Haskell vs Clojure: function composition — Learn You a Haskell for Great Good!

fn-comp.clj

;; without composition
(repeat 2 (apply * (map #(* 3 %) (map max [1 2] [4 5]))))

;; with composition
((comp (partial repeat 2)
       (partial apply *)
       (partial map (partial * 3)))
 (map max [1 2] [4 5]))

;; with thread macro
(->> (map max [1 2] [4 5])
     (map (partial * 3))
     (apply *)
     (repeat 2))

fn-comp.hs

-- without composition
replicate 2 (product (map (* 3) (zipWith max [1, 2] [4, 5])))

-- with composition
replicate 2 . product . map (* 3) $ zipWith max [1, 2] [4, 5]

The trade-off being that haskell doesn't support multi-arity functions.

Of course, with clojure's macros, you can create new syntax. Something as simple as this:

(defmacro dot-comp
  [& body]
  (->> body
       (partition-by #{'.})
       (remove #{'(.)})
       (apply list '->>)))

let's you write:

(dot-comp map max [1 2] [4 5] . map (partial * 3) . apply * . repeat 2)

I also like that in the clojure example, the operations get applied in left->right order, as opposed to the haskell example's right->left ordering.

Learn you clojure for great good?