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?B isd ?C
The constraint expression C evaluates to the boolean value B.
- ?B
- A variable with domain 0..1.
- ?C
- An arithmetic constraint expression.
Description
   This is an evaluation constraint.  It states that the constraint
   expression C evaluates to the boolean value B, where the value 0 means
   false and 1 true.  This constraint can be used both to test the validity
   of the constraint expression (entailment test) and to impose this
   constraint or its negation.  For the former, B will be instantiated as
   soon as either the constraint expression or its negation is subsumed by
   the current state of its domain variables.  For the latter, when B is
   instantiated, then depending on its value, either the constraint
   expression or its negation will be imposed on its arguments.
Fail Conditions
   Fails if both C is true.
Resatisfiable
   No.
See Also
#=> / 3, #<=> / 3, #\/ / 3, #/\ / 3, is / 2