ActionScript 3 allows for the development of custom packages and classes that can be reused and shared with others. Many of these classes and packages already have been posted and documented in the MathDL Flash Forum. This tutorial will give some examples of using the custom MathParser class that is particularly broadly applicable for math and science applications. There is a very well written tutorial on how to use the parser in connection with graphing applications, so this tutorial will address the MathParser class on its own substantial merit.
To use these classes you will need to download and extract the class files from bkde.zip. The folder bkde should be in the same directory as any fla file you create needing the MathParser class.