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yap-6.3/swi/library/nb_set.pl
Vítor Santos Costa 3009987985 update docs
2014-09-11 14:06:57 -05:00

127 lines
3.4 KiB
Prolog

/* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: jan@science.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2005, 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(nb_set,
[ empty_nb_set/1, % -EmptySet
add_nb_set/2, % +Key, !Set
add_nb_set/3, % +Key, !Set, ?New
gen_nb_set/2, % +Set, -Key
size_nb_set/2, % +Set, -Size
nb_set_to_list/2 % +Set, -List
]).
/** <module> Non-backtrackable sets
@ingroup SWILibrary
This library provides a non-backtrackabe set. It is based on
nb_setarg/3. See the SWI-Prolog manual for details.
@author Jan Wielemaker
@tbd Base this work on AVL trees rather then unbalanced trees.
*/
/*******************************
* NON-BACKTRACKABLE SETS *
*******************************/
%% empty_nb_set(-Set)
%
% Create an empty non-backtrackable set.
empty_nb_set(nb_set(t)).
%% add_nb_set(+Key, !Set) is det.
%% add_nb_set(+Key, !Set, ?New) is semidet.
%
% Insert an element into the set. If the element is already in the
% set, nothing happens. New is =true= if Key was added as a new
% element to the set and =false= otherwise.
add_nb_set(Key, Set) :-
add_nb_set(Key, Set, _).
add_nb_set(Key, Set, New) :-
( empty_nb_set(Set)
-> New = true,
nb_setarg(1, Set, t(Key, t, t))
; arg(1, Set, Tree),
'$btree_find_node'(Key, Tree, Node, Arg),
( Arg == 1
-> New = false
; New = true,
nb_setarg(Arg, Node, t(Key, t, t))
)
).
%% nb_set_to_list(+Set, -List)
%
% Get the elements of a an nb_set. List is sorted to the standard
% order of terms.
nb_set_to_list(nb_set(Set), List) :-
phrase(nb_set_to_list(Set), List).
nb_set_to_list(t) -->
[].
nb_set_to_list(t(Val, Left, Right)) -->
nb_set_to_list(Left),
[Val],
nb_set_to_list(Right).
%% gen_nb_set(+Set, -Key)
%
% Enumerate the members of a set in the standard order of terms.
gen_nb_set(nb_set(Tree), Key) :-
gen_set(Tree, Key).
gen_set(t(Val, Left, Right), Key) :-
( gen_set(Left, Key)
; Key = Val
; gen_set(Right, Key)
).
%% size_nb_set(+Set, -Size)
%
% Unify Size with the number of elements in the set
size_nb_set(nb_set(Tree), Size) :-
set_size(Tree, Size).
set_size(t, 0).
set_size(t(_,L,R), Size) :-
set_size(L, SL),
set_size(R, SR),
Size is SL+SR+1.