Discounted.scala

Discounted.scala

trait Discounted[T] {
  def getDiscount: Double
}
object Discounted {
  // apply method called by compiler to instantiate if no instance found
  def apply[T](implicit discounted: Discounted[T]) = discounted

  def createDiscounted[T](fn: () => Double) = new Discounted[T] {
    override def getDiscount: Double = fn()
  }

  //implicit instances of Discounted for each Membership Card
  implicit val silverCardDiscounted: Discounted[Silver] = createDiscounted( () => 0.0)
  implicit val goldCardDiscounted: Discounted[Gold] = createDiscounted(() => 10.0)
  implicit val platinumCardDiscounted: Discounted[Platinum] = createDiscounted(() => 15.0)
}