ActionScript for Flash MX: The Definitive Guide, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

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Chapter 15

CHAPTER 15

Lexical Structure

The lexical structure of a language is the set of rules that govern its syntactic compo-

sition. We must follow these rules when writing the source code of our scripts.

Whitespace

The tab, space, and carriage return (i.e., line break) characters are used in Action-

Script just as they are used in English: to separate words from each other so that they

don’t all runtogetherlikethis. In programmer-speak, these characters are known as

whitespace and are used in source code to separate tokens (the keywords, identifiers,

and expressions roughly akin to words, phrases, and sentences in English). Here is

an example of incorrect and correct whitespace usage:

varx; // Oops! No whitespace between the var keyword and the variable x.

var x; // That's better...because of the whitespace, the interpreter

// can now understand our code.

Whitespace is optional when there is some other delimiter (separator) that tells

ActionScript where one token ends and another begins. The following code is quite

legitimate, because the operators =, +, and / separate

x, 10, 5, and y from one

another:

x=10+5/y; // Crowded, but legitimate

x = 10 + 5 / y; // Easier to read, but the same as above

Similarly, whitespace is optional when there are other characters—such as square

brackets, ...