scala3-TypeLambdas1.scala

// Adapted from:
// https://github.com/deanwampler/programming-scala-book-code-examples/blob/master/src/main/scala/progscala3/typesystem/typelambdas/Functor.scala

trait Functor[M[_]]:
  extension [A] (m: M[A]) def map2[B](f: A => B): M[B]

given Functor[Seq] with
  extension [A] (seq: Seq[A]) def map2[B](f: A => B): Seq[B] = seq map f

given Functor[Option] with
  extension [A] (opt: Option[A]) def map2[B](f: A => B): Option[B] = opt map f