ex4 - https://medium.com/@lu4nm3/monad-transformers-vs-mtl-d3a1167e2649

ex4_mvm.scala

def createMonadReader[E](value: E): IO[MonadReader[IO, E]] = {
  for {
    input <- Ref.of[IO, E](value)
  } yield new MonadReader[IO, E] {
    val monad: Monad[IO] = Monad[IO]
    def ask: IO[E] = input.get
    def reader[A](f: E => IO[A]): IO[A] = ask.flatMap(f)
  }
}