HP C/iX Reference Manual (31506-90011)

Chapter 5 65

Expressions

Postﬁx Increment and Decrement Operators

The postﬁx increment operator ++ adds one to its operand after using its value. The postﬁx

decrement operator subtracts one from its operand after using its value.

Syntax

postfix-expression

Description

You can only apply postﬁx increment ++ and postﬁx decrement operators to an operand

that is a modiﬁable lvalue with scalar type. The result of a postﬁx increment or a postﬁx

decrement operation is not an lvalue.

The postﬁx-expression is incremented or decremented after its value is used. The

expression evaluates to the value of the object before the increment or decrement, not the

object's new value.

If the value of X is 2, after the expression A=X is evaluated, A is 2 and X is 3.

Avoid using postﬁx operators on a single operand appearing more than once in an

expression. The result of the following example is unpredictable:

*p = *p;

The C language does not deﬁne which expression is evaluated ﬁrst. The compiler can

choose to evaluate the left side of the = operator (saving the destination address) before

evaluating the right side. The result depends on the order of the subexpression evaluation.

Pointers are assumed to point into arrays. Incrementing (or decrementing) a pointer

causes the pointer to point to the next (or previous) element. This means, for example, that

incrementing a pointer to a structure causes the pointer to point to the next structure, not

the next byte within the structure. (Refer also to "Additive Operators" for information on

adding to pointers.)