller'-[PI] ].
  518swi_message(determinism_error(Goal, det, fail, goal)) -->
  519    [ 'Goal ~p failed'-[Goal] ].
  520swi_message(determinism_error(Goal, det, nondet, goal)) -->
  521    [ 'Goal ~p succeeded with a choice point'-[Goal] ].
  522swi_message(qlf_format_error(File, Message)) -->
  523    [ '~w: Invalid QLF file: ~w'-[File, Message] ].
  524swi_message(goal_expansion_error(bound, Term)) -->
  525    [ 'Goal expansion bound a variable to ~p'-[Term] ].
  526
  527det_error(nondet) -->
  528    [ ' succeeded with a choicepoint'- [] ].
  529det_error(fail) -->
  530    [ ' failed'- [] ].
 swi_location(+Term)// is det
Print location information for error(Formal, ImplDefined) from the ImplDefined term.
  538:- public swi_location//1.  539swi_location(X) -->
  540    { var(X) },
  541    !.
  542swi_location(Context) -->
  543    { message_lang(Lang) },
  544    prolog:message_location(Lang, Context),
  545    !.
  546swi_location(Context) -->
  547    prolog:message_location(Context),
  548    !.
  549swi_location(context(Caller, _Msg)) -->
  550    { ground(Caller) },
  551    !,
  552    caller(Caller).
  553swi_location(file(Path, Line, -1, _CharNo)) -->
  554    !,
  555    [ url(Path:Line), ': ' ].
  556swi_location(file(Path, Line, LinePos, _CharNo)) -->
  557    [ url(Path:Line:LinePos), ': ' ].
  558swi_location(stream(Stream, Line, LinePos, CharNo)) -->
  559    (   { is_stream(Stream),
  560          stream_property(Stream, file_name(File))
  561        }
  562    ->  swi_location(file(File, Line, LinePos, CharNo))
  563    ;   [ 'Stream ~w:~d:~d '-[Stream, Line, LinePos] ]
  564    ).
  565swi_location(autoload(File:Line)) -->
  566    [ url(File:Line), ': ' ].
  567swi_location(_) -->
  568    [].
  569
  570caller(system:'$record_clause'/3) -->
  571    !,
  572    [].
  573caller(Module:Name/Arity) -->
  574    !,
  575    (   { \+ hidden_module(Module) }
  576    ->  [ '~q:~q/~w: '-[Module, Name, Arity] ]
  577    ;   [ '~q/~w: '-[Name, Arity] ]
  578    ).
  579caller(Name/Arity) -->
  580    [ '~q/~w: '-[Name, Arity] ].
  581caller(Caller) -->
  582    [ '~p: '-[Caller] ].
 swi_extra(+Term)// is det
Extract information from the second argument of an error(Formal, ImplDefined) that is printed after the core of the message.
See also
- swi_location//1 uses the same term to insert context before the core of the message.
  593swi_extra(X) -->
  594    { var(X) },
  595    !,
  596    [].
  597swi_extra(Context) -->
  598    { message_lang(Lang) },
  599    prolog:message_context(Lang, Context),
  600    !.
  601swi_extra(Context) -->
  602    prolog:message_context(Context).
  603swi_extra(context(_, Msg)) -->
  604    { nonvar(Msg),
  605      Msg \== ''
  606    },
  607    !,
  608    swi_comment(Msg).
  609swi_extra(string(String, CharPos)) -->
  610    { sub_string(String, 0, CharPos, _, Before),
  611      sub_string(String, CharPos, _, 0, After)
  612    },
  613    [ nl, '~w'-[Before], nl, '** here **', nl, '~w'-[After] ].
  614swi_extra(_) -->
  615    [].
  616
  617swi_comment(already_from(Module)) -->
  618    !,
  619    [ ' (already imported from ~q)'-[Module] ].
  620swi_comment(directory(_Dir)) -->
  621    !,
  622    [ ' (is a directory)' ].
  623swi_comment(not_a_directory(_Dir)) -->
  624    !,
  625    [ ' (is not a directory)' ].
  626swi_comment(Msg) -->
  627    [ ' (~w)'-[Msg] ].
  628
  629
  630thread_context -->
  631    { thread_self(Me), Me \== main, thread_property(Me, id(Id)) },
  632    !,
  633    ['[Thread ~w] '-[Id]].
  634thread_context -->
  635    [].
  636
  637                 /*******************************
  638                 *        NORMAL MESSAGES       *
  639                 *******************************/
  640
  641prolog_message(welcome) -->
  642    [ 'Welcome to SWI-Prolog (' ],
  643    prolog_message(threads),
  644    prolog_message(address_bits),
  645    ['version ' ],
  646    prolog_message(version),
  647    [ ')', nl ],
  648    prolog_message(copyright),
  649    [ nl ],
  650    translate_message(user_versions),
  651    [ nl ],
  652    prolog_message(documentaton),
  653    [ nl, nl ].
  654prolog_message(user_versions) -->
  655    (   { findall(Msg, prolog:version_msg(Msg), Msgs),
  656          Msgs \== []
  657        }
  658    ->  [nl],
  659        user_version_messages(Msgs)
  660    ;   []
  661    ).
  662prolog_message(deprecated(Term)) -->
  663    { nonvar(Term) },
  664    (   { message_lang(Lang) },
  665        prolog:deprecated(Lang, Term)
  666    ->  []
  667    ;   prolog:deprecated(Term)
  668    ->  []
  669    ;   deprecated(Term)
  670    ).
  671prolog_message(unhandled_exception(E)) -->
  672    { nonvar(E) },
  673    [ 'Unhandled exception: ' ],
  674    (   translate_message(E)
  675    ->  []
  676    ;   [ '~p'-[E] ]
  677    ).
 prolog_message(+Term)//
  681prolog_message(initialization_error(_, E, File:Line)) -->
  682    !,
  683    [ url(File:Line),
  684      ': Initialization goal raised exception:', nl
  685    ],
  686    translate_message(E).
  687prolog_message(initialization_error(Goal, E, _)) -->
  688    [ 'Initialization goal ~p raised exception:'-[Goal], nl ],
  689    translate_message(E).
  690prolog_message(initialization_failure(_Goal, File:Line)) -->
  691    !,
  692    [ url(File:Line),
  693      ': Initialization goal failed'-[]
  694    ].
  695prolog_message(initialization_failure(Goal, _)) -->
  696    [ 'Initialization goal failed: ~p'-[Goal]
  697    ].
  698prolog_message(initialization_exception(E)) -->
  699    [ 'Prolog initialisation failed:', nl ],
  700    translate_message(E).
  701prolog_message(init_goal_syntax(Error, Text)) -->
  702    !,
  703    [ '-g ~w: '-[Text] ],
  704    translate_message(Error).
  705prolog_message(init_goal_failed(failed, @(Goal,File:Line))) -->
  706    !,
  707    [ url(File:Line), ': ~p: false'-[Goal] ].
  708prolog_message(init_goal_failed(Error, @(Goal,File:Line))) -->
  709    !,
  710    [ url(File:Line), ': ~p '-[Goal] ],
  711    translate_message(Error).
  712prolog_message(init_goal_failed(failed, Text)) -->
  713    !,
  714    [ '-g ~w: false'-[Text] ].
  715prolog_message(init_goal_failed(Error, Text)) -->
  716    !,
  717    [ '-g ~w: '-[Text] ],
  718    translate_message(Error).
  719prolog_message(goal_failed(Context, Goal)) -->
  720    [ 'Goal (~w) failed: ~p'-[Context, Goal] ].
  721prolog_message(no_current_module(Module)) -->
  722    [ '~w is not a current module (created)'-[Module] ].
  723prolog_message(commandline_arg_type(Flag, Arg)) -->
  724    [ 'Bad argument to commandline option -~w: ~w'-[Flag, Arg] ].
  725prolog_message(missing_feature(Name)) -->
  726    [ 'This version of SWI-Prolog does not support ~w'-[Name] ].
  727prolog_message(singletons(_Term, List)) -->
  728    [ 'Singleton variables: ~w'-[List] ].
  729prolog_message(multitons(_Term, List)) -->
  730    [ 'Singleton-marked variables appearing more than once: ~w'-[List] ].
  731prolog_message(profile_no_cpu_time) -->
  732    [ 'No CPU-time info.  Check the SWI-Prolog manual for details' ].
  733prolog_message(non_ascii(Text, Type)) -->
  734    [ 'Unquoted ~w with non-portable characters: ~w'-[Type, Text] ].
  735prolog_message(io_warning(Stream, Message)) -->
  736    { stream_property(Stream, position(Position)),
  737      !,
  738      stream_position_data(line_count, Position, LineNo),
  739      stream_position_data(line_position, Position, LinePos),
  740      (   stream_property(Stream, file_name(File))
  741      ->  Obj = File
  742      ;   Obj = Stream
  743      )
  744    },
  745    [ '~p:~d:~d: ~w'-[Obj, LineNo, LinePos, Message] ].
  746prolog_message(io_warning(Stream, Message)) -->
  747    [ 'stream ~p: ~w'-[Stream, Message] ].
  748prolog_message(option_usage(pldoc)) -->
  749    [ 'Usage: --pldoc[=port]' ].
  750prolog_message(interrupt(begin)) -->
  751    [ 'Action (h for help) ? ', flush ].
  752prolog_message(interrupt(end)) -->
  753    [ 'continue' ].
  754prolog_message(interrupt(trace)) -->
  755    [ 'continue (trace mode)' ].
