4clojure problem 44: rotate a sequence

4c_p44.clj

; rotate a sequence 

(fn [index col]
  (letfn [(rotate [index col]
          (nth (iterate #(concat (rest %) (list (first %))) col) index))]
  (if (> index 0) 
      (rotate index col)
      (reverse (rotate (* -1 index) (reverse col))))))


;other solutions: 
;beickhoff's
(fn rotate [n xs]
  (let [length (count xs)
        n* (mod n length)]
    (concat (drop n* xs) (take n* xs))))


;maximental's solution:
(fn [n x]
  (take (count x)
        (drop (mod n (count x))
              (cycle x))))

;malvert's solution:
(fn [n seq]
  (let [k (mod n (count seq))]
    (concat (drop k seq) (take k seq))))

;shockbob's solution:
#(let [ 
       [l r] (split-at (mod % (count %2)) %2)]
    (concat r l))