The old ECLiPSe CHR implementation features a label_with/1 construct
for labeling variables in CHR constraints. This feature has long since
been abandoned. However, a simple transformation is all that is required
to port the functionality.
label_with Constraint1 if Condition1.
...
label_with ConstraintN if ConditionN.
Constraint1 :- Body1.
...
ConstraintN :- BodyN.
is transformed into
:- chr_constraint my_labeling/0.
my_labeling \ Constraint1 <=> Condition1 | Body1.
...
my_labeling \ ConstraintN <=> ConditionN | BodyN.
my_labeling <=> true.
Be sure to put this code after all other rules in your program! With
my_labeling/0 (or another predicate name of your choosing) the labeling
is initiated, rather than ECLiPSe's chr_labeling/0 .
