Luhn algorithm checker

luhn.clj

(ns cl1.core)

(defn prod-digits
  [ps]
  (->> ps 
       (map #(reduce * %1)) 
       (map #(cond 
               (> %1 9) (- %1 9) 
               :else %1)) 
       (reduce +)))

(defn split-string-to-letters
  [ss]
  (map (comp #(Integer/parseInt %) str) ss))

(defn luhn?
  "Check Luhn check digit"
  [n]
  (->> n 
       Integer/toString 
       split-string-to-letters
       (map vector (cycle [2 1])) 
       prod-digits 
       (#(mod % 10))
       (= 0) ))