In this chapter, you learn how to group statements into functions, which enables you to tell the computer how to do something, and to tell it only once. You won’t need to give it the same detailed instructions over and over. The chapter provides a thorough introduction to parameters and scoping, and you learn what recursion is and what it can do for your programs.

Laziness Is a Virtue

The programs we’ve written so far have been pretty small, but if you want to make something bigger, you’ll soon run into trouble. Consider what happens if you have written some code in one place and need to use it in another place as well. For example, let’s say ...

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