resumption monad

gistfile1.scala

object ResumptionMonad extends App {
  sealed abstract class Resumption[A] {
    def map[B](k: A => B) = flatMap(k andThen Val.apply)
    def flatMap[B](k: A => Resumption[B]): Resumption[B] = {
      def loop(x: Resumption[A]): Resumption[B] =
        x match {
          case Val(value) => k(value)
          case Wrap(value) => Wrap(loop(value))
        }
      loop(this)
    }
  }
  case class Val[A](value: A) extends Resumption[A]
  case class Wrap[A](value: Resumption[A]) extends Resumption[A]

  val Wrap(Wrap(Wrap(Val(a)))) = for {
    x <- Wrap(Wrap(Val(1)))
    y <- Wrap(Val(2))
  } yield x + y

  println(a)
}