lazy-sequenceって重要ですね＞＜

http://d.hatena.ne.jp/kencoba/20100405/1270433351
速度が全然違う＞＜

(defn move [a b]
  ['move a 'to b])

(defn hanoi [a b c n]
  (if (< n 1)
    nil
    (if (= n 1)
      (list (move a c))
      (concat (hanoi a c b (- n 1))
              (cons (move a c)
                    (hanoi b a c (- n 1)))))))

(defn hanoi-seq [a b c n]
  ((fn step [a b c n]
     (lazy-seq
      (cond (< n 1) nil
	    (= n 1) (list (move a c))
	    :else (lazy-cat (step a c b (- n 1))
			    (list (move a c))
			    (step b a c (- n 1))))))
   a b c n))

(defn h [fun n] (fun 'a 'b 'c n))

(defn check [n]
  (empty?
   (remove identity
	   (map (fn [i] (= (h hanoi i) (h hanoi-seq i)))
		(take n (iterate inc 1))))))

(check 15)  ; => true
(time (do (h hanoi 15) 'end)) ; => "Elapsed time: 5.448703 msecs"end
(time (do (h hanoi-seq 15) 'end)) ; => "Elapsed time: 0.054197 msecs"end

まー、単に評価されていないだけなんですけど

(time (do (dorun (h hanoi 15)) 'end)) ; => "Elapsed time: 61.193063 msecs"end
(time (do (dorun (h hanoi-seq 15)) 'end)) ; => "Elapsed time: 150.73996 msecs"end