Fibonacci with Clojure

fibo.clj

; Credit: Programming Clojure http://pragprog.com/book/shcloj/programming-clojure

; Fibonacci infinite sequence
(defn lazy-seq-fibo
  ([]
    (concat [0 1] (lazy-seq-fibo 0N 1N)))
  ([a b]
    (let [n (+ a b)]
      (lazy-seq
        (cons n (lazy-seq-fibo b n))))))

(take 10 (lazy-seq-fibo))
(nth (lazy-seq-fibo) 10000)

; Reusing existing sequence library functions
; (take 5 (iterate (fn [[a b]] [b (+ a b)]) [0N 1N])) -> ([0 1] [1 1] [1 2] [2 3] [3 5])
(defn fibo []
  (map first (iterate (fn [[a b]] [b (+ a b)]) [0N 1N])))

(take 10 (fibo))
(nth (fibo) 10000)
; All fibos (never ends):
(fibo)