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The weblog of Tony Morris


Posted on November 30, 2008, in Programming

An exercise arising from an IRC discussion in #scala:

    trait Functor[F[_]] {
      def fmap[A, B](fa: F[A], f: A => B): F[B]
    trait Monad[M[_]] {
      def bind[A, B](ma: M[A], f: A => M[B]): M[B]
      def pure[A](a: A): M[A]
    object ObserveFunctorMonad {
      def observe[K[_]](m: Monad[K]): Functor[K] = error("your homework")