[ library(fd) | The ECLiPSe Libraries | Reference Manual | Alphabetic Index ]

# ?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