User Guide

120 Chapter 5: ActionScript Core Language Elements

-= (subtraction assignment)

Availability

Flash Player 4.

Usage

expression1 -= expression2

Parameters

expression1,expression2

A number or expression that evaluates to a number.

Returns

A number.

Description

Operator (arithmetic compound assignment); assigns expression1 the value of expression1 -

expression2. For example, the following two statements are equivalent:

x -= y;

x = x - y;

String expressions must be converted to numbers; otherwise, NaN (not a number) is returned.

For more information, see “Operator precedence and associativity” on page 32.

Example

The following example uses the subtraction assignment (-=) operator to subtract 10 from 5 and

assign the result to the variable

var x:Number = 5;

var y:Number = 10;

x -= y;

trace(x); // output: -5

The following example shows how strings are converted to numbers:

var x:String = "5";

var y:String = "10";

x -= y;

trace(x); // output: -5