GeneratorActor.scala

import akka.actor._

class FibonacciGenerator extends Actor  {
  import FibonacciGenerator._

  def receive = fib() 

  def fib(a: Long = 0, b: Long = 1): Receive = {
    case Next =>
      val c: Long = a + b
      sender ! c
      context.become(fib(b, c))
  }
}

object FibonacciGenerator {
  case object Next
}

object Main extends App {
  import FibonacciGenerator._
  import ActorDSL._

  implicit val system = ActorSystem("test")
  val fib = system.actorOf(Props[FibonacciGenerator])
  
  actor(new Act {
    whenStarting { fib ! Next }
    become {
      case x: Long if x < 9999999999L => 
        println(x)
        fib ! Next
      case x =>
        println(x)
        println("Bye")  
        system.shutdown
    }
  })
}