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trait Functor[T, F[_]] { self: F[T] =>
def map[K](fn: T => K): F[K]
}
sealed trait Optional[+T] extends Functor[T, Optional]
case class Maybe[T](value:T) extends Optional[T] {
override def map[K](fn: T => K) = Maybe(fn(value))
}
case object Nope extends Optional[Nothing] {
override def map[K](fn: _ => K) = Nope
}
//Well we typedef another type call it X and use it as param here (Bit ugly syntax).
case class Tuple2[A, B](first: A, second: B) extends Functor[B, ({type X[D] =Tuple2[A,D]})#X] {
override def map[C](fn: B => C): Tuple2[A, C] = Tuple2(first, fn(second))
}
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