Memoize.scala

import scala.collection.mutable

// largely cribbed from http://stackoverflow.com/q/16257378
object Memoize {

  /**
   * Simple memoizer backed by a mutable hashmap. Probably not thread safe.
   * @param f function to be memoized
   * @tparam K function parameter type
   * @tparam V function return type
   * @return memoized f
   */
  def simple[K, V](f: K => V) = new mutable.HashMap[K, V]() { cache =>
    override def apply(key: K): V = cache.getOrElseUpdate(key, f(key))
  }

  /**
   * mutable.Hashmap-backed memoizer with synchronized access
   * @param f function to be memoized
   * @tparam K function parameter type
   * @tparam V function return type
   * @return memoized f
   */
  def synchronized[K, V](f: K => V) = new mutable.HashMap[K, V]() { cache =>
    override def apply(key: K): V = cache.synchronized {
      cache.getOrElseUpdate(key, f(key))
    }
  }
}