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82 Chapter 5: ActionScript Core Language Elements
++ (increment)
Availability
Flash Player 4.
Usage
++expression
exp+
Parameters
expression
A number or a variable that evaluates to a number.
Returns
A number.
Description
Operator (arithmetic); a pre-increment and post-increment unary operator that adds 1 to
expression
. The
expression
can be a variable, element in an array, or property of an object.
The pre-increment form of the operator (
++expression
) adds 1 to
expression
and returns the
result. The post-increment form of the operator (
exp+
) adds 1 to
expression
and
returns the initial value of
expression
(the value prior to the addition).
The pre-increment form of the operator increments
x
to 2 (
x + 1 = 2
) and returns the result
as
y
:
var x:Number = 1;
var y:Number = ++x;
trace("x:"+x);//traces x:2
trace("y:"+y);//traces y:2
The post-increment form of the operator increments
x
to 2 (
x + 1 = 2
) and returns the original
value of
x
as the result
y
:
var x:Number = 1;
var y:Number = x++;
trace("x:"+x);//traces x:2
trace("y:"+y);//traces y:1
For more information, see “Operator precedence and associativity” on page 32 .
Example
The following example uses ++ as a post-increment operator to make a
while
loop run five times:
var i:Number = 0;
while (i++<5) {
trace("this is execution "+i);
}
/* output:
this is execution 1
this is execution 2
this is execution 3
this is execution 4