ActionScript for Flash MX: The Definitive Guide, Second Edition

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Nested Functions

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Which approach is better—recursive or nonrecursive—depends on the problem.

Some problems are solved more easily using recursion, but recursion can be slower

than nonrecursive solutions. Recursion is best used when you don’t know how

deeply a data structure may be nested. For example, suppose you wanted to list all

the files within a subdirectory, including listing all files within any nested subdirec-

tory, ad infinitum. It would be inconvenient to write a general solution that worked

for any number of subdirectories without resorting to recursion. A recursive solution

might look like this in pseudocode:

function listFiles (directoryName) {

do (check the next item in directoryName) {

if (this item is a subDirectory itself) {

// Recursively call this function with the new subdirectory

listFiles(subDirectoryName);

} else {

// Display the name of this file

trace(filename);

}

} while(there are still items to check);

}

When we consider the XML object the Language Reference, we’ll use recursion to list

all the elements in an XML document.

Nested Functions

In ActionScript, functions can be declared within functions. Example 9-10 creates a

function, showFullName( ), with two nested functions, showFirstName( ) and

showLastName( ).

Inside showFullName( ), the nested functions ...