1 package Main

     2 

     3 object Twice {

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

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

     6 }

     7 

     8 object TwiceTest extends App {

     9   val x = Twice(10)

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

    11 }