Functional Programming Patterns in Scala and Clojure

Pattern 16

Function Builder

Intent

To create a function that itself creates functions, allowing us to synthesize behaviors on the fly

Overview

Sometimes we’ve got a function that performs a useful action, and we need a function that performs some other, related action. We might have a vowel? predicate that returns true when a vowel is passed in and need a consonant? that does the same for consonants.

Other times, we’ve got some data that we need to turn into an action. We might have a discount percentage and need a function that can apply that discount to a set of items.

With Function Builder, we write a function that takes our data or function (though, as we’ve seen, the distinction between functions and data is blurry) and uses it to create ...