gistfile1.scala

trait Pointed[F[_]] {
  def point[A](a: => A): F[A]
}

trait Functor[F[_]] {
  def fmap[A, B](fa: F[A])(f: A => B): F[B] 
}

trait Show[A] {
  def shows(a: => A): String
}

trait OptionPointedInstances {
  implicit def optionPoint: Pointed[Option] = new Pointed[Option] {
    def point[A](a: => A) = Some(a)
  }
}

trait OptionShowInstances extends OptionPointedInstances {
  implicit def optionShow[A]: Show[Option[A]] = new Show[Option[A]] { 
    def shows(a: => Option[A]) = a.toString
  }
}

trait OptionFunctorInstances extends OptionPointedInstances {
  implicit def optionFunctor: Functor[Option] = new Functor[Option] {
    def fmap[A, B](fa: Option[A])(f: A => B) = fa map f
  }
}

object optionShowInstances extends OptionShowInstances
object optionFunctorInstances extends OptionFunctorInstances

object test {
  import optionShowInstances._
  import optionFunctorInstances._
  
  implicitly[Pointed[Option]] // why isn't this ambiguous??
  optionPoint // error: reference to optionPoint is ambiguous. As expected...
}