First experiment in deriving the state monad from the monad definition

gistfile1.scala

//Check whole project https://github.com/globulon/Scala-Patterns-Experiments

object SM {
  case class State[T, S](f: (S) => (T,S)) {
    def apply(s: S): (T, S) = f(s)
  }

implicit def stateToComprehension[T, S](state: State[T,S]) = new {
  implicit val functor = stateFunctor[S]()
  val monad = stateMonad[S]()

  def map[U](f: T => U) = functor.map(state)(f)

  def flatMap[U](f: T => State[U, S]) = monad.flatMap(state)(f)
}

implicit def stateFunctor[S]() = new Functor[({type λ[α] = State[α,S]})#λ] {
  def map[T, U](source: State[T, S])(f: T => U): State[U, S] = new State[U, S]((s: S) => {
    val (value, state) = source(s)
    (f(value), state)
  })
}

implicit def stateMonad[S]() =  new Monad[({type λ[α] = State[α,S]})#λ]{

    def apply[T](data: T) = new State((s: S) => (data, s))

    def flatten[T](m: State[State[T, S], S]): State[T, S] = new State[T, S]((s: S) => {
      val (mp, sp) = m(s)
      mp(sp)
    })
  }
}

 val resultp = for {
      _ <- pushP(3)
      _ <- pushP(5)
      _ <- pushP(7)
      _ <- pushP(9)
      _ <- popP

    } yield ()

    println(resultp(List(1))._2)