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chr_labeling

Activates the built-in labeling feature for constraint handling rules.

Description

The constraint handling rule run-time system provides built-in labeling user-defined constraints. The built-in labeling is invoked by calling the built-in predicate chr_labeling/0. Once called, whenever no more constraint handling is possible, the built-in labeling will choose a constraint goal whose label_with declaration is satisfied for labeling. It will introduce choices using the clauses of the constraint.

Fail Conditions

None, only on backtracking.

Resatisfiable

Yes.

Examples

   A query without and with built-in labeling:
[eclipse]: minimum(X,Y,Z), maximum(X,Y,W), Z neq W.

X = _g357
Y = _g389
Z = _g421
W = _g1227

Constraints:
(1) minimum(_g357, _g389, _g421)
(2) _g421 leq _g357
(3) _g421 leq _g389
(4) maximum(_g357, _g389, _g1227)
(5) _g357 leq _g1227
(7) _g389 leq _g1227
(10) _g421 lss _g1227

yes.

[eclipse]: minimum(X,Y,Z), maximum(X,Y,W),
           Z neq W, chr_labeling.

X = Z = _g363
Y = W = _g395

Constraints:
(10) _g363 lss _g395

     More? (;)

X = W = _g363
Y = Z = _g395

Constraints:
(17) _g395 lss _g363
yes.

See Also

chr_label_with / 1, chr_resolve / 1, chr_get_constraint / 1, chr_get_constraint / 2