[ library(suspend) | Reference Manual | Alphabetic Index ]

?Expr1 and ?Expr2

Both Expr1 and Expr2 arithmetically evaluate to 1
Expr1
A boolean expression
Expr2
A boolean expression

Description

Suspends until both Expr1 and Expr2 are ground, and then both arguments are evaluated. Succeeds if both evaluate to 1.

Typically, the expressions contains reifiable constraints, in which case a corresponding reified constraint is set up, and the expression is replaced by the resulting boolean variable.

Modules

This predicate is sensitive to its module context (tool predicate, see @/2).

Fail Conditions

Expr1 or Expr2 do not both evaluate to 1

Exceptions

(24) number expected
Expr1 or Expr2 is not an arithmetic expression.

Examples

	?- B and 1, B = 1.
	B = 1
	Yes (0.00s cpu)

	?- B and 1, B = 0.
	No (0.00s cpu)

	% arguments are typically reifiable expressions:
	?- X > 5 and X < 7, X = 7.
	No (0.00s cpu)

	% the previous example is equivalent to:
	?- >(X,5,B1), <(X,7,B2), B1 and B2, X=7.
	No (0.00s cpu)

	% and/or/=>/neg are themselves reifiable:
	?- X > 5 and neg(X < 7), X = 7.
	X = 7
	Yes (0.00s cpu)

See Also

and / 3, or / 2, => / 2, neg / 1, ic : and / 2, gfd : and / 2