factorial - clojure

gistfile1.clj

(defn factorial[number]
  (letfn [(tail-recursive-factorial[count number]
                                   (if (= number 0)
                                     count
                                     (tail-recursive-factorial (* count number) (- number 1))))]
  (tail-recursive-factorial 1 number)))

(factorial 5)

(defn factorial[number]
  (reduce * (range 1 (+ number 1))))

(factorial 5)

(defn factorial[number]
  (if (= number 0)
    1
    (* number (factorial (- number 1)))))
  
(factorial 5)