From: "Pascal J. Bourguignon" <pjb@informatimago.com>
To: help-gnu-emacs@gnu.org
Subject: Re: random predicate function
Date: Mon, 13 Dec 2010 19:38:19 +0100 [thread overview]
Message-ID: <87y67tplgk.fsf@kuiper.lan.informatimago.com> (raw)
In-Reply-To: mailman.2.1292264248.1009.help-gnu-emacs@gnu.org
Tyler Smith <tyler.smith@eku.edu> writes:
> "Pascal J. Bourguignon" <pjb@informatimago.com> writes:
>
>>
>> You shoud not use sort to randomize, because it's suboptimal
>> [ O(n*log(n)) at best instead of O(n) ].
>>
>> And foremost, you should not use a predicate that is not a total order
>> because this usually gives invalid results.
>
> I don't know what a 'total order' means. Is the result of the predicate
> invalid or the actual sorting?
http://en.wikipedia.org/wiki/Total_order
Actually, it should even be a strict total order, that is, it must be a <
operator, not a <= operator.
If you have cycles such as: a < b < a
then some sort algorithms may not terminate.
When sorting lists, some algorithms could truncate the result.
--
__Pascal Bourguignon__ http://www.informatimago.com/
A bad day in () is better than a good day in {}.
next prev parent reply other threads:[~2010-12-13 18:38 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.0.1292251427.11097.help-gnu-emacs@gnu.org>
2010-12-13 15:26 ` random predicate function Pascal J. Bourguignon
2010-12-13 17:16 ` Ted Zlatanov
2010-12-13 17:48 ` Pascal J. Bourguignon
2010-12-15 14:51 ` Ted Zlatanov
2010-12-15 15:20 ` Pascal J. Bourguignon
2010-12-15 16:44 ` Ted Zlatanov
2010-12-15 17:28 ` Pascal J. Bourguignon
2010-12-15 18:39 ` Ted Zlatanov
2010-12-15 18:04 ` Drew Adams
2010-12-13 18:17 ` Tyler Smith
[not found] ` <mailman.2.1292264248.1009.help-gnu-emacs@gnu.org>
2010-12-13 18:38 ` Pascal J. Bourguignon [this message]
2010-12-13 19:05 ` Tyler Smith
2010-12-13 14:43 Tyler Smith
2010-12-13 15:37 ` Gary
2010-12-13 16:08 ` Tyler Smith
2010-12-13 16:16 ` Erik Iverson
2010-12-13 16:50 ` Tyler Smith
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