CHAPTER 15: Expressions

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15.23 Conditional-Or Operator ||

The || operator is like | (S15.21.2), but evaluates its right-hand operand only if the value of its left-hand operand is false . It is syntactically left-associative (it groups left-to-right). It is fully associative with respect to both side effects and result value; that is, for any expressions a, b, and c, evaluation of the expression (( a)||( b))||( c) produces the same result, with the same side effects occurring in the same order, as evaluation of the expression ( a)||(( b)||( c)) .

ConditionalOrExpression:

	ConditionalAndExpression

	ConditionalOrExpression || ConditionalAndExpression

Each operand of || must be of type boolean, or a compile-time error occurs. The type of a conditional-or expression is always boolean .

At run time, the left-hand operand expression is evaluated first; if its value is true , the value of the conditional-or expression is true and the right-hand operand expression is not evaluated. If the value of the left-hand operand is false , then the right-hand expression is evaluated and its value becomes the value of the conditional-or expression. Thus, || computes the same result as | on boolean operands. It differs only in that the right-hand operand expression is evaluated conditionally rather than always.