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ActionScript: The Definitive Guide by Colin Moock

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Arithmetic Operators

The arithmetic operators perform mathematical operations on numeric operands. If you use non-numeric operands with the arithmetic operators, ActionScript will attempt to convert the foreign data to a number. For example, false - true evaluates to -1 because false converts to the numeric value and true converts to 1. Similarly, the expression "3" * "5" results in the number 15, because the strings “3” and “5” are converted to the numbers 3 and 5 before the multiplication is performed. The + operator, however, presents a special case: when used with at least one string operand, it performs a string concatenation operation, not mathematical addition.

If an attempt to convert a non-numeric operand to a number fails, the operand will be set to the special numeric value NaN. This results in the entire operation yielding NaN. Refer to Table 3.1 for details on numeric conversion.

Addition

The addition operator returns the sum of its two operands:

                  operand1 + operand2

In order to return a meaningful mathematical result, the operands of + should be expressions that yield a numeric value, such as:

234 + 5          // Returns 239
(2 * 3 * 4) + 5  // Returns 29

The addition operator is unique among the arithmetic operators in that if one or both of its operands are strings, it performs as a string concatenation. Refer to Section 4.6.1 in Chapter 4.

Increment

A handy variation on addition, the increment operator accepts a single operand and simply adds 1 to its current value. Increment ...

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