GNU bug report logs - #67456
[PATCH] seq.el: Add functions for mapping over subsequences

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Okamsn <okamsn <at> protonmail.com>
Subject: bug#67456: closed (Re: bug#67456: [PATCH] seq.el: Add functions
 for mapping over subsequences)
Date: Tue, 25 Feb 2025 02:40:02 +0000

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Your bug report

#67456: [PATCH] seq.el: Add functions for mapping over subsequences

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 67456 <at> debbugs.gnu.org.

-- 
67456: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=67456
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Stefan Kangas <stefankangas <at> gmail.com>
To: Okamsn <okamsn <at> protonmail.com>
Cc: nicolas <at> petton.fr, arstoffel <at> gmail.com, 67456-done <at> debbugs.gnu.org
Subject: Re: bug#67456: [PATCH] seq.el: Add functions for mapping over
 subsequences
Date: Mon, 24 Feb 2025 20:39:31 -0600

Okamsn <okamsn <at> protonmail.com> writes:

> Stefan Kangas wrote:
>> Okamsn <okamsn <at> protonmail.com> writes:
>>
>>> Augusto Stoffel wrote:
>>>> This operation has quadratic complexity for anything other than regular
>>>> linked lists.  I'm not sure it's a good idea to add it to a generic
>>>> sequence library...
>>>
>>>
>>> Thank you for the feedback.
>>>
>>> Do you know whether there is a better way to implement the idea for
>>> arrays? Is there a way to apply a function to a portion of the array
>>> without copying the sub-sequences, if that is what you mean?
>>
>> Hmm, it seems like this issue got stuck due to problems with algorithmic
>> complexity.  Performance is a real issue in seq.el, so I think we should
>> solve that before we consider installing anything.
>>
>> Are you still working on this?
>
> I am no longer working on this.  For some things, I opted to use the
> Stream package from ELPA, which now better supports arrays.  Although it
> has the same problem when first traversing a seq.el sequence, it avoids
> recreating things for the sub-sequence.
>
> I am fine with this bug being closed.

Thanks, I guess that means that it's unlikely that we'll make more
progress here.  I'm therefore closing this bug report.

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From: Okamsn <okamsn <at> protonmail.com>
To: bug-gnu-emacs <at> gnu.org, Nicolas Petton <nicolas <at> petton.fr>
Subject: [PATCH] seq.el: Add functions for mapping over subsequences
Date: Sun, 26 Nov 2023 17:17:35 +0000

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Hello,

The attached features work like `cl-maplist` and `cl-mapl`, applying 
functions to a sequence and to the remaining parts of a sequence.  For 
example, `(seq-mapsub #'identity [1 2 3])` returns `([1 2 3] [2 3] [3])`.

The patch adds a `seq-mapsub`, `seq-dosub`, and a `seq-doseqsub`, 
similar to `seq-map`, `seq-do`, and `seq-doseq`, respectively.

I was looking for an equivalent for vectors of `cl-maplist`, `cl-mapl`, 
and `cl-loop`'s `for VAR on LIST`, and think that these would be useful 
additions.

To get the sub-sequences, the code uses `seq-rest` and stops when the 
returned sub-sequence is empty according to `seq-empty-p`.  This is 
similar to how I would do it for a list, using `cdr` and `null`, but is 
that a good way to do it for arrays and other sequences?

Thank you.

[0001-Create-seq-functions-for-mapping-over-subsequences.patch (text/x-patch, attachment)]

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