  756prolog_message(unknown_in_module_user) -->
  757    [ 'Using a non-error value for unknown in the global module', nl,
  758      'causes most of the development environment to stop working.', nl,
  759      'Please use :- dynamic or limit usage of unknown to a module.', nl,
  760      'See https://www.swi-prolog.org/howto/database.html'
  761    ].
  762prolog_message(untable(PI)) -->
  763    [ 'Reconsult: removed tabling for ~p'-[PI] ].
  764
  765
  766                 /*******************************
  767                 *         LOADING FILES        *
  768                 *******************************/
  769
  770prolog_message(modify_active_procedure(Who, What)) -->
  771    [ '~p: modified active procedure ~p'-[Who, What] ].
  772prolog_message(load_file(failed(user:File))) -->
  773    [ 'Failed to load ~p'-[File] ].
  774prolog_message(load_file(failed(Module:File))) -->
  775    [ 'Failed to load ~p into module ~p'-[File, Module] ].
  776prolog_message(load_file(failed(File))) -->
  777    [ 'Failed to load ~p'-[File] ].
  778prolog_message(mixed_directive(Goal)) -->
  779    [ 'Cannot pre-compile mixed load/call directive: ~p'-[Goal] ].
  780prolog_message(cannot_redefine_comma) -->
  781    [ 'Full stop in clause-body?  Cannot redefine ,/2' ].
  782prolog_message(illegal_autoload_index(Dir, Term)) -->
  783    [ 'Illegal term in INDEX file of directory ~w: ~w'-[Dir, Term] ].
  784prolog_message(redefined_procedure(Type, Proc)) -->
  785    [ 'Redefined ~w procedure ~p'-[Type, Proc] ],
  786    defined_definition('Previously defined', Proc).
  787prolog_message(declare_module(Module, abolish(Predicates))) -->
  788    [ 'Loading module ~w abolished: ~p'-[Module, Predicates] ].
  789prolog_message(import_private(Module, Private)) -->
  790    [ 'import/1: ~p is not exported (still imported into ~q)'-
  791      [Private, Module]
  792    ].
  793prolog_message(ignored_weak_import(Into, From:PI)) -->
  794    [ 'Local definition of ~p overrides weak import from ~q'-
  795      [Into:PI, From]
  796    ].
  797prolog_message(undefined_export(Module, PI)) -->
  798    [ 'Exported procedure ~q:~q is not defined'-[Module, PI] ].
  799prolog_message(no_exported_op(Module, Op)) -->
  800    [ 'Operator ~q:~q is not exported (still defined)'-[Module, Op] ].
  801prolog_message(discontiguous((-)/2,_)) -->
  802    prolog_message(minus_in_identifier).
  803prolog_message(discontiguous(Proc,Current)) -->
  804    [ 'Clauses of ', ansi(code, '~p', [Proc]),
  805      ' are not together in the source-file', nl ],
  806    current_definition(Proc, 'Earlier definition at '),
  807    [ 'Current predicate: ', ansi(code, '~p', [Current]), nl,
  808      'Use ', ansi(code, ':- discontiguous ~p.', [Proc]),
  809      ' to suppress this message'
  810    ].
  811prolog_message(decl_no_effect(Goal)) -->
  812    [ 'Deprecated declaration has no effect: ~p'-[Goal] ].
  813prolog_message(load_file(start(Level, File))) -->
  814    [ '~|~t~*+Loading '-[Level] ],
  815    load_file(File),
  816    [ ' ...' ].
  817prolog_message(include_file(start(Level, File))) -->
  818    [ '~|~t~*+include '-[Level] ],
  819    load_file(File),
  820    [ ' ...' ].
  821prolog_message(include_file(done(Level, File))) -->
  822    [ '~|~t~*+included '-[Level] ],
  823    load_file(File).
  824prolog_message(load_file(done(Level, File, Action, Module, Time, Clauses))) -->
  825    [ '~|~t~*+'-[Level] ],
  826    load_file(File),
  827    [ ' ~w'-[Action] ],
  828    load_module(Module),
  829    [ ' ~2f sec, ~D clauses'-[Time, Clauses] ].
  830prolog_message(dwim_undefined(Goal, Alternatives)) -->
  831    { goal_to_predicate_indicator(Goal, Pred)
  832    },
  833    [ 'Unknown procedure: ~q'-[Pred], nl,
  834      '    However, there are definitions for:', nl
  835    ],
  836    dwim_message(Alternatives).
  837prolog_message(dwim_correct(Into)) -->
  838    [ 'Correct to: ~q? '-[Into], flush ].
  839prolog_message(error(loop_error(Spec), file_search(Used))) -->
  840    [ 'File search: too many levels of indirections on: ~p'-[Spec], nl,
  841      '    Used alias expansions:', nl
  842    ],
  843    used_search(Used).
  844prolog_message(minus_in_identifier) -->
  845    [ 'The "-" character should not be used to separate words in an', nl,
  846      'identifier.  Check the SWI-Prolog FAQ for details.'
  847    ].
  848prolog_message(qlf(removed_after_error(File))) -->
  849    [ 'Removed incomplete QLF file ~w'-[File] ].
  850prolog_message(qlf(recompile(Spec,_Pl,_Qlf,Reason))) -->
  851    [ '~p: recompiling QLF file'-[Spec] ],
  852    qlf_recompile_reason(Reason).
  853prolog_message(qlf(can_not_recompile(Spec,QlfFile,_Reason))) -->
  854    [ '~p: can not recompile "~w" (access denied)'-[Spec, QlfFile], nl,
  855      '\tLoading from source'-[]
  856    ].
  857prolog_message(qlf(system_lib_out_of_date(Spec,QlfFile))) -->
  858    [ '~p: can not recompile "~w" (access denied)'-[Spec, QlfFile], nl,
  859      '\tLoading QlfFile'-[]
  860    ].
  861prolog_message(redefine_module(Module, OldFile, File)) -->
  862    [ 'Module "~q" already loaded from ~w.'-[Module, OldFile], nl,
  863      'Wipe and reload from ~w? '-[File], flush
  864    ].
  865prolog_message(redefine_module_reply) -->
  866    [ 'Please answer y(es), n(o) or a(bort)' ].
  867prolog_message(reloaded_in_module(Absolute, OldContext, LM)) -->
  868    [ '~w was previously loaded in module ~w'-[Absolute, OldContext], nl,
  869      '\tnow it is reloaded into module ~w'-[LM] ].
  870prolog_message(expected_layout(Expected, Pos)) -->
  871    [ 'Layout data: expected ~w, found: ~p'-[Expected, Pos] ].
  872
  873defined_definition(Message, Spec) -->
  874    { strip_module(user:Spec, M, Name/Arity),
  875      functor(Head, Name, Arity),
  876      predicate_property(M:Head, file(File)),
  877      predicate_property(M:Head, line_count(Line))
  878    },
  879    !,
  880    [ nl, '~w at '-[Message], url(File:Line) ].
  881defined_definition(_, _) --> [].
  882
  883used_search([]) -->
  884    [].
  885used_search([Alias=Expanded|T]) -->
  886    [ '        file_search_path(~p, ~p)'-[Alias, Expanded], nl ],
  887    used_search(T).
  888
  889load_file(file(Spec, _Path)) -->
  890    (   {atomic(Spec)}
  891    ->  [ '~w'-[Spec] ]
  892    ;   [ '~p'-[Spec] ]
  893    ).
  894%load_file(file(_, Path)) -->
  895%       [ '~w'-[Path] ].
  896
  897load_module(user) --> !.
  898load_module(system) --> !.
  899load_module(Module) -->
  900    [ ' into ~w'-[Module] ].
  901
  902goal_to_predicate_indicator(Goal, PI) :-
  903    strip_module(Goal, Module, Head),
  904    callable_name_arity(Head, Name, Arity),
  905    user_predicate_indicator(Module:Name/Arity, PI).
  906
  907callable_name_arity(Goal, Name, Arity) :-
  908    compound(Goal),
  909    !,
  910    compound_name_arity(Goal, Name, Arity).
  911callable_name_arity(Goal, Goal, 0) :-
  912    atom(Goal).
  913
  914user_predicate_indicator(Module:PI, PI) :-
  915    hidden_module(Module),
  916    !.
  917user_predicate_indicator(PI, PI).
  918
  919hidden_module(user) :- !.
  920hidden_module(system) :- !.
  921hidden_module(M) :-
  922    sub_atom(M, 0, _, _, $).
  923
  924current_definition(Proc, Prefix) -->
  925    { pi_uhead(Proc, Head),
  926      predicate_property(Head, file(File)),
  927      predicate_property(Head, line_count(Line))
  928    },
  929    [ '~w'-[Prefix], url(File:Line), nl ].
  930current_definition(_, _) --> [].
  931
  932pi_uhead(Module:Name/Arity, Module:Head) :-
  933    !,
  934    atom(Module), atom(Name), integer(Arity),
  935    functor(Head, Name, Arity).
  936pi_uhead(Name/Arity, user:Head) :-
  937    atom(Name), integer(Arity),
  938    functor(Head, Name, Arity).
  939
  940qlf_recompile_reason(old) -->
  941    !,
  942    [ ' (out of date)'-[] ].
  943qlf_recompile_reason(_) -->
  944    [ ' (incompatible with current Prolog version)'-[] ].
  945
  946prolog_message(file_search(cache(Spec, _Cond), Path)) -->
  947    [ 'File search: ~p --> ~p (cache)'-[Spec, Path] ].
  948prolog_message(file_search(found(Spec, Cond), Path)) -->
  949    [ 'File search: ~p --> ~p OK ~p'-[Spec, Path, Cond] ].
