ychr-0.1.0.0: examples/leq.chr

% The canonical CHR example: a less-or-equal solver.
%
% Four rules cover the structural properties of a partial order:
%   - reflexivity:   leq(X, X) is trivially true.
%   - antisymmetry:  leq(X, Y) and leq(Y, X) force X = Y.
%   - idempotence:   two copies of leq(X, Y) collapse to one
%                    (simpagation: keep the left, remove the right).
%   - transitivity:  leq(X, Y) and leq(Y, Z) propagate leq(X, Z).
%
% Used by docs/tutorials/02-chr-primer.md as the worked example for
% all three rule kinds (simplification, simpagation, propagation).

:- module(order, [leq/2]).
:- 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).