GNU bug report logs - #18837
25.0.50; `sort` -- modify function to preserve original list.

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Keith David Bershatsky <esq <at> lawlist.com>
Subject: bug#18837: closed (Re: bug#18837: 25.0.50; `sort` -- modify
 function to preserve original list.)
Date: Mon, 16 Sep 2019 05:31:02 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#18837: 25.0.50; `sort` -- modify function to preserve original list.

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 18837 <at> debbugs.gnu.org.

-- 
18837: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18837
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

[Message part 2 (message/rfc822, inline)]

From: Stefan Kangas <stefan <at> marxist.se>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 18837-done <at> debbugs.gnu.org, Keith David Bershatsky <esq <at> lawlist.com>
Subject: Re: bug#18837: 25.0.50; `sort` -- modify function to preserve
 original list.
Date: Mon, 16 Sep 2019 07:30:36 +0200

Stefan Monnier <monnier <at> iro.umontreal.ca> writes:

>> The doc-string for the function `sort` states that `SEQ is modified by
>> side effects`; however, it does not state in what way the original
>> list gets modified or why such a feature might somehow be useful.
>
> The "usefulness" is to avoid allocating another list in the case where
> the unsorted list won't be used later on anyway.

It doesn't seem like there is anything more to do here, so I'm closing
this bug.

Best regards,
Stefan Kangas

[Message part 3 (message/rfc822, inline)]

From: Keith David Bershatsky <esq <at> lawlist.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.0.50; `sort` -- modify function to preserve original list.
Date: Sat, 25 Oct 2014 14:03:25 -0700

The doc-string for the function `sort` states that `SEQ is modified by side effects`; however, it does not state in what way the original list gets modified or why such a feature might somehow be useful.  I attempted to find out the answer to this question on `superuser.com`, however, the community has expressed an interest in closing the question without offering an explanation on this issue:

http://superuser.com/questions/831608/emacs-sort-usefulness-of-side-effect-modifying-initial-list

In my use case, I want to preserve an initial list that is set to a let-bound variable so that I can use it again elsewhere in the function.  To achieve this objection, I used `copy-list`.

Unless the modified `SEQ` is somehow useful, perhaps it would be appropriate to modify the function `sort` so that it preserves the initial list.

Thanks,

Keith

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In GNU Emacs 25.0.50.1 (x86_64-apple-darwin10.8.0, NS appkit-1038.36 Version 10.6.8 (Build 10K549))
 of 2014-10-01 on MP.local
Repository revision: 117996 dmantipov <at> yandex.ru-20141001132108-zdsxru2390mqyjlu
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