  950prolog_message(file_search(tried(Spec, Cond), Path)) -->
  951    [ 'File search: ~p --> ~p NO ~p'-[Spec, Path, Cond] ].
  952
  953                 /*******************************
  954                 *              GC              *
  955                 *******************************/
  956
  957prolog_message(agc(start)) -->
  958    thread_context,
  959    [ 'AGC: ', flush ].
  960prolog_message(agc(done(Collected, Remaining, Time))) -->
  961    [ at_same_line,
  962      'reclaimed ~D atoms in ~3f sec. (remaining: ~D)'-
  963      [Collected, Time, Remaining]
  964    ].
  965prolog_message(cgc(start)) -->
  966    thread_context,
  967    [ 'CGC: ', flush ].
  968prolog_message(cgc(done(CollectedClauses, _CollectedBytes,
  969                        RemainingBytes, Time))) -->
  970    [ at_same_line,
  971      'reclaimed ~D clauses in ~3f sec. (pending: ~D bytes)'-
  972      [CollectedClauses, Time, RemainingBytes]
  973    ].
  974
  975		 /*******************************
  976		 *        STACK OVERFLOW	*
  977		 *******************************/
  978
  979out_of_stack(Context) -->
  980    { human_stack_size(Context.localused,   Local),
  981      human_stack_size(Context.globalused,  Global),
  982      human_stack_size(Context.trailused,   Trail),
  983      human_stack_size(Context.stack_limit, Limit),
  984      LCO is (100*(Context.depth - Context.environments))/Context.depth
  985    },
  986    [ 'Stack limit (~s) exceeded'-[Limit], nl,
  987      '  Stack sizes: local: ~s, global: ~s, trail: ~s'-[Local,Global,Trail], nl,
  988      '  Stack depth: ~D, last-call: ~0f%, Choice points: ~D'-
  989         [Context.depth, LCO, Context.choicepoints], nl
  990    ],
  991    overflow_reason(Context, Resolve),
  992    resolve_overflow(Resolve).
  993
  994human_stack_size(Size, String) :-
  995    Size < 100,
  996    format(string(String), '~dKb', [Size]).
  997human_stack_size(Size, String) :-
  998    Size < 100 000,
  999    Value is Size / 1024,
 1000    format(string(String), '~1fMb', [Value]).
 1001human_stack_size(Size, String) :-
 1002    Value is Size / (1024*1024),
 1003    format(string(String), '~1fGb', [Value]).
 1004
 1005overflow_reason(Context, fix) -->
 1006    show_non_termination(Context),
 1007    !.
 1008overflow_reason(Context, enlarge) -->
 1009    { Stack = Context.get(stack) },
 1010    !,
 1011    [ '  In:'-[], nl ],
 1012    stack(Stack).
 1013overflow_reason(_Context, enlarge) -->
 1014    [ '  Insufficient global stack'-[] ].
 1015
 1016show_non_termination(Context) -->
 1017    (   { Stack = Context.get(cycle) }
 1018    ->  [ '  Probable infinite recursion (cycle):'-[], nl ]
 1019    ;   { Stack = Context.get(non_terminating) }
 1020    ->  [ '  Possible non-terminating recursion:'-[], nl ]
 1021    ),
 1022    stack(Stack).
 1023
 1024stack([]) --> [].
 1025stack([frame(Depth, M:Goal, _)|T]) -->
 1026    [ '    [~D] ~q:'-[Depth, M] ],
 1027    stack_goal(Goal),
 1028    [ nl ],
 1029    stack(T).
 1030
 1031stack_goal(Goal) -->
 1032    { compound(Goal),
 1033      !,
 1034      compound_name_arity(Goal, Name, Arity)
 1035    },
 1036    [ '~q('-[Name] ],
 1037    stack_goal_args(1, Arity, Goal),
 1038    [ ')'-[] ].
 1039stack_goal(Goal) -->
 1040    [ '~q'-[Goal] ].
 1041
 1042stack_goal_args(I, Arity, Goal) -->
 1043    { I =< Arity,
 1044      !,
 1045      arg(I, Goal, A),
 1046      I2 is I + 1
 1047    },
 1048    stack_goal_arg(A),
 1049    (   { I2 =< Arity }
 1050    ->  [ ', '-[] ],
 1051        stack_goal_args(I2, Arity, Goal)
 1052    ;   []
 1053    ).
 1054stack_goal_args(_, _, _) -->
 1055    [].
 1056
 1057stack_goal_arg(A) -->
 1058    { nonvar(A),
 1059      A = [Len|T],
 1060      !
 1061    },
 1062    (   {Len == cyclic_term}
 1063    ->  [ '[cyclic list]'-[] ]
 1064    ;   {T == []}
 1065    ->  [ '[length:~D]'-[Len] ]
 1066    ;   [ '[length:~D|~p]'-[Len, T] ]
 1067    ).
 1068stack_goal_arg(A) -->
 1069    { nonvar(A),
 1070      A = _/_,
 1071      !
 1072    },
 1073    [ '<compound ~p>'-[A] ].
 1074stack_goal_arg(A) -->
 1075    [ '~p'-[A] ].
 1076
 1077resolve_overflow(fix) -->
 1078    [].
 1079resolve_overflow(enlarge) -->
 1080    { current_prolog_flag(stack_limit, LimitBytes),
 1081      NewLimit is LimitBytes * 2
 1082    },
 1083    [ nl,
 1084      'Use the --stack_limit=size[KMG] command line option or'-[], nl,
 1085      '?- set_prolog_flag(stack_limit, ~I). to double the limit.'-[NewLimit]
 1086    ].
 out_of_c_stack
The thread's C-stack limit was exceeded. Give some advice on how to resolve this.
 1093out_of_c_stack -->
 1094    { statistics(c_stack, Limit), Limit > 0 },
 1095    !,
 1096    [ 'C-stack limit (~D bytes) exceeded.'-[Limit], nl ],
 1097    resolve_c_stack_overflow(Limit).
 1098out_of_c_stack -->
 1099    { statistics(c_stack, Limit), Limit > 0 },
 1100    [ 'C-stack limit exceeded.'-[Limit], nl ],
 1101    resolve_c_stack_overflow(Limit).
 1102
 1103resolve_c_stack_overflow(_Limit) -->
 1104    { thread_self(main) },
 1105    [ 'Use the shell command ' ], code('~w', 'ulimit -s size'),
 1106    [ ' to enlarge the limit.' ].
 1107resolve_c_stack_overflow(_Limit) -->
 1108    [ 'Use the ' ], code('~w', 'c_stack(KBytes)'),
 1109    [ ' option of '], code(thread_create/3), [' to enlarge the limit.' ].
 1110
 1111
 1112                 /*******************************
 1113                 *        MAKE/AUTOLOAD         *
 1114                 *******************************/
 1115
 1116prolog_message(make(reload(Files))) -->
 1117    { length(Files, N)
 1118    },
 1119    [ 'Make: reloading ~D files'-[N] ].
 1120prolog_message(make(done(_Files))) -->
 1121    [ 'Make: finished' ].
 1122prolog_message(make(library_index(Dir))) -->
 1123    [ 'Updating index for library ~w'-[Dir] ].
 1124prolog_message(autoload(Pred, File)) -->
 1125    thread_context,
 1126    [ 'autoloading ~p from ~w'-[Pred, File] ].
 1127prolog_message(autoload(read_index(Dir))) -->
 1128    [ 'Loading autoload index for ~w'-[Dir] ].
 1129prolog_message(autoload(disabled(Loaded))) -->
 1130    [ 'Disabled autoloading (loaded ~D files)'-[Loaded] ].
 1131prolog_message(autoload(already_defined(PI, From))) -->
 1132    code(PI),
 1133    (   { '$pi_head'(PI, Head),
 1134          predicate_property(Head, built_in)
 1135        }
 1136    ->  [' is a built-in predicate']
 1137    ;   [ ' is already imported from module ' ],
 1138        code(From)
 1139    ).
 1140
 1141swi_message(autoload(Msg)) -->
 1142    [ nl, '  ' ],
 1143    autoload_message(Msg).
 1144
 1145autoload_message(not_exported(PI, Spec, _FullFile, _Exports)) -->
 1146    [ ansi(code, '~w', [Spec]),
 1147      ' does not export ',
 1148      ansi(code, '~p', [PI])
 1149    ].
 1150autoload_message(no_file(Spec)) -->
 1151    [ ansi(code, '~p', [Spec]), ': No such file' ].
 1152
 1153
 1154                 /*******************************
 1155                 *       COMPILER WARNINGS      *
 1156                 *******************************/
 1157
 1158% print warnings about dubious code raised by the compiler.
 1159% TBD: pass in PC to produce exact error locations.
 1160
 1161prolog_message(compiler_warnings(Clause, Warnings0)) -->
 1162    {   print_goal_options(DefOptions),
 1163        (   prolog_load_context(variable_names, VarNames)
 1164        ->  warnings_with_named_vars(Warnings0, VarNames, Warnings),
 1165            Options = [variable_names(VarNames)|DefOptions]
 1166        ;   Options = DefOptions,
 1167            Warnings = Warnings0
 1168        )
 1169    },
 1170    compiler_warnings(Warnings, Clause, Options).
 1171
 1172warnings_with_named_vars([], _, []).
 1173warnings_with_named_vars([H|T0], VarNames, [H|T]) :-
 1174    term_variables(H, Vars),
 1175    '$member'(V1, Vars),
 1176    '$member'(_=V2, VarNames),
 1177    V1 == V2,
 1178    !,
 1179    warnings_with_named_vars(T0, VarNames, T).
