Re-implement Clojure "comp" for 4Clojure problem #58

komp.clj

(ns clojure4.core)
;;; Re-implement Clojure "comp" for 4Clojure problem #58  (as "komp")

(defn komp 
  ([] (fn [n] (identity n)))
  ([fn1] (fn [& n] (apply fn1 n)) )
  ([fn1 fn2] (fn [& n]
               (fn1 ((fn [m] (apply fn2 m)) n))))
  ([fn1 fn2 & fns] (fn [& n]
               (fn1 ((fn [m] (apply (apply komp (conj fns fn2))  m )) n    )))))

;;; tests
((komp inc inc) 0)
((komp dec + inc ) 0)
((komp inc inc inc inc inc ) 0)
  
(= true ((komp zero? #(mod % 8) +) 3 5 7 9))
(= "HELLO" ((komp #(.toUpperCase %) #(apply str %) take) 5 "hello world"))

((komp inc (partial * 2) ) 7)
((komp rest reverse) [1 2 3 4])


;;; Examples from Closuredocs.org comp page 

(def negative-quotient (komp - /))
;; #'user/negative-quotient

(negative-quotient 8 3)  ;;=> -8/3

(def concat-and-reverse (komp (partial apply str) reverse str)) 
;; #'user/concat-and-reverse

(concat-and-reverse "hello" "clojuredocs")
;;=> "scoderujolcolleh"

((komp str +) 8 8 8)   ;;=> "24"

(map
   (komp - (partial + 3) (partial * 2))
       [1 2 3 4])
;;=>  (-5 -7 -9 -11)

(filter (komp not zero?) [0 1 0 2 0 3 0 4])
;;=> (1 2 3 4)

(def countif (komp count filter))
#'user/countif

(countif even? [2 3 1 5 4])
;;=> 2

( (komp second reverse) '("a" 2 7 "b"))   
;;=> 7

( #((apply komp first (repeat %2 rest)) %1) [1 2 3 4 5 6] 3 ) 
;;=> 4