Kotlin Standard Library Cookbook

How to do it...

1. Declare a Memoizer class responsible for caching the results:

class Memoizer<P, R> private constructor() {    private val map = ConcurrentHashMap<P, R>()    private fun doMemoize(function: (P) -> R):        (P) -> R = { param: P ->        map.computeIfAbsent(param) { param: P ->                    function(param)                }            }    companion object {        fun <T, U> memoize(function: (T) -> U): (T) -> U =                Memoizer<T, U>().doMemoize(function)    }}

2. Provide a memoized() extension function for the (P) -> R function type:

fun <P, R> ((P) -> R).memoized(): (P) -> R = Memoizer.memoize<P, R>(this)