 1180warnings_with_named_vars([_|T0], VarNames, T) :-
 1181    warnings_with_named_vars(T0, VarNames, T).
 1182
 1183
 1184compiler_warnings([], _, _) --> [].
 1185compiler_warnings([H|T], Clause, Options) -->
 1186    (   compiler_warning(H, Clause, Options)
 1187    ->  []
 1188    ;   [ 'Unknown compiler warning: ~W'-[H,Options] ]
 1189    ),
 1190    (   {T==[]}
 1191    ->  []
 1192    ;   [nl]
 1193    ),
 1194    compiler_warnings(T, Clause, Options).
 1195
 1196compiler_warning(eq_vv(A,B), _Clause, Options) -->
 1197    (   { A == B }
 1198    ->  [ 'Test is always true: ~W'-[A==B, Options] ]
 1199    ;   [ 'Test is always false: ~W'-[A==B, Options] ]
 1200    ).
 1201compiler_warning(eq_singleton(A,B), _Clause, Options) -->
 1202    [ 'Test is always false: ~W'-[A==B, Options] ].
 1203compiler_warning(neq_vv(A,B), _Clause, Options) -->
 1204    (   { A \== B }
 1205    ->  [ 'Test is always true: ~W'-[A\==B, Options] ]
 1206    ;   [ 'Test is always false: ~W'-[A\==B, Options] ]
 1207    ).
 1208compiler_warning(neq_singleton(A,B), _Clause, Options) -->
 1209    [ 'Test is always true: ~W'-[A\==B, Options] ].
 1210compiler_warning(unify_singleton(A,B), _Clause, Options) -->
 1211    [ 'Unified variable is not used: ~W'-[A=B, Options] ].
 1212compiler_warning(always(Bool, Pred, Arg), _Clause, Options) -->
 1213    { Goal =.. [Pred,Arg] },
 1214    [ 'Test is always ~w: ~W'-[Bool, Goal, Options] ].
 1215compiler_warning(unbalanced_var(V), _Clause, Options) -->
 1216    [ 'Variable not introduced in all branches: ~W'-[V, Options] ].
 1217compiler_warning(branch_singleton(V), _Clause, Options) -->
 1218    [ 'Singleton variable in branch: ~W'-[V, Options] ].
 1219compiler_warning(negation_singleton(V), _Clause, Options) -->
 1220    [ 'Singleton variable in \\+: ~W'-[V, Options] ].
 1221compiler_warning(multiton(V), _Clause, Options) -->
 1222    [ 'Singleton-marked variable appears more than once: ~W'-[V, Options] ].
 1223
 1224print_goal_options(
 1225    [ quoted(true),
 1226      portray(true)
 1227    ]).
 1228
 1229
 1230                 /*******************************
 1231                 *      TOPLEVEL MESSAGES       *
 1232                 *******************************/
 1233
 1234prolog_message(version) -->
 1235    { current_prolog_flag(version_git, Version) },
 1236    !,
 1237    [ '~w'-[Version] ].
 1238prolog_message(version) -->
 1239    { current_prolog_flag(version_data, swi(Major,Minor,Patch,Options))
 1240    },
 1241    (   { memberchk(tag(Tag), Options) }
 1242    ->  [ '~w.~w.~w-~w'-[Major, Minor, Patch, Tag] ]
 1243    ;   [ '~w.~w.~w'-[Major, Minor, Patch] ]
 1244    ).
 1245prolog_message(address_bits) -->
 1246    { current_prolog_flag(address_bits, Bits)
 1247    },
 1248    !,
 1249    [ '~d bits, '-[Bits] ].
 1250prolog_message(threads) -->
 1251    { current_prolog_flag(threads, true)
 1252    },
 1253    !,
 1254    [ 'threaded, ' ].
 1255prolog_message(threads) -->
 1256    [].
 1257prolog_message(copyright) -->
 1258    [ 'SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software.', nl,
 1259      'Please run ?- license. for legal details.'
 1260    ].
 1261prolog_message(documentaton) -->
 1262    [ 'For online help and background, visit https://www.swi-prolog.org', nl,
 1263      'For built-in help, use ?- help(Topic). or ?- apropos(Word).'
 1264    ].
 1265prolog_message(about) -->
 1266    [ 'SWI-Prolog version (' ],
 1267    prolog_message(threads),
 1268    prolog_message(address_bits),
 1269    ['version ' ],
 1270    prolog_message(version),
 1271    [ ')', nl ],
 1272    prolog_message(copyright).
 1273prolog_message(halt) -->
 1274    [ 'halt' ].
 1275prolog_message(break(begin, Level)) -->
 1276    [ 'Break level ~d'-[Level] ].
 1277prolog_message(break(end, Level)) -->
 1278    [ 'Exit break level ~d'-[Level] ].
 1279prolog_message(var_query(_)) -->
 1280    [ '... 1,000,000 ............ 10,000,000 years later', nl, nl,
 1281      '~t~8|>> 42 << (last release gives the question)'
 1282    ].
 1283prolog_message(close_on_abort(Stream)) -->
 1284    [ 'Abort: closed stream ~p'-[Stream] ].
 1285prolog_message(cancel_halt(Reason)) -->
 1286    [ 'Halt cancelled: ~p'-[Reason] ].
 1287prolog_message(on_error(halt(Status))) -->
 1288    { statistics(errors, Errors),
 1289      statistics(warnings, Warnings)
 1290    },
 1291    [ 'Halting with status ~w due to ~D errors and ~D warnings'-
 1292      [Status, Errors, Warnings] ].
 1293
 1294prolog_message(query(QueryResult)) -->
 1295    query_result(QueryResult).
 1296
 1297query_result(no) -->            % failure
 1298    [ ansi(truth(false), 'false.', []) ],
 1299    extra_line.
 1300query_result(yes(true, [])) -->      % prompt_alternatives_on: groundness
 1301    !,
 1302    [ ansi(truth(true), 'true.', []) ],
 1303    extra_line.
 1304query_result(yes(Delays, Residuals)) -->
 1305    result([], Delays, Residuals),
 1306    extra_line.
 1307query_result(done) -->          % user typed <CR>
 1308    extra_line.
 1309query_result(yes(Bindings, Delays, Residuals)) -->
 1310    result(Bindings, Delays, Residuals),
 1311    prompt(yes, Bindings, Delays, Residuals).
 1312query_result(more(Bindings, Delays, Residuals)) -->
 1313    result(Bindings, Delays, Residuals),
 1314    prompt(more, Bindings, Delays, Residuals).
 1315query_result(help) -->
 1316    [ ansi(bold, '  Possible actions:', []), nl,
 1317      '  ; (n,r,space,TAB): redo              | t:         trace&redo'-[], nl,
 1318      '  *:                 show choicepoint  | c (a,RET): stop'-[], nl,
 1319      '  w:                 write             | p:         print'-[], nl,
 1320      '  b:                 break             | h (?):     help'-[],
 1321      nl, nl
 1322    ].
 1323query_result(action) -->
 1324    [ 'Action? '-[], flush ].
 1325query_result(confirm) -->
 1326    [ 'Please answer \'y\' or \'n\'? '-[], flush ].
 1327query_result(eof) -->
 1328    [ nl ].
 1329query_result(toplevel_open_line) -->
 1330    [].
 1331
 1332prompt(Answer, [], true, []-[]) -->
 1333    !,
 1334    prompt(Answer, empty).
 1335prompt(Answer, _, _, _) -->
 1336    !,
 1337    prompt(Answer, non_empty).
 1338
 1339prompt(yes, empty) -->
 1340    !,
 1341    [ ansi(truth(true), 'true.', []) ],
 1342    extra_line.
 1343prompt(yes, _) -->
 1344    !,
 1345    [ full_stop ],
 1346    extra_line.
 1347prompt(more, empty) -->
 1348    !,
 1349    [ ansi(truth(true), 'true ', []), flush ].
 1350prompt(more, _) -->
 1351    !,
 1352    [ ' '-[], flush ].
 1353
 1354result(Bindings, Delays, Residuals) -->
 1355    { current_prolog_flag(answer_write_options, Options0),
 1356      Options = [partial(true)|Options0],
 1357      GOptions = [priority(999)|Options0]
 1358    },
 1359    wfs_residual_program(Delays, GOptions),
 1360    bindings(Bindings, [priority(699)|Options]),
 1361    (   {Residuals == []-[]}
 1362    ->  bind_delays_sep(Bindings, Delays),
 1363        delays(Delays, GOptions)
 1364    ;   bind_res_sep(Bindings, Residuals),
 1365        residuals(Residuals, GOptions),
 1366        (   {Delays == true}
 1367        ->  []
 1368        ;   [','-[], nl],
 1369            delays(Delays, GOptions)
 1370        )
 1371    ).
 1372
 1373bindings([], _) -->
 1374    [].
 1375bindings([binding(Names,Skel,Subst)|T], Options) -->
 1376    { '$last'(Names, Name) },
 1377    var_names(Names), value(Name, Skel, Subst, Options),
 1378    (   { T \== [] }
 1379    ->  [ ','-[], nl ],
 1380        bindings(T, Options)
 1381    ;   []
 1382    ).
 1383
 1384var_names([Name]) -->
 1385    !,
 1386    [ '~w = '-[Name] ].
 1387var_names([Name1,Name2|T]) -->
 1388    !,
 1389    [ '~w = ~w, '-[Name1, Name2] ],
 1390    var_names([Name2|T]).
