=> (defn lazy-shuffle [v]
(lazy-seq
(if (seq v)
(let [idx (rand-int (count v))]
(cons (nth v idx)
(lazy-shuffle (pop (assoc v idx (peek v)))))))))
=> (take 10 (lazy-shuffle (vec (range 100))))
(77 63 37 99 81 73 25 85 35 10)
On Fri, Aug 23, 2013 at 10:57 AM, NeedMoreDesu <d...@horishniy.org.ua>wrote:
> (letfn [(vec-throw-out [v i]
> (pop (assoc v i (get v (dec (count v))))))]
> (defn lazy-shuffle [v]
> (if (seq v)
> (let [idx (rand-int (count v))]
> (cons
> (get v idx)
> (lazy-seq
> (lazy-shuffle
> (vec-throw-out v idx))))))))
>
> (let [s (range 1000000)
> v (vec s)]
> (time (take 10 (lazy-shuffle v)))
> nil)
> ;; "Elapsed time: 0.092389 msecs"
>
>
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