ActionScript: The Definitive Guide

Chapter 14. Lexical Structure

The lexical structure of a language is the set of rules that govern its syntactic composition. 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 ActionScript just like they are 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 keyword var and the variable x.
var x  // That's better...because of the whitespace the interpreter
       // can now read 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, parentheses, curly braces, commas, and greater-than or less-than signs to act as delimiters. These are all perfectly legal if somewhat claustrophobic:

for(var i=0;i<10;i++){trace(i);} if(x==7){y=[1,2,3,4,5,6,7,8,9,10];} myMeth=function(arg1,arg2,arg3){trace(arg1+arg2+arg3);}; ...