message-based continuation pattern

continuation.scala

import akka.actor.ActorDSL._

case object Work
case object StopIt

implicit val system = akka.actor.ActorSystem()

actor(new Act {
  case class ToDo(items: Int, client: ActorRef, v: Double)
  become {
    case Work => self ! ToDo(100, sender, 0d)
    case ToDo(0, client, result) =>
      // finished
      client ! result
    case ToDo(x, client, intermediateValue) =>
      // do 1% of the work; pretend that this is costly
      val nextValue = (intermediateValue + 0.1) * 2
      self ! ToDo(x - 1, client, nextValue)
    case StopIt => context stop self
  }
})