package readerwriter.internal /* You don't need to edit any of the files inside this package. These are the actual implementations, and you should * only use the provided methods, not rely on internal structure */ import applicative.Monad case class State[S, A] private (run: S => (S, A)) case object State { implicit def stateMonad[S]: Monad[State[S, ?]] = new Monad[State[S, ?]] { override def unit[A](a: A): State[S, A] = State(s => (s, a)) override def flatMap[A, B](fa: State[S, A])(f: A => State[S, B]): State[S, B] = State(s => { val (s1, a) = fa.run(s) f(a).run(s1) }) } def get[S]: State[S, S] = State(s => (s, s)) def set[S](s: S): State[S, Unit] = State(_ => (s, ())) }