scalameta-tut-naive-1.scala

class CacheBackEnd[K, V] {
  private var map = Map.empty[K, V]     // ignore the fact it is not thread safe
  
  // `compute` is a function, only evaluated in case of cache miss
  def getOrElse(k: K, compute: K => V): V = {
    map.get(k) match {
      case Some(v) => v       // cache hit
      case None =>
        val v = compute(k)
        map = map + (k -> v)
        v
    }
  }
}

def cache[K, V](fn: K => V)(cacheStorage: CacheBackEnd[K, V]): K => V = {
  (k: K) => 
    cacheStorage.getOrElse(k, fn)
}