HP C/iX Reference Manual (31506-90011)

Chapter 5 81
Expressions
Logical AND Operator
Logical AND Operator
The logical AND operator (&&) performs the logical AND function on its operands.
Syntax
logical-AND-expression :=
inclusive-OR-expression
logical-AND-expression && inclusive-OR-expression
Description
Each of the operands must have scalar type. The type of the left operand need not be
related to the type of the right operand. The result has type int and has a value of 1 if both
of its operands compare unequal to 0, and 0 otherwise. The result is not an lvalue.
The logical AND operator guarantees left-to-right evaluation. If the first operand
compares equal to zero, the second operand is not evaluated.
This feature is useful for pointer operations involving pointers that can be NULL. For
example, the following statement:
if(p!=NULL && *p=='A') *p='B';
The first operand tests to see if pointer p is NULL. If p is NULL, an indirect reference
could cause a memory access violation. If p is non-NULL, the second operand is safe to
evaluate. The second expression checks to see if p points to the character 'A'. If the
second expression is true, the expression is true and the character that p points to is
changed to 'B'. Had the pointer been NULL, the if statement would have failed and the
pointer would not be used indirectly to test for the 'A' character.
Example
var1 && var2