140 lines
3.3 KiB
Prolog
140 lines
3.3 KiB
Prolog
/* $Id$
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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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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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% Binomial Heap imlementation based on
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%
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% Functional Binomial Queues
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% James F. King
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% University of Glasgow
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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:- module(binomialheap,
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[
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empty_q/1,
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insert_q/3,
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insert_list_q/3,
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delete_min_q/3,
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find_min_q/2
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]).
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:- use_module(library(lists),[reverse/2]).
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% data Tree a = Node a [Tree a]
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% type BinQueue a = [Maybe (Tree a)]
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% data Maybe a = Zero | One a
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% type Item = (Entry,Key)
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key(_-Key,Key).
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empty_q([]).
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meld_q(P,Q,R) :-
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meld_qc(P,Q,zero,R).
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meld_qc([],Q,zero,Q) :- !.
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meld_qc([],Q,C,R) :- !,
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meld_q(Q,[C],R).
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meld_qc(P,[],C,R) :- !,
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meld_qc([],P,C,R).
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meld_qc([zero|Ps],[zero|Qs],C,R) :- !,
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R = [C | Rs],
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meld_q(Ps,Qs,Rs).
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meld_qc([one(node(X,Xs))|Ps],[one(node(Y,Ys))|Qs],C,R) :- !,
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key(X,KX),
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key(Y,KY),
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( KX < KY ->
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T = node(X,[node(Y,Ys)|Xs])
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;
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T = node(Y,[node(X,Xs)|Ys])
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),
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R = [C|Rs],
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meld_qc(Ps,Qs,one(T),Rs).
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meld_qc([P|Ps],[Q|Qs],C,Rs) :-
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meld_qc([Q|Ps],[C|Qs],P,Rs).
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insert_q(Q,I,NQ) :-
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meld_q([one(node(I,[]))],Q,NQ).
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insert_list_q([],Q,Q).
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insert_list_q([I|Is],Q,NQ) :-
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insert_q(Q,I,Q1),
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insert_list_q(Is,Q1,NQ).
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min_tree([T|Ts],MT) :-
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min_tree_acc(Ts,T,MT).
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min_tree_acc([],MT,MT).
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min_tree_acc([T|Ts],Acc,MT) :-
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least(T,Acc,NAcc),
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min_tree_acc(Ts,NAcc,MT).
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least(zero,T,T) :- !.
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least(T,zero,T) :- !.
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least(one(node(X,Xs)),one(node(Y,Ys)),T) :-
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key(X,KX),
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key(Y,KY),
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( KX < KY ->
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T = one(node(X,Xs))
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;
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T = one(node(Y,Ys))
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).
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remove_tree([],_,[]).
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remove_tree([T|Ts],I,[NT|NTs]) :-
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( T == zero ->
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NT = T
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;
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T = one(node(X,_)),
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( X == I ->
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NT = zero
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;
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NT = T
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)
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),
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remove_tree(Ts,I,NTs).
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delete_min_q(Q,NQ,Min) :-
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min_tree(Q,one(node(Min,Ts))),
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remove_tree(Q,Min,Q1),
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reverse(Ts,RTs),
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make_ones(RTs,Q2),
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meld_q(Q2,Q1,NQ).
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make_ones([],[]).
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make_ones([N|Ns],[one(N)|RQ]) :-
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make_ones(Ns,RQ).
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find_min_q(Q,I) :-
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min_tree(Q,one(node(I,_))).
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