 1391
 1392
 1393value(Name, Skel, Subst, Options) -->
 1394    (   { var(Skel), Subst = [Skel=S] }
 1395    ->  { Skel = '$VAR'(Name) },
 1396        [ '~W'-[S, Options] ]
 1397    ;   [ '~W'-[Skel, Options] ],
 1398        substitution(Subst, Options)
 1399    ).
 1400
 1401substitution([], _) --> !.
 1402substitution([N=V|T], Options) -->
 1403    [ ', ', ansi(comment, '% where', []), nl,
 1404      '    ~w = ~W'-[N,V,Options] ],
 1405    substitutions(T, Options).
 1406
 1407substitutions([], _) --> [].
 1408substitutions([N=V|T], Options) -->
 1409    [ ','-[], nl, '    ~w = ~W'-[N,V,Options] ],
 1410    substitutions(T, Options).
 1411
 1412
 1413residuals(Normal-Hidden, Options) -->
 1414    residuals1(Normal, Options),
 1415    bind_res_sep(Normal, Hidden),
 1416    (   {Hidden == []}
 1417    ->  []
 1418    ;   [ansi(comment, '% with pending residual goals', []), nl]
 1419    ),
 1420    residuals1(Hidden, Options).
 1421
 1422residuals1([], _) -->
 1423    [].
 1424residuals1([G|Gs], Options) -->
 1425    (   { Gs \== [] }
 1426    ->  [ '~W,'-[G, Options], nl ],
 1427        residuals1(Gs, Options)
 1428    ;   [ '~W'-[G, Options] ]
 1429    ).
 1430
 1431wfs_residual_program(true, _Options) -->
 1432    !.
 1433wfs_residual_program(Goal, _Options) -->
 1434    { current_prolog_flag(toplevel_list_wfs_residual_program, true),
 1435      '$current_typein_module'(TypeIn),
 1436      (   current_predicate(delays_residual_program/2)
 1437      ->  true
 1438      ;   use_module(library(wfs), [delays_residual_program/2])
 1439      ),
 1440      delays_residual_program(TypeIn:Goal, TypeIn:Program),
 1441      Program \== []
 1442    },
 1443    !,
 1444    [ ansi(comment, '% WFS residual program', []), nl ],
 1445    [ ansi(wfs(residual_program), '~@', ['$messages':list_clauses(Program)]) ].
 1446wfs_residual_program(_, _) --> [].
 1447
 1448delays(true, _Options) -->
 1449    !.
 1450delays(Goal, Options) -->
 1451    { current_prolog_flag(toplevel_list_wfs_residual_program, true)
 1452    },
 1453    !,
 1454    [ ansi(truth(undefined), '~W', [Goal, Options]) ].
 1455delays(_, _Options) -->
 1456    [ ansi(truth(undefined), undefined, []) ].
 1457
 1458:- public list_clauses/1. 1459
 1460list_clauses([]).
 1461list_clauses([H|T]) :-
 1462    (   system_undefined(H)
 1463    ->  true
 1464    ;   portray_clause(user_output, H, [indent(4)])
 1465    ),
 1466    list_clauses(T).
 1467
 1468system_undefined((undefined :- tnot(undefined))).
 1469system_undefined((answer_count_restraint :- tnot(answer_count_restraint))).
 1470system_undefined((radial_restraint :- tnot(radial_restraint))).
 1471
 1472bind_res_sep(_, []) --> !.
 1473bind_res_sep(_, []-[]) --> !.
 1474bind_res_sep([], _) --> !.
 1475bind_res_sep(_, _) --> [','-[], nl].
 1476
 1477bind_delays_sep([], _) --> !.
 1478bind_delays_sep(_, true) --> !.
 1479bind_delays_sep(_, _) --> [','-[], nl].
 1480
 1481extra_line -->
 1482    { current_prolog_flag(toplevel_extra_white_line, true) },
 1483    !,
 1484    ['~N'-[]].
 1485extra_line -->
 1486    [].
 1487
 1488prolog_message(if_tty(Message)) -->
 1489    (   {current_prolog_flag(tty_control, true)}
 1490    ->  [ at_same_line | Message ]
 1491    ;   []
 1492    ).
 1493prolog_message(halt(Reason)) -->
 1494    [ '~w: halt'-[Reason] ].
 1495prolog_message(no_action(Char)) -->
 1496    [ 'Unknown action: ~c (h for help)'-[Char], nl ].
 1497
 1498prolog_message(history(help(Show, Help))) -->
 1499    [ 'History Commands:', nl,
 1500      '    !!.              Repeat last query', nl,
 1501      '    !nr.             Repeat query numbered <nr>', nl,
 1502      '    !str.            Repeat last query starting with <str>', nl,
 1503      '    !?str.           Repeat last query holding <str>', nl,
 1504      '    ^old^new.        Substitute <old> into <new> of last query', nl,
 1505      '    !nr^old^new.     Substitute in query numbered <nr>', nl,
 1506      '    !str^old^new.    Substitute in query starting with <str>', nl,
 1507      '    !?str^old^new.   Substitute in query holding <str>', nl,
 1508      '    ~w.~21|Show history list'-[Show], nl,
 1509      '    ~w.~21|Show this list'-[Help], nl, nl
 1510    ].
 1511prolog_message(history(no_event)) -->
 1512    [ '! No such event' ].
 1513prolog_message(history(bad_substitution)) -->
 1514    [ '! Bad substitution' ].
 1515prolog_message(history(expanded(Event))) -->
 1516    [ '~w.'-[Event] ].
 1517prolog_message(history(history(Events))) -->
 1518    history_events(Events).
 1519
 1520history_events([]) -->
 1521    [].
 1522history_events([Nr/Event|T]) -->
 1523    [ '~t~w   ~8|~W~W'-[ Nr,
 1524                         Event, [partial(true)],
 1525                         '.', [partial(true)]
 1526                       ],
 1527      nl
 1528    ],
 1529    history_events(T).
 user_version_messages(+Terms)//
Helper for the welcome message to print information registered using version/1.
 1537user_version_messages([]) --> [].
 1538user_version_messages([H|T]) -->
 1539    user_version_message(H),
 1540    user_version_messages(T).
 user_version_message(+Term)
 1544user_version_message(Term) -->
 1545    translate_message(Term), !, [nl].
 1546user_version_message(Atom) -->
 1547    [ '~w'-[Atom], nl ].
 1548
 1549
 1550                 /*******************************
 1551                 *       DEBUGGER MESSAGES      *
 1552                 *******************************/
 1553
 1554prolog_message(spy(Head)) -->
 1555    { goal_to_predicate_indicator(Head, Pred)
 1556    },
 1557    [ 'Spy point on ~p'-[Pred] ].
 1558prolog_message(nospy(Head)) -->
 1559    { goal_to_predicate_indicator(Head, Pred)
 1560    },
 1561    [ 'Spy point removed from ~p'-[Pred] ].
 1562prolog_message(trace_mode(OnOff)) -->
 1563    [ 'Trace mode switched to ~w'-[OnOff] ].
 1564prolog_message(debug_mode(OnOff)) -->
 1565    [ 'Debug mode switched to ~w'-[OnOff] ].
 1566prolog_message(debugging(OnOff)) -->
 1567    [ 'Debug mode is ~w'-[OnOff] ].
 1568prolog_message(spying([])) -->
 1569    !,
 1570    [ 'No spy points' ].
 1571prolog_message(spying(Heads)) -->
 1572    [ 'Spy points (see spy/1) on:', nl ],
 1573    predicate_list(Heads).
 1574prolog_message(trace(Head, [])) -->
 1575    !,
 1576    { goal_to_predicate_indicator(Head, Pred)
 1577    },
 1578    [ '        ~p: Not tracing'-[Pred], nl].
 1579prolog_message(trace(Head, Ports)) -->
 1580    { goal_to_predicate_indicator(Head, Pred)
 1581    },
 1582    [ '        ~p: ~w'-[Pred, Ports], nl].
 1583prolog_message(tracing([])) -->
 1584    !,
 1585    [ 'No traced predicates (see trace/1)' ].
 1586prolog_message(tracing(Heads)) -->
 1587    [ 'Trace points (see trace/1) on:', nl ],
 1588    tracing_list(Heads).
 1589
 1590predicate_list([]) -->                  % TBD: Share with dwim, etc.
 1591    [].
 1592predicate_list([H|T]) -->
 1593    { goal_to_predicate_indicator(H, Pred)
 1594    },
 1595    [ '        ~p'-[Pred], nl],
 1596    predicate_list(T).
 1597
 1598tracing_list([]) -->
 1599    [].
 1600tracing_list([trace(Head, Ports)|T]) -->
 1601    translate_message(trace(Head, Ports)),
 1602    tracing_list(T).
 1603
 1604prolog_message(frame(Frame, backtrace, _PC)) -->
 1605    !,
 1606    { prolog_frame_attribute(Frame, level, Level)
 1607    },
 1608    [ ansi(frame(level), '~t[~D] ~10|', [Level]) ],
 1609    frame_context(Frame),
 1610    frame_goal(Frame).
 1611prolog_message(frame(Frame, choice, PC)) -->
 1612    !,
 1613    prolog_message(frame(Frame, backtrace, PC)).
 1614prolog_message(frame(_, cut_call, _)) --> !, [].
 1615prolog_message(frame(Goal, trace(Port))) -->
 1616    !,
 1617    thread_context,
 1618    [ ' T ' ],
 1619    port(Port),
 1620    goal(Goal).
 1621prolog_message(frame(Goal, trace(Port, Id))) -->
 1622    !,
 1623    thread_context,
 1624    [ ' T ' ],
 1625    port(Port, Id),
 1626    goal(Goal).
