87 lines
2.1 KiB
Prolog
87 lines
2.1 KiB
Prolog
:- module(dialect,
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[
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exists_source/1,
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source_exports/2
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]).
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prolog:'$expects_dialect'(yap) :- !,
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eraseall('$dialect'),
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recorda('$dialect',yap,_).
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prolog:'$expects_dialect'(Dialect) :-
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check_dialect(Dialect),
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eraseall('$dialect'),
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load_files(library(dialect/Dialect),[silent(true),if(not_loaded)]),
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( current_predicate(Dialect:setup_dialect/0)
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-> Dialect:setup_dialect
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; true
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),
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recorda('$dialect',Dialect,_).
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check_dialect(Dialect) :-
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var(Dialect),!,
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'$do_error'(instantiation_error,(:- dialect(Dialect))).
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check_dialect(Dialect) :-
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\+ atom(Dialect),!,
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'$do_error'(type_error(Dialect),(:- dialect(Dialect))).
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check_dialect(Dialect) :-
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exists_source(library(dialect/Dialect)), !.
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check_dialect(Dialect) :-
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'$do_error'(domain_error(dialect,Dialect),(:- dialect(Dialect))).
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%% exists_source(+Source) is semidet.
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%
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% True if Source (a term valid for load_files/2) exists. Fails
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% without error if this is not the case. The predicate is intended
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% to be used with :- if, as in the example below. See also
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% source_exports/2.
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%
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% ==
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% :- if(exists_source(library(error))).
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% :- use_module_library(error).
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% :- endif.
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% ==
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exists_source(Source) :-
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exists_source(Source, _Path).
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exists_source(Source, Path) :-
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absolute_file_name(Source, Path,
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[ file_type(prolog),
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access(read),
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file_errors(fail)
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]).
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%% source_exports(+Source, +Export) is semidet.
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%% source_exports(+Source, -Export) is nondet.
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%
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% True if Source exports Export. Fails without error if this is
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% not the case. See also exists_source/1.
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%
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% @tbd Should we also allow for source_exports(-Source, +Export)?
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source_exports(Source, Export) :-
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open_source(Source, In),
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catch(call_cleanup(exports(In, Exports), close(In)), _, fail),
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( ground(Export)
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-> memberchk(Export, Exports)
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; member(Export, Exports)
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).
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%% open_source(+Source, -In:stream) is semidet.
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%
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% Open a source location.
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open_source(File, In) :-
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exists_source(File, Path),
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open(Path, read, In),
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( peek_char(In, #)
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-> skip(In, 10)
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; true
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).
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exports(In, Exports) :-
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read(In, Term),
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Term = (:- module(_Name, Exports)).
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