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/* $Id: ordsets.pl,v 1.2 2002/02/01 16:49:11 jan Exp $
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: jan@swi.psy.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2002, 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 Lesser 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(ordsets,
[ list_to_ord_set/2,
ord_intersect/2,
ord_add_element/3,
ord_subset/2,
ord_union/3
]).
:- use_module(library(oset)).
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Very incomplete implementation of Quintus/SICStus compatible ordset
library, partially based on the contributed SWI-Prolog library(oset).
Please complete the implementation and contribute it to the SWI-Prolog
community.
This library was implemented to run the threetap theorem prover.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
% list_to_ord_set(+List, -OrdSet)
%
% Transform a list into an ordered set. This is the same as
% sorting the list.
list_to_ord_set(List, Set) :-
sort(List, Set).
% ord_intersect(+Set1, +Set2)
%
% Succeed if both ordered sets have a non-empty intersection
ord_intersect([H1|T1], L2) :-
ord_intersect_(L2, H1, T1).
ord_intersect_([H2|T2], H1, T1) :-
compare(Order, H1, H2),
ord_intersect__(Order, H1, T1, H2, T2).
ord_intersect__(<, _H1, T1, H2, T2) :-
ord_intersect_(T1, H2, T2).
ord_intersect__(=, _H1, _T1, _H2, _T2).
ord_intersect__(>, H1, T1, _H2, T2) :-
ord_intersect_(T2, H1, T1).
% ord_add_element(+Set1, +Element, ?Set2)
%
% Insert an element into the set
ord_add_element(Set1, Element, Set2) :-
oset_addel(Set1, Element, Set2).
% ord_subset(+Sub, +Super)
%
% Is true if all element of Sub are in Super
ord_subset([], _).
ord_subset([H1|T1], [H2|T2]) :-
compare(Order, H1, H2),
ord_subset_(Order, H1, T1, T2).
ord_subset_(>, H1, T1, [H2|T2]) :-
compare(Order, H1, H2),
ord_subset_(Order, H1, T1, T2).
ord_subset_(=, _, T1, T2) :-
ord_subset(T1, T2).
% ord_union(+Set1, +Set2, ?Union)
%
% Union is the union of Set1 and Set2
ord_union(Set1, Set2, Union) :-
oset_union(Set1, Set2, Union).
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