Get Programming with Haskell

Lesson 19. The Maybe type: dealing with missing values

After reading lesson 19, you’ll be able to

• Understand the Maybe type
• Use the Maybe type to handle missing values
• Design programs with Maybe types

Just as type classes can often be much more abstract than interfaces in OOP, parameterized types play a much larger role than generics do in most languages. This lesson introduces an important parameterized type: Maybe. Unlike List or Map, which represent containers for values, Maybe is the first of many types you’ll see that represents a context for a value. Maybe types represent values that might be missing. In most languages, a missing value is represented by the null value. By using a context representing a value that might be missing, ...