Atoms in Scala

atoms.scala

import java.util.concurrent.atomic.AtomicReference

import scala.annotation.tailrec

class Atom[T <: AnyRef](initialValue: T) {
  private val value = new AtomicReference[T](initialValue)

  def swap(fun: T => T) {
    @tailrec def update(expect: T): Unit =
      if ( !value.compareAndSet(expect, fun(expect)) ) update(value.get)

    update(value.get)
  }

  def apply() = value.get
}

class MapAtom[K,V](initialValue: Map[K,V]) extends Atom(initialValue) {
  
  def update(key: K, value: V) = this.swap(_.updated(key,value))

}

object Main extends App {

  val myAtom = new Atom(Map('foo -> "fooval"))
  myAtom.swap( (old) => old.updated('foo, "foonewval"))
  myAtom.swap(_.updated('foo, "foonewval"))
  println(myAtom())

  val myMapAtom = new MapAtom[Symbol,String](Map('foo -> "fooval"))
  myMapAtom.update('foo,"foonewval")
  println(myMapAtom())
  
}