[racket-dev] How about adding this simple list-shuffling procedure to racket?

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Thu Nov 11 12:31:55 EST 2010

I think that if random doesn't pick the same number twice you're
guaranteed to be independent of the sorting algorithm, at least.


On Thu, Nov 11, 2010 at 11:18 AM, Neil Toronto <neil.toronto at gmail.com> wrote:
> Eric Hanchrow wrote:
>> I find myself using this all the time; it seems it'd be handy to have
>> built in.
>> (define (shuffled list)
>>  (sort list < #:key (lambda (_) (random)) #:cache-keys? #t))
> Is the distribution of shuffled lists uniform? That'd be hard to analyze,
> since it would depend on the sorting algorithm. I would guess it's not.
> (Don't worry if you didn't catch this yourself. It's not exactly
> straightforward.)
> If you want an "unbiased" shuffle, see
>    http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
> Neil T
> _________________________________________________
>  For list-related administrative tasks:
>  http://lists.racket-lang.org/listinfo/dev

Posted on the dev mailing list.