C9 Lectures: Dr. Erik Meijer - Functional Programming Fundamentals Chapter 6 of 13

We've kicked off C9 Lectures with a journey into the world of Functional Programming with functional language purist and high priest of the lambda calculus, Dr. Erik Meijer (you can thank Erik for many of the functional constructs that have shown up in languages like C# and VB.NET. When you use LINQ, thank Erik in addition to Anders). We will release a new chapter in this series every Thursday. In Chapter 6, Dr. Meijer guides us through the world of recursive functions. In Haskell, functions can be defined in terms of themselves. Such functions are called recursive. For example: factorial 0 = 1 factorial (n+1) = (n+1) * factorial n factorial maps 0 to 1, and any other positive integer to the product of itself and the factorial of its predecessor. Some functions, such as factorial, are simpler to define in terms of other functions. As we shall see, however, many functions can naturally be defined in terms of themselves. Properties of functions defined using recursion can be proved using the simple but powerful mathematical technique of induction.