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# ?C1 #=> ?C2

The constraint expression C1 implies the constraint expression C2.

?C1
  An arithmetic constraint expression.
?C2
  An arithmetic constraint expression.

## Description

This constraint states that the constraint expression C1 implies the constraint expression C2. If this is already the case, it simply succeeds. Otherwise it is suspended and after each domain change that may cause C1 to succeed, it is woken and re-evaluated. If C1 is true, C2 is imposed as a constraint.

### Fail Conditions

Fails if C1 is true and C2 is false.

### Resatisfiable

No.

## See Also

#\/ / 2, #/\ / 2, #<=> / 2, #\+ / 1