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

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Message #11 received at 18837 <at> debbugs.gnu.org (full text, mbox):

From: Keith David Bershatsky <esq <at> lawlist.com>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 18837 <at> debbugs.gnu.org
Subject: Re: bug#18837: 25.0.50;
 `sort` -- modify function to preserve original list.
Date: Sat, 25 Oct 2014 22:04:55 -0700

Thank you, Stefan, for taking a look at this Emacs report (#18837).

Here is my workaround:

    (defun lawlist-sort (seq predicate)
      (let ((disposable-list (copy-list seq)))
        (sort disposable-list predicate)))

There may be situations where `copy-list` might not work, but that is beyond my present level of understanding / knowledge.  I suppose that there might be some time consumption issues involved with the function `copy-list` for extremely complex lists, but none of my lists would ever get so large/complex that this would be an issue.

Thanks,

Keith

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At Sat, 25 Oct 2014 22:44:45 -0400,
Stefan Monnier wrote:
> 
> > 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.
> 
> 
>         Stefan

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