Pattern matching on literals

Instead of using pattern variables, we can also write function equations using literal values as patterns. Here is an example:

isZero :: Int -> Bool
isZero 0 = True
isZero n = False

This function has two defining equations. The first one uses the numeric literal 0 as the pattern. We can read it as "if the argument to isZero is 0, the result is True". The second equation uses a pattern variable n, and says that the result to isZero should be False, for any value of n.

If a function has several defining equations, they will be applied from top to bottom for evaluating expressions involving the function’s application. However, an equation ...

Introduction

First Steps with Haskell

Techniques for Writing Functions

Working with Lists

Creating Data Types

Input and Output

Conclusion

Appendix

Pattern Matching on Literals

Pattern matching on literals