Re: master 4b79c80c999 1/2: New function 'sort-on'

[Daniel Mendler via "Emacs development discussions." <emacs-devel@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Daniel Mendler <mail@daniel-mendler.de>
>> Cc: emacs-devel@gnu.org
>> Date: Fri, 02 Feb 2024 16:26:58 +0100
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> >> Would this function fit into the seq library, named seq-sort-on?
>> >
>> > "Fit" in what sense?
>> 
>> The function works with other sequence types too and it seems a good
>> idea to collect sequence-related functionality in seq.el.
>
> OK, but the result is always a list, something seq.el doesn't do.

Right. Seq functions usually return sequences of the same type as the
argument type. I've found one exception though: `seq-keep' always
returns lists. Maybe `seq-keep' should be corrected?

I propose to generalize `sort-on' to other sequence types.

>> > This function can only sort lists, so at least from that aspect its
>> > place is not in seq.el.  In addition, I see no reason to have it
>> > preloaded.
>> 
>> No, in the current form, the function works on vectors too. It always
>> returns a list though. But maybe it makes sense to generalize it such
>> that it returns the same type as the argument.
>
> I see no reason to preload this function, anyway.

Agree, this is certainly a reason. However if the function is general
and useful enough, this should not prevent making it part of seq.el.
There have been additions to seq.el in the past. Of course each addition
has to be considered carefully. The same applies to additions to
subr.el.

>> > I've put it in sort.el because the function 'sort' is there.
>> 
>> No, sort is defined in src/fns.c.
>
> And your point is...?

My point is that sort.el is not the ideal place for this function. As
Michael mentioned, sort.el provides commands to sort lines, paragraphs
and other units of text in buffers. In contrast, new `sort-on' function
is a small library function, so it should better be added to subr.el or
subr-x.el, or with a different name to seq.el.

Daniel