 1627prolog_message(frame(Frame, Port, _PC)) -->
 1628    frame_flags(Frame),
 1629    port(Port),
 1630    frame_level(Frame),
 1631    frame_context(Frame),
 1632    frame_depth_limit(Port, Frame),
 1633    frame_goal(Frame),
 1634    [ flush ].
 1635
 1636frame_goal(Frame) -->
 1637    { prolog_frame_attribute(Frame, goal, Goal)
 1638    },
 1639    goal(Goal).
 1640
 1641goal(Goal0) -->
 1642    { clean_goal(Goal0, Goal),
 1643      current_prolog_flag(debugger_write_options, Options)
 1644    },
 1645    [ '~W'-[Goal, Options] ].
 1646
 1647frame_level(Frame) -->
 1648    { prolog_frame_attribute(Frame, level, Level)
 1649    },
 1650    [ '(~D) '-[Level] ].
 1651
 1652frame_context(Frame) -->
 1653    (   { current_prolog_flag(debugger_show_context, true),
 1654          prolog_frame_attribute(Frame, context_module, Context)
 1655        }
 1656    ->  [ '[~w] '-[Context] ]
 1657    ;   []
 1658    ).
 1659
 1660frame_depth_limit(fail, Frame) -->
 1661    { prolog_frame_attribute(Frame, depth_limit_exceeded, true)
 1662    },
 1663    !,
 1664    [ '[depth-limit exceeded] ' ].
 1665frame_depth_limit(_, _) -->
 1666    [].
 1667
 1668frame_flags(Frame) -->
 1669    { prolog_frame_attribute(Frame, goal, Goal),
 1670      (   predicate_property(Goal, transparent)
 1671      ->  T = '^'
 1672      ;   T = ' '
 1673      ),
 1674      (   predicate_property(Goal, spying)
 1675      ->  S = '*'
 1676      ;   S = ' '
 1677      )
 1678    },
 1679    [ '~w~w '-[T, S] ].
 1680
 1681% trace/1,2 context handling
 1682port(Port, _Id-Level) -->
 1683    [ '[~d] '-Level ],
 1684    port(Port).
 1685
 1686port(Port) -->
 1687    { port_name(Port, Name)
 1688    },
 1689    !,
 1690    [ ansi(port(Port), '~w: ', [Name]) ].
 1691
 1692port_name(call,      'Call').
 1693port_name(exit,      'Exit').
 1694port_name(fail,      'Fail').
 1695port_name(redo,      'Redo').
 1696port_name(unify,     'Unify').
 1697port_name(exception, 'Exception').
 1698
 1699clean_goal(M:Goal, Goal) :-
 1700    hidden_module(M),
 1701    !.
 1702clean_goal(M:Goal, Goal) :-
 1703    predicate_property(M:Goal, built_in),
 1704    !.
 1705clean_goal(Goal, Goal).
 1706
 1707
 1708                 /*******************************
 1709                 *        COMPATIBILITY         *
 1710                 *******************************/
 1711
 1712prolog_message(compatibility(renamed(Old, New))) -->
 1713    [ 'The predicate ~p has been renamed to ~p.'-[Old, New], nl,
 1714      'Please update your sources for compatibility with future versions.'
 1715    ].
 1716
 1717
 1718                 /*******************************
 1719                 *            THREADS           *
 1720                 *******************************/
 1721
 1722prolog_message(abnormal_thread_completion(Goal, exception(Ex))) -->
 1723    !,
 1724    [ 'Thread running "~p" died on exception: '-[Goal] ],
 1725    translate_message(Ex).
 1726prolog_message(abnormal_thread_completion(Goal, fail)) -->
 1727    [ 'Thread running "~p" died due to failure'-[Goal] ].
 1728prolog_message(threads_not_died(Running)) -->
 1729    [ 'The following threads wouldn\'t die: ~p'-[Running] ].
 1730
 1731
 1732                 /*******************************
 1733                 *             PACKS            *
 1734                 *******************************/
 1735
 1736prolog_message(pack(attached(Pack, BaseDir))) -->
 1737    [ 'Attached package ~w at ~q'-[Pack, BaseDir] ].
 1738prolog_message(pack(duplicate(Entry, OldDir, Dir))) -->
 1739    [ 'Package ~w already attached at ~q.'-[Entry,OldDir], nl,
 1740      '\tIgnoring version from ~q'- [Dir]
 1741    ].
 1742prolog_message(pack(no_arch(Entry, Arch))) -->
 1743    [ 'Package ~w: no binary for architecture ~w'-[Entry, Arch] ].
 1744
 1745                 /*******************************
 1746                 *             MISC             *
 1747                 *******************************/
 1748
 1749prolog_message(null_byte_in_path(Component)) -->
 1750    [ '0-byte in PATH component: ~p (skipped directory)'-[Component] ].
 1751prolog_message(invalid_tmp_dir(Dir, Reason)) -->
 1752    [ 'Cannot use ~p as temporary file directory: ~w'-[Dir, Reason] ].
 1753prolog_message(ambiguous_stream_pair(Pair)) -->
 1754    [ 'Ambiguous operation on stream pair ~p'-[Pair] ].
 1755prolog_message(backcomp(init_file_moved(FoundFile))) -->
 1756    { absolute_file_name(app_config('init.pl'), InitFile,
 1757                         [ file_errors(fail)
 1758                         ])
 1759    },
 1760    [ 'The location of the config file has moved'-[], nl,
 1761      '  from "~w"'-[FoundFile], nl,
 1762      '  to   "~w"'-[InitFile], nl,
 1763      '  See https://www.swi-prolog.org/modified/config-files.html'-[]
 1764    ].
 1765
 1766		 /*******************************
 1767		 *          DEPRECATED		*
 1768		 *******************************/
 1769
 1770deprecated(set_prolog_stack(_Stack,limit)) -->
 1771    [ 'set_prolog_stack/2: limit(Size) sets the combined limit.'-[], nl,
 1772      'See https://www.swi-prolog.org/changes/stack-limit.html'
 1773    ].
 1774
 1775		 /*******************************
 1776		 *           TRIPWIRES		*
 1777		 *******************************/
 1778
 1779tripwire_message(Wire, Context) -->
 1780    [ 'Trapped tripwire ~w for '-[Wire] ],
 1781    tripwire_context(Wire, Context).
 1782
 1783tripwire_context(_, ATrie) -->
 1784    { '$is_answer_trie'(ATrie, _),
 1785      !,
 1786      '$tabling':atrie_goal(ATrie, QGoal),
 1787      user_predicate_indicator(QGoal, Goal)
 1788    },
 1789    [ '~p'-[Goal] ].
 1790tripwire_context(_, Ctx) -->
 1791    [ '~p'-[Ctx] ].
 1792
 1793
 1794		 /*******************************
 1795		 *     INTERNATIONALIZATION	*
 1796		 *******************************/
 1797
 1798:- create_prolog_flag(message_language, default, []).
 message_lang(-Lang) is multi
True when Lang is a language id preferred for messages. Starts with the most specific language (e.g., nl_BE) and ends with en.
 1805message_lang(Lang) :-
 1806    current_message_lang(Lang0),
 1807    (   Lang0 == en
 1808    ->  Lang = en
 1809    ;   sub_atom(Lang0, 0, _, _, en_)
 1810    ->  longest_id(Lang0, Lang)
 1811    ;   (   longest_id(Lang0, Lang)
 1812        ;   Lang = en
 1813        )
 1814    ).
 1815
 1816longest_id(Lang, Id) :-
 1817    split_string(Lang, "_-", "", [H|Components]),
 1818    longest_prefix(Components, Taken),
 1819    atomic_list_concat([H|Taken], '_', Id).
 1820
 1821longest_prefix([H|T0], [H|T]) :-
 1822    longest_prefix(T0, T).
 1823longest_prefix(_, []).
 current_message_lang(-Lang) is det
Get the current language for messages.
 1829current_message_lang(Lang) :-
 1830    (   current_prolog_flag(message_language, Lang0),
 1831        Lang0 \== default
 1832    ->  Lang = Lang0
 1833    ;   os_user_lang(Lang0)
 1834    ->  clean_encoding(Lang0, Lang1),
 1835        set_prolog_flag(message_language, Lang1),
 1836        Lang = Lang1
 1837    ;   Lang = en
 1838    ).
 1839
 1840os_user_lang(Lang) :-
 1841    current_prolog_flag(windows, true),
 1842    win_get_user_preferred_ui_languages(name, [Lang|_]).
 1843os_user_lang(Lang) :-
 1844    catch(setlocale(messages, _, ''), _, fail),
 1845    setlocale(messages, Lang, Lang).
 1846os_user_lang(Lang) :-
 1847    getenv('LANG', Lang).
 1848
 1849
 1850clean_encoding(Lang0, Lang) :-
 1851    (   sub_atom(Lang0, A, _, _, '.')
 1852    ->  sub_atom(Lang0, 0, A, _, Lang)
 1853    ;   Lang = Lang0
 1854    ).
 1855
 1856		 /*******************************
 1857		 *          PRIMITIVES		*
 1858		 *******************************/
 1859
 1860code(Term) -->
 1861    code('~p', Term).
 1862
 1863code(Format, Term) -->
 1864    [ ansi(code, Format, [Term]) ].
 1865
 1866
 1867		 /*******************************
 1868		 *        DEFAULT THEME		*
 1869		 *******************************/
 1870
 1871:- public default_theme/2. 1872
 1873default_theme(var,                    [fg(red)]).
 1874default_theme(code,                   [fg(blue)]).
 1875default_theme(comment,                [fg(green)]).
