Evaluation Constraint Predicates

These constraint predicates evaluate the given constraint expression and associate its truth value with a boolean variable. They can be very useful for defining more complex constraints. They can be used both to test entailment of a constraint and to impose a constraint or its negation on the current constraint store.

?B isd +Expr

B is equal to 1 iff the constraint expression Expr is true, 0 otherwise. This predicate is the constraint counterpart of is/2 -- it takes a constraint expression, transforms all its subexpressions into calls to predicates with arity one higher and combines the resulting boolean values to yield B. For instance,

B isd X #= Y

is equivalent to

#=(X, Y, B)

#<(?T1, ?T2, ?B)

B is equal to 1 iff the value of the rational term T1 is less than the value of the rational term T2, 0 otherwise.

#<=(?T1, ?T2, ?B)

B is equal to 1 iff the value of the rational term T1 is less than or equal to the value of the rational term T2, 0 otherwise.

#=(?T1, ?T2, ?B)

B is equal to 1 iff the value of the rational term T1 is equal to the value of the rational term T2, 0 otherwise.

#\=(?T1, ?T2, ?B)

B is equal to 1 iff the value of the rational term T1 is different from the value of the rational term T2, 0 otherwise.

#>(?T1, ?T2, ?B)

B is equal to 1 iff the value of the rational term T1 is greater than the value of the rational term T2, 0 otherwise.

#>=(?T1, ?T2, ?B)

B is equal to 1 iff the value of the rational term T1 is greater than or equal to the value of the rational term T2, 0 otherwise.

#/\(+E1, +E2, ?B)

B is equal to 1 iff both constraint expressions E1 and E2 are true, 0 otherwise.

#\/(+E1, +E2, ?B)

B is equal to 1 iff at least one of the constraint expressions E1 and E2 is true, 0 otherwise.

#<=>(+E1, +E2, ?B)

B is equal to 1 iff the constraint expression E1 is equivalent to the constraint expression E2, 0 otherwise.

#=>(+E1, +E2, ?B)

B is equal to 1 iff the constraint expression E1 implies the constraint expression E2, 0 otherwise.

#\+(+E1, ?B)

B is equal to 1 iff E1 is false, 0 otherwise.