[Small-cl-src] shuffle-vector

[Gary King]

I like having both destructive and non-destructive versions:

(defun shuffle-vector (v)
   "Return copy of vector with elements shuffled like a deck of cards."
   (shuffle-vector! (copy-seq v)))

(defun shuffle-vector! (result)
   "Destructively shuffle elements in a vector like a deck of cards."
   (loop
     finally (return result)
     for i from (length result) downto 1
     as j = (random i)
     do (rotatef (svref result j) (svref result (1- i)))))

On Jun 24, 2004, at 10:03 AM, Ben Hyde wrote:

>
> (defun shuffle-vector (v)
>   "Return copy of vector with elements shuffled like a deck of cards."
>   (loop
>     with result = (copy-seq v)
>     finally (return result)
>     for i from (length v) downto 1
>     as j = (random i)
>     do (rotatef (svref result j) (svref result (1- i)))))
>
>
> That was fun.
>
>
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-- 
Gary Warren King, Lab Manager
EKSL East, University of Massachusetts * 413 577 0176

I believe that we can effectively defend ourselves abroad and at home 
without dimming our principles. Indeed, I believe that our success in 
defending ourselves depends precisely on not giving up what we stand 
for.
   -- Al Gore

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