TypelevelPolymorphic.scala

object TypelevelPolymorphic extends App {

  object square extends Poly {
    import scala.language.reflectiveCalls
    implicit val is = at[Int]    { i => i * i }
    implicit val fs = at[Float]  { f => f * f }
    implicit val ds = at[Double] { d => d * d }
  }

  trait Poly {
    def apply[A,B](a: A)(implicit f: Case[A,B]): B = f(a)
    final def at[A] = new {
      def apply[B](f: A => B): Case[A,B] =
        new Case[A,B] {
          def apply(a: A): B = f(a)
        }
    }
  }

  sealed trait Case[A,B] {
    def apply(a: A): B
  }


  import square._

  println(square(4))
  println(square(1.61f))
  println(square(3.14d))
}

Demonstration of polymorphic typelevel programming.
More tricks here: https://vimeo.com/165837504