/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 2007-2020, University of Amsterdam
CWI, Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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*/
:- module(prolog_dialect,
[ expects_dialect/1, % +Dialect
exists_source/1, % +Source
source_exports/2 % +Source, ?Export
]).
:- autoload(library(error),[must_be/2]).
:- autoload(library(lists),[member/2]).
/** <module> Support multiple Prolog dialects
The idea for this predicate was raised by Vitor Santos Costa in a
discussion to reach as a portability framework between SWI-Prolog and
YAP.
This library defines :- expects_dialect/1, telling the system for which
Prolog dialect was written, as well as useful tests in conditional
compilation:
* exists_source/1
* source_exports/2
@see if/1, require/1, term_expansion/2, goal_expansion/2.
@author Jan Wielemaker
@author Vitor Santos Costa
*/
%! expects_dialect(+Dialect:atom) is det.
%
% Tell Prolog all subsequent code to the end of the file or the
% next :- expects_dialect/1 directive is written for the indicated
% Dialect. The current dialect is available through
% prolog_load_context/2.
%
% @tbd Should we setup the dialect module only as autoload for
% the current module?
expects_dialect(Dialect) :-
must_be(atom, Dialect),
set_prolog_flag(emulated_dialect, Dialect),
( Dialect == swi
-> true
; attach_dialect(Dialect)
).
attach_dialect(Dialect) :-
exists_source(library(dialect/Dialect)),
!,
prolog_load_context(module, Module),
use_module(Module:library(dialect/Dialect)),
( current_predicate(Dialect:setup_dialect/0)
-> Dialect:setup_dialect
; true
).
attach_dialect(_).
%! source_exports(+Source, +Export) is semidet.
%! source_exports(+Source, -Export) is nondet.
%
% True if Source exports Export. Fails without error if this is
% not the case. See also exists_source/1.
%
% @tbd Should we also allow for source_exports(-Source, +Export)?
source_exports(Source, Export) :-
open_source(Source, In),
catch(call_cleanup(exports(In, Exports), close(In)), _, fail),
( ground(Export)
-> memberchk(Export, Exports)
; member(Export, Exports)
).
%! open_source(+Source, -In:stream) is semidet.
%
% Open a source location.
open_source(File, In) :-
exists_source(File, Path),
open(Path, read, In),
( peek_char(In, #)
-> skip(In, 10)
; true
).
exports(In, Exports) :-
read(In, Term),
Term = (:- module(_Name, Exports)).