fibo.clj

(ns fibo)

(defn fibo-rec [n]
  (cond
    (= n 0) 0
    (= n 1) 1
    :else (+ (fibo-rec (- n 1))
             (fibo-rec (- n 2)))))

(defn fibo-tail-rec [n]
  (loop [n n
         [a b] [0 1]]
    (cond
      (= n 0) a
      (= n 1) b
      :else (recur (dec n) [b (+ a b)]))))

(println "(fibo-rec 40) = " (time (fibo-rec 40)))
; (out) "Elapsed time: 2614.9296 msecs"
; (out) (fibo-rec 40) =  102334155
(println "(fibo-tail-rec 40) = " (time (fibo-tail-rec 40)))
; (out) "Elapsed time: 0.057141 msecs"
; (out) (fibo-tail-rec 40) =  102334155