package extension.monad

trait Monad[A, M[_]] {
  // >>= :: Monad m => m a -> (a -> m b) -> m b
  def flatMap[B](input: A => M[B]): M[B] // AKA "bind"
}

trait Functor[A, F[_]] {
  // fmap :: Functor f => (a -> b) -> f a -> f b
  def map[B](input: A => B): F[B] // AKA "fmap"
}

object MOption {
  implicit class MonadicOption[A](left: Option[A]) extends Monad[A, Option] with Functor[A, Option] {
    def flatMap[B](right: A => Option[B]): Option[B] = left match {
      case Some(x) => right(x)
      case None => None
    }

    def map[B](right: A => B): Option[B] = left match {
      case Some(x) => Some(right(x))
      case None => None
    }
  }
}