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Essential ActionScript 3.0 by Colin Moock

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Boolean Logic

Early in this chapter, we saw how to make logical decisions using test expressions that yield Boolean values. The decisions were based on a single factor, such as "if language is "english", then display "Hello". But not all programming logic is so simple. Programs often need to consider multiple factors in branching logic (i.e., decision making). To manage multiple factors in a test expression, we use the Boolean operators: || (logical OR) and && (logical AND).

Logical OR

The logical OR operator is most commonly used to initiate some action when at least one of two conditions is met. For example, "If I am hungry or I am thirsty, I'll go to the kitchen." The symbol for logical OR is made using two "pipe" characters: ||. Typically, the pipe character (|) is accessible using the Shift key and the Backslash (\) key in the upper right of most Western keyboards, where it may be depicted as a dashed vertical line. Logical OR has the following general form:

expression1 || expression2

When both expression1 and expression2 are Boolean values or evaluate to Boolean values, logical OR returns true if either expression is true and returns false only if both expression are false. In summary:

true  || false   // true because first operand is true
false || true    // true because second operand is true
true  || true    // true (however, either operand being true is sufficient)
false || false   // false because both operands are false

When expression1 is not a Boolean value, ActionScript first converts ...

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