Get Programming with Haskell

Lesson 28. A peek at the Applicative type class: using functions in a context

After reading lesson 28, you’ll be able to

• Build an application that handles missing data
• Extend the power of the Functor type class with the Applicative type
• Use Applicative to use one data model in many contexts

In the preceding lesson, you learned how the Functor type class allows you to perform computation inside a container such as List or a context such as Maybe and IO. The key method behind Functor is fmap (more commonly, the <$> operator), which works just like map on a list. In this lesson, you’ll work with a more powerful type class called Applicative. The Applicative type class extends the power of Functor by allowing you to use functions that are ...