MACROMEDIA FLASH 8-LEARNING ACTIONSCRIPT 2.0 IN FLASH, Manual

Page: 186 / 830

186 Syntax and Language Fundamentals
About postfix operators
The postfix operators take one operator and either increment or decrement the operator’s
value. Although these operators are unary operators, they are classified separately from the rest
of the unary operators because of their higher precedence and special behavior. For
information on unary operators, see
“About unary operators” on page 186 .
When you use a postfix operator as part of a larger expression, the expression’s value is
returned before the postfix operator is processed. For example, the following code shows how
the value of the expression
xNum++
is returned before the value is incremented.
var xNum:Number = 0;
trace(xNum++); // 0
trace(xNum); // 1
When you trace this code, the text in the Output panel reads:
0
1
The operators in this table have equal precedence:
About unary operators
Unary operators take one operand. The increment (
++
) and decrement (
--
) operators in this
group are prefix operators, which means that they appear before the operand in an expression.
They can also appear after the operand, in which case they are postfix operators. For
information on postfix operators, see “About postfix operators” on page 186 .
The prefix operators differ from the postfix counterparts because the increment or decrement
operation completes before the value of the overall expression is returned. For example, the
following code shows how the value of the expression
xNum++
is returned after the value is
incremented.
var xNum:Number = 0;
trace(++xNum); // 1
trace(xNum); // 1
Operator Operation performed
++
Increment (postfix)
--
Decrement (postfix)