Repr

gistfile1.scala

  trait CurrencyLike[Repr <: CurrencyLike[Repr]]{
    val value : Double

    def make(d:Double) : Repr
    def +(x: Repr) = make(x.value + value)
  }

  class USD(val value: Double) extends CurrencyLike[USD] { def make(d: Double) = new USD(d) }
  class EUR(val value: Double) extends CurrencyLike[EUR] { def make(d: Double) = new EUR(d) }

  def plus[T <: CurrencyLike[T]](c1: T,  c2:T) : T = c1 + c2