and expression - xtclang/xvm GitHub Wiki

The logical “and” expression is a well-known expression form:

a && b

The type of the expressions a and b must both be Boolean. The implicit type of the expression is Boolean.

If the expression a yields False, then the expression yields False^[1]. If the expression a yields True, then the expression yields the result of the expression b.

The expression short-circuits if either expression a or b short-circuits.

Definite assignment rules:

• The VAS before a is the VAS before the expression.
• The VAS before b is the VAS_T after a.
• The VAS after the expression is the join of the VAS_F after a and the VAS after b.
• The VAS_T after the expression is the VAS_T after b.
• The VAS_F after the expression is the join of the VAS_F after a and the VAS_F after b.

The AndExpression groups to the left, so a && b && c is treated as (a && b) && c:

    AndExpression:
        EqualityExpression
        AndExpression && EqualityExpression

This is often referred to as "short-circuit logic", but that term is not used here, in order to avoid confusion with the Ecstasy concept of short-circuiting expressions.↩