/* 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, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 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 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- 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]). /** 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), ( Dialect == swi -> true ; attach_dialect(Dialect) ), set_prolog_flag(emulated_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)).