Scala await implementation re: http://blog.ometer.com/2011/11/13/task-dispatch-and-nonblocking-io-in-scala/

BlockingDemo.scala

package await

import java.util.concurrent.Callable
import java.util.concurrent.Executors

object BlockingDemo extends App {

  val execSvc = Executors.newSingleThreadExecutor()
  val worker = new MeaningOfLife()

  var future = execSvc.submit(worker)
  println("Thinking...")
  println("The meaning of life is " + future.get())
  println("All done!")
  execSvc.shutdown()
}

NonblockingDemo.scala

package await

import java.util.concurrent.Callable
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors

import scala.util.continuations._

import await.Await.pimpWorker

object NonblockingDemo extends App {

  implicit val execSvc = Executors.newSingleThreadExecutor()
  val worker = new MeaningOfLife()

  println("Thinking...")
  reset(println("The meaning of life is " + worker.await()))
  println("All done!")
  execSvc.shutdown()
}

object Await {
  implicit def pimpWorker[A](callable: Callable[A])(implicit execSvc: ExecutorService): Await[A] = new Await(callable, execSvc)
}

class Await[A](callable: Callable[A], execSvc: ExecutorService) {
  def await(): A @suspendable = shift { k: (A => Unit) =>
    val worker = new AwaitWorker(callable, k)
    execSvc.submit(worker)
  }
}

class AwaitWorker[A](callable: Callable[A], k: A => Unit) extends Callable[Unit] {
  def call(): Unit = k(callable.call())
}

Worker.scala

package await

import java.util.concurrent.Callable

class MeaningOfLife extends Callable[Int] {
  def call(): Int = {
    Thread.sleep(5000)
    42
  }
}