Factorial computation in clojure

factorials.clj

(defn factorial-using-recur [x]
  (loop [current x
         next (dec current)
         total 1]
    (if (> current 1)
      (recur next (dec next) (* total current))
      total)))

(defn factorial-using-reduce [x]
  (reduce * (range 1 (inc x))))

(defn make-fac-function [n]
  (fn [] (reduce * (range 1 (inc n)))))

; produces a function that will calculate the factorial on demand
(defmacro factorial-using-macro [x]
  `(fn [] (* ~@(range 1 (inc x)))))
;; (macroexpand `(factorial-using-macro 10))
;; => (fn* ([] (clojure.core/* 1 2 3 4 5 6 7 8 9 10)))

(defn factorial-using-cons-and-eval [x]
  (eval (cons '* (range 1 (inc x)))))

(defn factorial-with-apply [x]
  (apply * (range 1 (inc x))))

(assert (== (factorial-using-reduce 5)
             ((make-fac-function 5))
             ((factorial-using-macro 5))
             (factorial-using-recur 5)
             (factorial-using-cons-and-eval 5)
             (factorial-with-apply 5)
             (* 1 2 3 4 5))
  "something broke")