ExtendingGivens.scala

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

trait Applicative[F[_]] extends Functor[F]:
  def pure[A](a:A):F[A]

object Lists:
  given Functor[List] with
    def fmap[A,B](fa:List[A])(f:A=>B):List[B] = fa.map(f)
  
  given (using fn:Functor[List]):Applicative[List] with
    def fmap[A,B](fa:List[A])(f:A=>B):List[B] = fn.fmap(fa)(f)
    def pure[A](a:A) = List(a)

This appears to work, but looks wierd:

given Functor[List] with Applicative[List] with
  def fmap[A,B](fa:List[A])(f:A=>B):List[B] = fa.map(f)
  def pure[A](a:A):List[A] = List(a)