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: def get[S]: State[S, S] = State(s => (s, s)) def set[S](s: S): State[S, Unit] = State(_ => (s, ())) given stateMonad[S]: Monad[[a] =>> State[S, a]] with def pure[A](a: A): State[S, A] = State(s => (s, a)) extension [A](fa: State[S, A]) def flatMap[B](f: A => State[S, B]): State[S, B] = State(s => val (s1, a) = fa.run(s) f(a).run(s1) )