yoneda2.scala

abstract class LazyFunctor[F[_], A] { self =>
  // should be implemented as a composition of transformations
  def transformation[B](f: A => B): F[B]
  
  // apply transformations and get our value back
  def run: F[A] = transformation(identity)
  
  // interace 'map' to be used as functor
  def map[B](f: A => B): LazyFunctor[F, B] = new LazyFunctor[F, B] {
    def transformation[C](g: B => C): F[C] = self.transformation(g compose f)
  } 
}