MACROMEDIA FLASH 8-FLASH, Reference

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-= (subtraction assignment) 109
Description
Operator (arithmetic compound assignment); assigns
expression1
the value of
expression1 - expression2
. No value is returned.
For example, the following two statements are the same:
x -= y;
x = x - y;
String expressions must be converted to numbers; otherwise, -1 is returned.
Example
Usage 1: The following example uses the
-=
operator to subtract 10 from 5 and assign the
result to the variable
x
:
x = 2;
y = 3;
x -= y
trace(x);// output: -1
Usage 2: The following example shows how strings are converted to numbers:
x = "2";
y = "5";
x -= y;
trace(x);// output: -3