HP 3000 Manuals HP 3000 Manuals
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 ++
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.)