From: Augusto Stoffel <arstoffel@gmail.com>
To: Philip Kaludercic <philipk@posteo.net>
Cc: "Matúš Goljer" <matus.goljer@gmail.com>, emacs-devel@gnu.org
Subject: Re: [PATCH] seq.el: add seq-last for symmetry with seq-first
Date: Wed, 15 Mar 2023 08:06:20 +0100 [thread overview]
Message-ID: <87mt4ebij7.fsf@gmail.com> (raw)
In-Reply-To: <87edprm1l0.fsf@posteo.net> (Philip Kaludercic's message of "Tue, 14 Mar 2023 22:04:43 +0000")
On Tue, 14 Mar 2023 at 22:04, Philip Kaludercic wrote:
>>> Maybe it's more useful to allow negative arguments in seq-elt? Saying
>>> (seq-elt seq -1) isn't much more effort than (seq-last seq).
>>
>> I'm personally a bit ambiguous about negative indices. It's nice for
>> those one liners when you need them, but they are quite confusing
>> especially if you switch between languages and they all implement them a
>> bit differently.
>
> The only language I am really familiar with is python, and what that
> effectively does is (mod i (length n)), what do other languages do?
In Python "abc"[-4] throws and error. I don't think there's any choice
to be made here: If it were to support a negative index n, then
(seq-elt s n) should just return the (+ (length s) n)-th element, with
the usual treatment for out of bounds indices (whatever it is).
> Another thing that should be kept in mind that sequences can be streams
> (as provided by stream.el), and there doesn't have to be a final
> element.
What is the seq-length of an infinite stream? And does asking for the
length of a stream consume it? If so, then seq is an imperfect
abstraction for streams.
next prev parent reply other threads:[~2023-03-15 7:06 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-14 12:55 [PATCH] seq.el: add seq-last for symmetry with seq-first Matúš Goljer
2023-03-14 15:26 ` Philip Kaludercic
2023-03-14 15:48 ` Matúš Goljer
2023-03-14 16:14 ` Philip Kaludercic
2023-03-14 18:35 ` Augusto Stoffel
2023-03-14 19:14 ` Matúš Goljer
2023-03-14 22:04 ` Philip Kaludercic
2023-03-15 7:06 ` Augusto Stoffel [this message]
2023-03-15 8:09 ` Philip Kaludercic
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