85 lines
2.4 KiB
Plaintext
85 lines
2.4 KiB
Plaintext
/* $Id$
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Part of CHR (Constraint Handling Rules)
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Author: Tom Schrijvers
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E-mail: Tom.Schrijvers@cs.kuleuven.be
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WWW: http://www.swi-prolog.org
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Copyright (C): 2003-2004, K.U. Leuven
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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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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(chrdif,[chrdif/2]).
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:- use_module(library(chr)).
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:- constraints dif/2, dif2/3, or/2, or_seq/2, del_or/1.
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chrdif(X,Y) :- dif(X,Y).
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dif(X,Y) <=> compound(X), compound(Y) | dif1(X,Y).
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dif(X,X) <=> fail.
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dif(X,Y) <=> nonvar(X), nonvar(Y) /* X \== Y holds */ | true.
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dif1(X,Y) :-
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( functor(X,F,A),
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functor(Y,F,A) ->
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X =.. [_|XL],
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Y =.. [_|YL],
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dif1l(XL,YL,A)
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;
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true
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).
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dif1l(Xs,Ys,N) :-
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or(Or,N),
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dif1l_2(Xs,Ys,Or).
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dif1l_2([],[],_).
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dif1l_2([X|Xs],[Y|Ys],Or) :-
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dif2(X,Y,Or),
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dif1l_2(Xs,Ys,Or).
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or_seq(OrP,Or) \ or(Or,0), or(OrP,N) <=> M is N - 1, or_seq(OrP,M).
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or(_,0) <=> fail.
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dif2(X,Y,Or) <=> compound(X), compound(Y) | dif3(X,Y,Or).
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dif2(X,X,Or), or(Or,N) <=> M is N - 1, or(Or,M).
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dif2(X,Y,Or) <=> nonvar(X), nonvar(Y) /* X \== Y holds */ | del_or(Or).
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del_or(Or) \ or_seq(OrP,Or) <=> del_or(OrP).
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del_or(Or) \ or_seq(Or,OrC) <=> del_or(OrC).
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del_or(Or) \ or(Or,_) <=> true.
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del_or(Or) \ dif2(_,_,Or) <=> true.
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del_or(Or) <=> true.
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dif3(X,Y,Or) :-
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( functor(X,F,A),
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functor(Y,F,A) ->
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X =.. [_|XL],
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Y =.. [_|YL],
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or_seq(Or,Or2),
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dif1l(XL,YL,A)
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;
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del_or(Or)
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).
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