 1876default_theme(warning,                [fg(red)]).
 1877default_theme(error,                  [bold, fg(red)]).
 1878default_theme(truth(false),           [bold, fg(red)]).
 1879default_theme(truth(true),            [bold]).
 1880default_theme(truth(undefined),       [bold, fg(cyan)]).
 1881default_theme(wfs(residual_program),  [fg(cyan)]).
 1882default_theme(frame(level),           [bold]).
 1883default_theme(port(call),             [bold, fg(green)]).
 1884default_theme(port(exit),             [bold, fg(green)]).
 1885default_theme(port(fail),             [bold, fg(red)]).
 1886default_theme(port(redo),             [bold, fg(yellow)]).
 1887default_theme(port(unify),            [bold, fg(blue)]).
 1888default_theme(port(exception),        [bold, fg(magenta)]).
 1889default_theme(message(informational), [fg(green)]).
 1890default_theme(message(information),   [fg(green)]).
 1891default_theme(message(debug(_)),      [fg(blue)]).
 1892default_theme(message(Level),         Attrs) :-
 1893    nonvar(Level),
 1894    default_theme(Level, Attrs).
 1895
 1896
 1897                 /*******************************
 1898                 *      PRINTING MESSAGES       *
 1899                 *******************************/
 1900
 1901:- multifile
 1902    user:message_hook/3,
 1903    prolog:message_prefix_hook/2. 1904:- dynamic
 1905    user:message_hook/3,
 1906    prolog:message_prefix_hook/2. 1907:- thread_local
 1908    user:thread_message_hook/3. 1909:- '$hide'((push_msg/1,pop_msg/0)).
 print_message(+Kind, +Term)
Print an error message using a term as generated by the exception system.
 1916print_message(Level, Term) :-
 1917    setup_call_cleanup(
 1918        push_msg(Term),
 1919        print_message_guarded(Level, Term),
 1920        pop_msg),
 1921    !.
 1922print_message(Level, Term) :-
 1923    (   Level \== silent
 1924    ->  format(user_error, 'Recursive ~w message: ~q~n', [Level, Term])
 1925    ;   true
 1926    ).
 1927
 1928push_msg(Term) :-
 1929    nb_current('$inprint_message', Messages),
 1930    !,
 1931    \+ ( '$member'(Msg, Messages),
 1932         Msg =@= Term
 1933       ),
 1934    b_setval('$inprint_message', [Term|Messages]).
 1935push_msg(Term) :-
 1936    b_setval('$inprint_message', [Term]).
 1937
 1938pop_msg :-
 1939    (   nb_current('$inprint_message', [_|Messages]),
 1940        Messages \== []
 1941    ->  b_setval('$inprint_message', Messages)
 1942    ;   nb_delete('$inprint_message'),              % delete history
 1943        b_setval('$inprint_message', [])
 1944    ).
 1945
 1946print_message_guarded(Level, Term) :-
 1947    (   must_print(Level, Term)
 1948    ->  (   translate_message(Term, Lines, [])
 1949        ->  (   nonvar(Term),
 1950                (   notrace(user:thread_message_hook(Term, Level, Lines))
 1951                ->  true
 1952                ;   notrace(user:message_hook(Term, Level, Lines))
 1953                )
 1954            ->  true
 1955            ;   '$inc_message_count'(Level),
 1956                print_system_message(Term, Level, Lines),
 1957                maybe_halt_on_error(Level)
 1958            )
 1959        )
 1960    ;   true
 1961    ).
 1962
 1963maybe_halt_on_error(error) :-
 1964    current_prolog_flag(on_error, halt),
 1965    !,
 1966    halt(1).
 1967maybe_halt_on_error(warning) :-
 1968    current_prolog_flag(on_warning, halt),
 1969    !,
 1970    halt(1).
 1971maybe_halt_on_error(_).
 print_system_message(+Term, +Kind, +Lines)
Print the message if the user did not intecept the message. The first is used for errors and warnings that can be related to source-location. Note that syntax errors have their own source-location and should therefore not be handled this way.
 1981print_system_message(_, silent, _) :- !.
 1982print_system_message(_, informational, _) :-
 1983    current_prolog_flag(verbose, silent),
 1984    !.
 1985print_system_message(_, banner, _) :-
 1986    current_prolog_flag(verbose, silent),
 1987    !.
 1988print_system_message(_, _, []) :- !.
 1989print_system_message(Term, Kind, Lines) :-
 1990    catch(flush_output(user_output), _, true),      % may not exist
 1991    source_location(File, Line),
 1992    Term \= error(syntax_error(_), _),
 1993    msg_property(Kind, location_prefix(File:Line, LocPrefix, LinePrefix)),
 1994    !,
 1995    to_list(LocPrefix, LocPrefixL),
 1996    insert_prefix(Lines, LinePrefix, Ctx, PrefixLines),
 1997    '$append'([ [begin(Kind, Ctx)],
 1998                LocPrefixL,
 1999                [nl],
 2000                PrefixLines,
 2001                [end(Ctx)]
 2002              ],
 2003              AllLines),
 2004    msg_property(Kind, stream(Stream)),
 2005    ignore(stream_property(Stream, position(Pos))),
 2006    print_message_lines(Stream, AllLines),
 2007    (   \+ stream_property(Stream, position(Pos)),
 2008        msg_property(Kind, wait(Wait)),
 2009        Wait > 0
 2010    ->  sleep(Wait)
 2011    ;   true
 2012    ).
 2013print_system_message(_, Kind, Lines) :-
 2014    msg_property(Kind, stream(Stream)),
 2015    print_message_lines(Stream, kind(Kind), Lines).
 2016
 2017to_list(ListIn, List) :-
 2018    is_list(ListIn),
 2019    !,
 2020    List = ListIn.
 2021to_list(NonList, [NonList]).
 2022
 2023:- multifile
 2024    user:message_property/2. 2025
 2026msg_property(Kind, Property) :-
 2027    notrace(user:message_property(Kind, Property)),
 2028    !.
 2029msg_property(Kind, prefix(Prefix)) :-
 2030    msg_prefix(Kind, Prefix),
 2031    !.
 2032msg_property(_, prefix('~N')) :- !.
 2033msg_property(query, stream(user_output)) :- !.
 2034msg_property(_, stream(user_error)) :- !.
 2035msg_property(error, tag('ERROR')).
 2036msg_property(warning, tag('Warning')).
 2037msg_property(Level,
 2038             location_prefix(File:Line,
 2039                             ['~N~w: '-[Tag], url(File:Line), ':'],
 2040                             '~N~w:    '-[Tag])) :-
 2041    include_msg_location(Level),
 2042    msg_property(Level, tag(Tag)).
 2043msg_property(error,   wait(0.1)) :- !.
 2044
 2045include_msg_location(warning).
 2046include_msg_location(error).
 2047
 2048msg_prefix(debug(_), Prefix) :-
 2049    msg_context('~N% ', Prefix).
 2050msg_prefix(Level, Prefix) :-
 2051    msg_property(Level, tag(Tag)),
 2052    atomics_to_string(['~N', Tag, ': '], Prefix0),
 2053    msg_context(Prefix0, Prefix).
 2054msg_prefix(informational, '~N% ').
 2055msg_prefix(information,   '~N% ').
 msg_context(+Prefix0, -Prefix) is det
Add contextual information to a message. This uses the Prolog flag message_context. Recognised context terms are:

In addition, the hook message_prefix_hook/2 is called that allows for additional context information.

 2069msg_context(Prefix0, Prefix) :-
 2070    current_prolog_flag(message_context, Context),
 2071    is_list(Context),
 2072    !,
 2073    add_message_context(Context, Prefix0, Prefix).
 2074msg_context(Prefix, Prefix).
 2075
 2076add_message_context([], Prefix, Prefix).
 2077add_message_context([H|T], Prefix0, Prefix) :-
 2078    (   add_message_context1(H, Prefix0, Prefix1)
 2079    ->  true
 2080    ;   Prefix1 = Prefix0
 2081    ),
 2082    add_message_context(T, Prefix1, Prefix).
 2083
 2084add_message_context1(Context, Prefix0, Prefix) :-
 2085    prolog:message_prefix_hook(Context, Extra),
 2086    atomics_to_string([Prefix0, Extra, ' '], Prefix).
 2087add_message_context1(time, Prefix0, Prefix) :-
 2088    get_time(Now),
 2089    format_time(string(S), '%T.%3f ', Now),
 2090    string_concat(Prefix0, S, Prefix).
 2091add_message_context1(time(Format), Prefix0, Prefix) :-
 2092    get_time(Now),
 2093    format_time(string(S), Format, Now),
 2094    atomics_to_string([Prefix0, S, ' '], Prefix).
 2095add_message_context1(thread, Prefix0, Prefix) :-
 2096    thread_self(Id0),
 2097    Id0 \== main,
 2098    !,
 2099    (   atom(Id0)
 2100    ->  Id = Id0
 2101    ;   thread_property(Id0, id(Id))
 2102    ),
 2103    format(string(Prefix), '~w[Thread ~w] ', [Prefix0, Id]).
 print_message_lines(+Stream, +PrefixOrKind, +Lines)
Quintus compatibility predicate to print message lines using a prefix.
 2110print_message_lines(Stream, kind(Kind), Lines) :-
 2111    !,
 2112    msg_property(Kind, prefix(Prefix)),
 2113    insert_prefix(Lines, Prefix, Ctx, PrefixLines),
 2114    '$append'([ begin(Kind, Ctx)
 2115              | PrefixLines
 2116              ],
 2117              [ end(Ctx)
 2118              ],
 2119              AllLines),
 2120    print_message_lines(Stream, AllLines).
