MACROMEDIA FLASH MX, Reference

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36 Chapter 2: ActionScript Language Reference
& (bitwise AND)
Availability
Flash Player 5. In Flash 4, the AND (&) operator was used for concatenating strings. In Flash 5
and later, the AND (&) operator is a bitwise AND, and you must use the addition (
+)
operator to
concatenate strings. Flash 4 files that use the AND (
&)
operator are automatically updated to use
addition (+) operator when imported into the Flash 5 or later authoring environment.
Usage
expression1 & expression2
Parameters
None.
Returns
A 32-bit integer.
Description
Operator (bitwise); converts
expression1
and
expression2
to 32-bit unsigned integers, and
performs a Boolean AND operation on each bit of the integer parameters. Floating-point
numbers are converted to integers by discarding any digits after the decimal point. The result is a
new 32-bit integer.
Positive integers are converted to an unsigned hex value with a maximum value of 4294967295 or
0xFFFFFFFF; values larger than the maximum have their most significant digits discarded when
they are converted so the value is still 32-bit. Negative numbers are converted to an unsigned hex
value using the two’s complement notation, with the minimum being -2147483648 or
0x800000000; numbers less than the minimum are converted to two’s complement with greater
precision and then have the most significant digits discarded as well.
The return value is interpreted as a two’s complement number with sign, so the return is an
integer in the range -2147483648 to 2147483647.
For more information, see “Operator precedence and associativity” in Using ActionScript in Flash .
Example
The following example compares the bit representation of the numbers and returns 1 only if both
bits at the same position are 1. In this ActionScript, you add 13 (binary 1101) and 11 (binary
1011) and return 1 only in the position where both numbers have a 1.
var insert:Number = 13;
var update:Number = 11;
trace(insert & update);// output : 9 (or 1001 binary)
In the numbers 13 and 11 the result is 9 because only the first and last positions in both numbers
have the number 1.
The following examples show the behavior of the return value conversion:
trace(0xFFFFFFFF); // 4294967295
trace(0xFFFFFFFF & 0xFFFFFFFF); // -1