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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%% simple constraint solver for inequalities between variables
%% thom fruehwirth ECRC 950519, LMU 980207, 980311
%%
%% ported to hProlog by Tom Schrijvers
:- module(leq,[leq/0]).
:- use_module(library(chr)).
:- chr_constraint leq/2.
reflexivity @ leq(X,X) <=> true.
antisymmetry @ leq(X,Y), leq(Y,X) <=> X = Y.
idempotence @ leq(X,Y) \ leq(X,Y) <=> true.
transitivity @ leq(X,Y), leq(Y,Z) ==> leq(X,Z).
leq :-
circle(X, Y, Z),
\+ attvar(X),
X == Y,
Y == Z.
circle(X, Y, Z) :-
leq(X, Y),
leq(Y, Z),
leq(Z, X).
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