You can certainly find examples of unreadable Haskell, specifically in the vicinity of ivory towers — there must be something in the air up there which makes academics fond of operator line noise. However, compare the following Scala [1]:

    implicit def KleisliCategory[M[_]: Monad]: Category[({type λ[α, β]=Kleisli[M, α, β]})#λ] = new Category[({type λ[α, β]=Kleisli[M, α, β]})#λ] {
      def id[A] = ☆(_ η)
      def compose[X, Y, Z](f: Kleisli[M, Y, Z], g: Kleisli[M, X, Y]) = f <=< g
    }

    newtype Kleisli m a b = Kleisli { runKleisli :: a -> m b }

    instance Monad m => Category (Kleisli m) where
      id = Kleisli return
      (Kleisli f) . (Kleisli g) = Kleisli (\b -> g b >>= f)

[2]: https://github.com/ghc/packages-base/blob/master/Control/Arr...