package Main

object Twice {

  def apply(x: Int): Int = x * 2

  def unapply(z: Int): Option[Int] = if (z % 2 == 0) Some(z / 2) else None

}

object TwiceTest extends App {

  val x = Twice(10)

  x match { case Twice(n) => Console.println(n) } //prints 21

}