andrus

    app : Vect n a -> Vect m a -> Vect (n + m) a

  data EitherIO e a = EitherIO {
      runEitherIO :: IO (Either e a)
  }

  data EitherIO e a = MakeEitherIO {
      runEitherIO :: IO (Either e a)
  }

  IO (Either e a) -> EitherIO e a

  EitherIO e a -> IO (Either e a)