Recipe 4.1. Representing Numbers in Different Bases

Problem

You want to specify a value in binary, octal, or hexadecimal.

Solution

Hexadecimal literals start with 0x (where the first character is a zero, not an "oh"), and octal literals start with 0 (again, zero, not "oh"). Binary numbers can't be represented directly, but you can either specify their octal or hexadecimal equivalent or use the parseInt( ) function to convert a string to a number.

Discussion

You can represent numbers in ActionScript using whichever format is most convenient, such as decimal or hexadecimal notation. For example, if you set the value of the Sprite.rotation property, it is most convenient to use a decimal number:

rectangleSprite.rotation = 180;

On the other hand, hexadecimal numbers are useful for specifying RGB colors. For example, you can set the rgb value for a ColorTransform object in hexadecimal notation (in this example, 0xF612AB is a hex number representing a shade of pink):

var pink:ColorTransform = new ColorTransform(  );
pink.rgb = 0xF612AB;

Any numeric literal starting with 0X or 0x (where the first character is a zero, not an "oh") is presumed to be a hexadecimal number (i.e., hex or base-16). Allowable digits in a hexadecimal number are 0 through 9 and A through F (upper- and lowercase letters are equivalent, meaning 0xFF is the same as 0xff).

Any numeric literal starting with 0 (again, zero not "oh"), but not 0x or 0X, is presumed to be an octal number (i.e., base-8). Allowable digits in an octal number are 0 through 7; for example, 0777 is an octal number. Most developers don't ever use octal numbers in ActionScript. For most developers it's simply far more convenient to represent most numbers as decimal numbers (base-10), except color values for which it is generally more convenient to use hexadecimal representation. There aren't many common examples for which octal representation is more convenient than decimal or hexadecimal.

The only digits allowed in binary numbers (i.e., base-2) are 0 and 1. Although you can't specify a binary number directly, you can specify its hexadecimal equivalent. Four binary digits (bits) are equivalent to a single hex digit. For example, 1111 in binary is equivalent to F in hex (15 in decimal). The number 11111111 in binary is equivalent to FF in hex (255 in decimal). Binary numbers (or rather their hexadecimal equivalents) are most commonly used with ActionScript's bitwise operators (&, |, ^, >>, <<, and >>>).