* bug#18837: 25.0.50; `sort` -- modify function to preserve original list.
@ 2014-10-25 21:03 Keith David Bershatsky
2014-10-26 2:44 ` Stefan Monnier
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Keith David Bershatsky @ 2014-10-25 21:03 UTC (permalink / raw)
To: 18837
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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^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#18837: 25.0.50; `sort` -- modify function to preserve original list.
2014-10-25 21:03 bug#18837: 25.0.50; `sort` -- modify function to preserve original list Keith David Bershatsky
@ 2014-10-26 2:44 ` Stefan Monnier
2014-10-26 5:04 ` Keith David Bershatsky
2019-09-16 5:30 ` Stefan Kangas
2 siblings, 0 replies; 4+ messages in thread
From: Stefan Monnier @ 2014-10-26 2:44 UTC (permalink / raw)
To: Keith David Bershatsky; +Cc: 18837
> 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
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#18837: 25.0.50; `sort` -- modify function to preserve original list.
2014-10-25 21:03 bug#18837: 25.0.50; `sort` -- modify function to preserve original list Keith David Bershatsky
2014-10-26 2:44 ` Stefan Monnier
@ 2014-10-26 5:04 ` Keith David Bershatsky
2019-09-16 5:30 ` Stefan Kangas
2 siblings, 0 replies; 4+ messages in thread
From: Keith David Bershatsky @ 2014-10-26 5:04 UTC (permalink / raw)
To: Stefan Monnier; +Cc: 18837
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
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#18837: 25.0.50; `sort` -- modify function to preserve original list.
2014-10-25 21:03 bug#18837: 25.0.50; `sort` -- modify function to preserve original list Keith David Bershatsky
2014-10-26 2:44 ` Stefan Monnier
2014-10-26 5:04 ` Keith David Bershatsky
@ 2019-09-16 5:30 ` Stefan Kangas
2 siblings, 0 replies; 4+ messages in thread
From: Stefan Kangas @ 2019-09-16 5:30 UTC (permalink / raw)
To: Stefan Monnier; +Cc: 18837-done, Keith David Bershatsky
Stefan Monnier <monnier@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
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-09-16 5:30 UTC | newest]
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2014-10-25 21:03 bug#18837: 25.0.50; `sort` -- modify function to preserve original list Keith David Bershatsky
2014-10-26 2:44 ` Stefan Monnier
2014-10-26 5:04 ` Keith David Bershatsky
2019-09-16 5:30 ` Stefan Kangas
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