 2121print_message_lines(Stream, Prefix, Lines) :-
 2122    insert_prefix(Lines, Prefix, _, PrefixLines),
 2123    print_message_lines(Stream, PrefixLines).
 insert_prefix(+Lines, +Prefix, +Ctx, -PrefixedLines)
 2127insert_prefix([at_same_line|Lines0], Prefix, Ctx, Lines) :-
 2128    !,
 2129    prefix_nl(Lines0, Prefix, Ctx, Lines).
 2130insert_prefix(Lines0, Prefix, Ctx, [prefix(Prefix)|Lines]) :-
 2131    prefix_nl(Lines0, Prefix, Ctx, Lines).
 2132
 2133prefix_nl([], _, _, [nl]).
 2134prefix_nl([nl], _, _, [nl]) :- !.
 2135prefix_nl([flush], _, _, [flush]) :- !.
 2136prefix_nl([nl|T0], Prefix, Ctx, [nl, prefix(Prefix)|T]) :-
 2137    !,
 2138    prefix_nl(T0, Prefix, Ctx, T).
 2139prefix_nl([ansi(Attrs,Fmt,Args)|T0], Prefix, Ctx,
 2140          [ansi(Attrs,Fmt,Args,Ctx)|T]) :-
 2141    !,
 2142    prefix_nl(T0, Prefix, Ctx, T).
 2143prefix_nl([H|T0], Prefix, Ctx, [H|T]) :-
 2144    prefix_nl(T0, Prefix, Ctx, T).
 print_message_lines(+Stream, +Lines)
 2148print_message_lines(Stream, Lines) :-
 2149    with_output_to(
 2150        Stream,
 2151        notrace(print_message_lines_guarded(current_output, Lines))).
 2152
 2153print_message_lines_guarded(_, []) :- !.
 2154print_message_lines_guarded(S, [H|T]) :-
 2155    line_element(S, H),
 2156    print_message_lines_guarded(S, T).
 2157
 2158line_element(S, E) :-
 2159    prolog:message_line_element(S, E),
 2160    !.
 2161line_element(S, full_stop) :-
 2162    !,
 2163    '$put_token'(S, '.').           % insert space if needed.
 2164line_element(S, nl) :-
 2165    !,
 2166    nl(S).
 2167line_element(S, prefix(Fmt-Args)) :-
 2168    !,
 2169    safe_format(S, Fmt, Args).
 2170line_element(S, prefix(Fmt)) :-
 2171    !,
 2172    safe_format(S, Fmt, []).
 2173line_element(S, flush) :-
 2174    !,
 2175    flush_output(S).
 2176line_element(S, Fmt-Args) :-
 2177    !,
 2178    safe_format(S, Fmt, Args).
 2179line_element(S, ansi(_, Fmt, Args)) :-
 2180    !,
 2181    safe_format(S, Fmt, Args).
 2182line_element(S, ansi(_, Fmt, Args, _Ctx)) :-
 2183    !,
 2184    safe_format(S, Fmt, Args).
 2185line_element(S, url(URL)) :-
 2186    !,
 2187    print_link(S, URL).
 2188line_element(S, url(_URL, Fmt-Args)) :-
 2189    !,
 2190    safe_format(S, Fmt, Args).
 2191line_element(S, url(_URL, Fmt)) :-
 2192    !,
 2193    safe_format(S, Fmt, []).
 2194line_element(_, begin(_Level, _Ctx)) :- !.
 2195line_element(_, end(_Ctx)) :- !.
 2196line_element(S, Fmt) :-
 2197    safe_format(S, Fmt, []).
 2198
 2199print_link(S, File:Line:Column) :-
 2200    !,
 2201    safe_format(S, '~w:~d:~d', [File, Line, Column]).
 2202print_link(S, File:Line) :-
 2203    !,
 2204    safe_format(S, '~w:~d', [File, Line]).
 2205print_link(S, File) :-
 2206    safe_format(S, '~w', [File]).
 safe_format(+Stream, +Format, +Args) is det
 2210safe_format(S, Fmt, Args) :-
 2211    E = error(_,_),
 2212    catch(format(S,Fmt,Args), E,
 2213          format_failed(S,Fmt,Args,E)).
 2214
 2215format_failed(S, _Fmt, _Args, E) :-
 2216    E = error(io_error(_,S),_),
 2217    !,
 2218    throw(E).
 2219format_failed(S, Fmt, Args, error(E,_)) :-
 2220    format(S, '~N    [[ EXCEPTION while printing message ~q~n\c
 2221                        ~7|with arguments ~W:~n\c
 2222                        ~7|raised: ~W~n~4|]]~n',
 2223           [ Fmt,
 2224             Args, [quoted(true), max_depth(10)],
 2225             E, [quoted(true), max_depth(10)]
 2226           ]).
 message_to_string(+Term, -String)
Translate an error term into a string
 2232message_to_string(Term, Str) :-
 2233    translate_message(Term, Actions, []),
 2234    !,
 2235    actions_to_format(Actions, Fmt, Args),
 2236    format(string(Str), Fmt, Args).
 2237
 2238actions_to_format([], '', []) :- !.
 2239actions_to_format([nl], '', []) :- !.
 2240actions_to_format([Term, nl], Fmt, Args) :-
 2241    !,
 2242    actions_to_format([Term], Fmt, Args).
 2243actions_to_format([nl|T], Fmt, Args) :-
 2244    !,
 2245    actions_to_format(T, Fmt0, Args),
 2246    atom_concat('~n', Fmt0, Fmt).
 2247actions_to_format([ansi(_Attrs, Fmt0, Args0)|Tail], Fmt, Args) :-
 2248    !,
 2249    actions_to_format(Tail, Fmt1, Args1),
 2250    atom_concat(Fmt0, Fmt1, Fmt),
 2251    append_args(Args0, Args1, Args).
 2252actions_to_format([url(Pos)|Tail], Fmt, Args) :-
 2253    !,
 2254    actions_to_format(Tail, Fmt1, Args1),
 2255    url_actions_to_format(url(Pos), Fmt1, Args1, Fmt, Args).
 2256actions_to_format([url(URL, Label)|Tail], Fmt, Args) :-
 2257    !,
 2258    actions_to_format(Tail, Fmt1, Args1),
 2259    url_actions_to_format(url(URL, Label), Fmt1, Args1, Fmt, Args).
 2260actions_to_format([Fmt0-Args0|Tail], Fmt, Args) :-
 2261    !,
 2262    actions_to_format(Tail, Fmt1, Args1),
 2263    atom_concat(Fmt0, Fmt1, Fmt),
 2264    append_args(Args0, Args1, Args).
 2265actions_to_format([Skip|T], Fmt, Args) :-
 2266    action_skip(Skip),
 2267    !,
 2268    actions_to_format(T, Fmt, Args).
 2269actions_to_format([Term|Tail], Fmt, Args) :-
 2270    atomic(Term),
 2271    !,
 2272    actions_to_format(Tail, Fmt1, Args),
 2273    atom_concat(Term, Fmt1, Fmt).
 2274actions_to_format([Term|Tail], Fmt, Args) :-
 2275    actions_to_format(Tail, Fmt1, Args1),
 2276    atom_concat('~w', Fmt1, Fmt),
 2277    append_args([Term], Args1, Args).
 2278
 2279action_skip(at_same_line).
 2280action_skip(flush).
 2281action_skip(begin(_Level, _Ctx)).
 2282action_skip(end(_Ctx)).
 2283
 2284url_actions_to_format(url(File:Line:Column), Fmt1, Args1, Fmt, Args) :-
 2285    !,
 2286    atom_concat('~w:~d:~d', Fmt1, Fmt),
 2287    append_args([File,Line,Column], Args1, Args).
 2288url_actions_to_format(url(File:Line), Fmt1, Args1, Fmt, Args) :-
 2289    !,
 2290    atom_concat('~w:~d', Fmt1, Fmt),
 2291    append_args([File,Line], Args1, Args).
 2292url_actions_to_format(url(File), Fmt1, Args1, Fmt, Args) :-
 2293    !,
 2294    atom_concat('~w', Fmt1, Fmt),
 2295    append_args([File], Args1, Args).
 2296url_actions_to_format(url(_URL, Label), Fmt1, Args1, Fmt, Args) :-
 2297    !,
 2298    atom_concat('~w', Fmt1, Fmt),
 2299    append_args([Label], Args1, Args).
 2300
 2301
 2302append_args(M:Args0, Args1, M:Args) :-
 2303    !,
 2304    strip_module(Args1, _, A1),
 2305    to_list(Args0, Args01),
 2306    '$append'(Args01, A1, Args).
 2307append_args(Args0, Args1, Args) :-
 2308    strip_module(Args1, _, A1),
 2309    to_list(Args0, Args01),
 2310    '$append'(Args01, A1, Args).
 2311
 2312                 /*******************************
 2313                 *    MESSAGES TO PRINT ONCE    *
 2314                 *******************************/
 2315
 2316:- dynamic
 2317    printed/2.
 print_once(Message, Level)
True for messages that must be printed only once.
 2323print_once(compatibility(_), _).
 2324print_once(null_byte_in_path(_), _).
 2325print_once(deprecated(_), _).
 must_print(+Level, +Message)
True if the message must be printed.
 2331must_print(Level, Message) :-
 2332    nonvar(Message),
 2333    print_once(Message, Level),
 2334    !,
 2335    \+ printed(Message, Level),
 2336    assert(printed(Message, Level)).
 2337must_print(_, _)