/usr/lib/swi-prolog/library/dialect.pl is in swi-prolog-nox 5.10.4-3ubuntu1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 | /* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: wielemak@science.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 2007, University of Amsterdam
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(prolog_dialect,
[ expects_dialect/1, % +Dialect
exists_source/1, % +Source
source_exports/2 % +Source, ?Export
]).
:- use_module(library(error)).
:- use_module(library(lists)).
/** <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(_).
%% exists_source(+Source) is semidet.
%
% True if Source (a term valid for load_files/2) exists. Fails
% without error if this is not the case. The predicate is intended
% to be used with :- if, as in the example below. See also
% source_exports/2.
%
% ==
% :- if(exists_source(library(error))).
% :- use_module_library(error).
% :- endif.
% ==
exists_source(Source) :-
exists_source(Source, _Path).
exists_source(Source, Path) :-
absolute_file_name(Source, Path,
[ file_type(prolog),
access(read),
file_errors(fail)
]).
%% 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)).
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