119 lines
3.8 KiB
Prolog
119 lines
3.8 KiB
Prolog
/* $Id: option.pl,v 1.1 2008-02-12 17:03:53 vsc Exp $
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Part of SWI-Prolog
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Author: Jan Wielemaker
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E-mail: jan@swi.psy.uva.nl
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WWW: http://www.swi-prolog.org
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Copyright (C): 1985-2002, University of Amsterdam
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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As a special exception, if you link this library with other files,
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compiled with a Free Software compiler, to produce an executable, this
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library does not by itself cause the resulting executable to be covered
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by the GNU General Public License. This exception does not however
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invalidate any other reasons why the executable file might be covered by
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the GNU General Public License.
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*/
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:- module(swi_option,
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[ option/2, % +Term, +List
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option/3, % +Term, +List, +Default
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select_option/3, % +Term, +Options, -RestOpts
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select_option/4 % +Term, +Options, -RestOpts, +Default
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]).
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:- use_module(library(lists)).
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%% option(?Option, +OptionList, +Default)
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%
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% Get an option from a OptionList. OptionList can use the
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% Name=Value as well as the Name(Value) convention.
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%
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% @param Option Term of the form Name(?Value).
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option(Opt, Options, Default) :- % make option processing stead-fast
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arg(1, Opt, OptVal),
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nonvar(OptVal), !,
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functor(Opt, OptName, 1),
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functor(Gen, OptName, 1),
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option(Gen, Options, Default),
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Opt = Gen.
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option(Opt, Options, _) :-
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get_option(Opt, Options), !.
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option(Opt, _, Default) :-
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arg(1, Opt, Default).
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%% option(?Option, +OptionList)
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%
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% Get an option from a OptionList. OptionList can use the
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% Name=Value as well as the Name(Value) convention. Fails silently
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% if the option does not appear in OptionList.
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%
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% @param Option Term of the form Name(?Value).
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option(Opt, Options) :- % make option processing stead-fast
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arg(1, Opt, OptVal),
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nonvar(OptVal), !,
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functor(Opt, OptName, 1),
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functor(Gen, OptName, 1),
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option(Gen, Options),
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Opt = Gen.
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option(Opt, Options) :-
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get_option(Opt, Options), !.
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get_option(Opt, Options) :-
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memberchk(Opt, Options), !.
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get_option(Opt, Options) :-
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functor(Opt, OptName, 1),
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arg(1, Opt, OptVal),
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memberchk(OptName=OptVal, Options), !.
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%% select_option(?Option, +Options, -RestOptions) is semidet.
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%
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% As option/2, removing the matching option from Options and
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% unifying the remaining options with RestOptions.
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select_option(Opt, Options0, Options) :- % stead-fast
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arg(1, Opt, OptVal),
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nonvar(OptVal), !,
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functor(Opt, OptName, 1),
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functor(Gen, OptName, 1),
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select_option(Gen, Options0, Options),
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Opt = Gen.
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select_option(Opt, Options0, Options) :-
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get_option(Opt, Options0, Options), !.
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get_option(Opt, Options0, Options) :-
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select(Opt, Options0, Options), !.
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get_option(Opt, Options0, Options) :-
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functor(Opt, OptName, 1),
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arg(1, Opt, OptVal),
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select(OptName=OptVal, Options0, Options), !.
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%% select_option(?Option, +Options, -RestOptions, +Default) is det.
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%
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% As select_option/3, but if Option is not in Options, its value
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% is unified with Default and RestOptions with Options.
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select_option(Option, Options, RestOptions, _Default) :-
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select_option(Option, Options, RestOptions), !.
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select_option(Option, Options, Options, Default) :-
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arg(1, Option, Default).
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