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Re: Did the sort do anything?

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On 11/7/2011 4:27 AM, Roedy Green wrote:
> What is the easiest way to determine if a sort actually changed the
> order?
>
> I run into this in two situations.
>
> 1. do I really need to sort in cases when  the data are most likely
> already in order? (perhaps just sorting is as fast as trying to bypass
> it most of the time).
>
> 2. did the sort change anything. Do I have to commit the changed order
> to disk?
>
> The obvious solution to (1) is to pairwise compare array exported from
> the collection before the sort.
>
> The obvious solution to (2) is compare corresponding elements in
> arrays exported before and after the sort with the comparator, or use
> (1).
>
> Can you do better than that?

For Q1: no - I don't think so.

For Q2: yes(*) - use your own sort that returns a boolean
indication whether it changed or not.

* = assuming that you context justifies doing something special - that
is not a given.

Arne

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Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-07 01:27 -0800
  Re: Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-07 02:20 -0800
    Re: Did the sort do anything? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-11-07 11:21 +0000
  Re: Did the sort do anything? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-11-07 10:49 +0000
    Re: Did the sort do anything? Roedy Green <see_website@mindprod.com.invalid> - 2011-11-07 02:58 -0800
  Re: Did the sort do anything? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-07 07:11 -0500
    Re: Did the sort do anything? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-11-07 08:30 -0600
      Re: Did the sort do anything? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-07 21:03 -0500
  Re: Did the sort do anything? markspace <-@.> - 2011-11-07 07:48 -0800
  Re: Did the sort do anything? dagon@dagon.net (Dagon) - 2011-11-07 12:50 -0800
    Re: Did the sort do anything? Cindy <c.thurston@frell.okb.uwa.edu> - 2011-11-07 22:02 -0500
      Re: Did the sort do anything? Cindy <c.thurston@frell.okb.uwa.edu> - 2011-11-07 22:22 -0500
  Re: Did the sort do anything? Arne Vajhøj <arne@vajhoej.dk> - 2011-11-07 17:42 -0500

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