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From: Ted Zlatanov <tzz@lifelogs.com>
To: emacs-devel@gnu.org
Subject: Re: can `shuffle-vector' be moved?
Date: Fri, 13 May 2011 09:38:59 -0500	[thread overview]
Message-ID: <87ei42y8ak.fsf@lifelogs.com> (raw)
In-Reply-To: jwvei427lcy.fsf-monnier+emacs@gnu.org

On Fri, 13 May 2011 11:00:10 -0300 Stefan Monnier <monnier@iro.umontreal.ca> wrote: 

>>> (loop
>>> for i from (1-  (length vector)) downto 1
>>> do (rotatef (aref vector i) (aref vector (random i)))))

>> Why is this limited to vectors? with elt it could work also with lists.

SM> Its algorithmic performance on lists would be poor (O(N²)).
SM> You want a different algorithm for lists.

I think the performance would not be bad if the list was put into a
vector, shuffled, then put back--just O(N) with twice the memory usage.
That could be a wrapper around the vector shuffle so it can handle
general sequences.

Ted




  reply	other threads:[~2011-05-13 14:38 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-12 19:58 can `shuffle-vector' be moved? Ted Zlatanov
2011-05-13  2:03 ` Leo
2011-05-13  2:10   ` Stefan Monnier
2011-05-13  3:49     ` Ted Zlatanov
2011-05-13 13:57       ` Stefan Monnier
2011-05-13  3:53   ` Ted Zlatanov
2011-05-13  6:00     ` Kevin Rodgers
2011-05-13 14:48       ` Ted Zlatanov
2011-05-13 15:26         ` Stefan Monnier
2011-05-13 16:22           ` Ted Zlatanov
2011-05-13 16:47             ` Stefan Monnier
2011-05-13 16:51               ` Ted Zlatanov
2011-05-13  6:19 ` Thierry Volpiatto
2011-05-13 14:00   ` Stefan Monnier
2011-05-13 14:38     ` Ted Zlatanov [this message]
2011-05-13 17:13     ` Thierry Volpiatto

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