Functional Programming Patterns in Scala and Clojure

Pattern 17

Memoization

Intent

To cache the results of a pure function call to avoid performing the same computation more than once

Overview

Since pure functions always return the same value for given arguments, it’s possible to replace a pure function call with cached results.

We can do this manually by writing a function that keeps track of its previous arguments. When it’s called, it first checks its cache to see if it has already been called with the passed-in arguments. If it has, it returns the cached value. Otherwise, it performs the computation.

Some languages provide first-class support for Memoization using higher-order functions. Clojure, for instance, has a function called memoize that takes a function and returns a new one that ...