Functor / implicit conversion

gistfile1.scala

package functional

trait Functor[F[_]] {
  def fmap[A, B](fa: F[A])(f: A => B): F[B]
}

final class FunctorOps[F[_], A](val self: F[A])(implicit val F: Functor[F]) {
  final def fmap[B](f: A => B) = F.fmap(self)(f)
}

trait FunctorInstances {
  //implicit def OptionFunctor[A] : Functor[Option] = new Functor ...

  implicit def Function1Functor[A1]: Functor[({ type L[A] = A1 => A })#L] =
    new Functor[({ type L[A] = A1 => A })#L] {
      def fmap[A, B](fa: A1 => A)(f: A => B): A1 => B = f compose fa
    }
}

object functor extends FunctorInstances {

  implicit def toFunctorOps[F[_], A](fa: F[A])(implicit F: Functor[F]): FunctorOps[F, A] =
    new FunctorOps(fa)(F)

  implicit def toFunctionFunctionOps = ???

}

object Main extends App {
  import functor._

  val f1 = { x: Int => x.toString() }
  val res1 = Function1Functor.fmap(f1) { _ => 3.0 }
}