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yap-6.3/CHR/chr/sbag_a.pl
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Prolog

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Constraint Handling Rules version 2.2 %
% %
% (c) Copyright 1996-98 %
% LMU, Muenchen %
% %
% File: sbag_a.pl %
% Author: Christian Holzbaur christian@ai.univie.ac.at %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% bags of suspensions
%
:- module( sbag,
[
iter_init/2,
iter_last/1,
iter_next/3,
list_to_sbag/2,
sbag_empty/1,
sbag_member/2,
sbag_union/3,
sbag_add_element/3,
sbag_del_element/3
]).
:- use_module( library(assoc),
[
assoc_to_list/2,
put_assoc/4,
del_assoc/4,
gen_assoc/3,
list_to_assoc/2,
ord_list_to_assoc/2
]).
% -----------------------------------------------------------------
%
% *** MACROS ***
%
:- multifile
user:goal_expansion/3.
:- dynamic
user:goal_expansion/3.
%
user:goal_expansion( iter_init(A,B), _, sbag:down(A,[],B)).
user:goal_expansion( iter_last([]), _, true).
user:goal_expansion( iter_next([A|B],C,D), _, sbag:iter_next(A,B,D,C)).
user:goal_expansion( sbag_empty(A), _, A==t).
% -----------------------------------------------------------------
iter_init( Assoc, Contin) :-
down( Assoc, [], Contin).
iter_last( []).
sbag_empty( B) :- B == t.
%
% fails for empty
%
iter_next( [Node|Cont], Elem, Next) :-
iter_next( Node, Cont, Next, Elem).
iter_next( t(K,_,_,_,R), Cont, Next, K) :- % cf. assoc.pl
down( R, Cont, Next).
/*
( R==t,L==t -> Next=Cont
; R==t -> Next=Cont % Next=[t(K,V,0,t,t)|Cont]
; down( R, Cont, Next)
).
*/
down( t, Ci, Ci).
down( Node, Ci, Co) :-
Node = t(_,_,_,L,_),
down( L, [Node|Ci], Co).
list_to_sbag( L, A) :-
list_to_sbag( L, t, A).
list_to_sbag([], Assoc, Assoc).
list_to_sbag([X|Xs], Assoc0, Assoc) :-
put_assoc( X, Assoc0, 0, Assoc1),
list_to_sbag( Xs, Assoc1, Assoc).
sbag_member( Elem, A) :-
gen_assoc( Elem, A, _).
sbag_union( A, B, C) :-
assoc_to_list( A, As),
assoc_to_list( B, Bs),
prolog:merge( As, Bs, Cs),
ord_list_to_assoc( Cs, C).
sbag_add_element( S1, E, S2) :- put_assoc( E, S1, 0, S2).
sbag_del_element( S1, E, S2) :- del_assoc( E, S1, _, S2).
end_of_file.
% -----------------------------------------------------------------
test( N) :-
length( L, N),
list_to_assoc( L, A),
down( A, [], C),
a2l( C, L1),
assoc_to_list( A, L2),
( L1==L1 -> true ; raise_exception( mismatch(L1,L2))).
bug(L) :-
A = t(c,0,0,t(b,0,-1,t(a,0,0,t,t),t),
t(e,0,0,t(d,0,0,t,t),
t(f,0,0,t,t))),
iter_init( A, S),
a2l( S, L).
a2l( S, []) :- iter_last( S).
a2l( S, [X|Xs]) :-
iter_next( S, X, N),
a2l( N, Xs).