From: Bastien <bzg@gnu.org>
To: Juanma Barranquero <lekktu@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Why (substring "abc" 0 4) does not return "abc" instead of an error?
Date: Mon, 16 Jul 2012 09:14:00 +0200 [thread overview]
Message-ID: <871ukcmb47.fsf@gnu.org> (raw)
In-Reply-To: <CAAeL0STZCHYtchx4UG9fgTyrpcgPXFuVV=8mgFHzb0ntz3z74w@mail.gmail.com> (Juanma Barranquero's message of "Mon, 16 Jul 2012 02:10:37 +0200")
Juanma Barranquero <lekktu@gmail.com> writes:
> On Mon, Jul 16, 2012 at 1:59 AM, Bastien <bzg@gnu.org> wrote:
>
>> I read (substring "abc" 0 4) as "return the biggest substring
>> between 0 and 4" -- even if the string does not have 4 characters.
>
> "Even if the string does not have 4 characters" is not even suggested
> in substring's doc.
I know -- I was just expressing my spontaneous (and erroneous)
assumption.
>> Surely I misread, but this would be handy in some cases, instead
>> of using something like (format "%.4s" "abc").
>
> Would it be handy? Sometimes, perhaps. At other times, having
> substring check that TO is indeed in range is quite useful.
I would be happy with a third optional argument FAIL-SILENTLY.
> Also, if
> you start with substring, then it will be buffer-substring, and then
> most functions that deal with string ranges, and then buffer ranges?
I get your point and I don't mind a bit of discipline.
Still, `substring' already behaves differently than its cousins
by allowing negative values as arguments. I have a fuzzy feeling
my expectation comes from this peculiarity, but cannot formalize how
> I'm sure use cases could be found for all these functions where your
> expansive interpretation would be handy...
>
> BTW, for unexpected behavior wrt strings, my favourite is this one
> (it's not a bug);
>
> (let ((s "ab") (m 2)) (eq (substring s 0 m) (substring s 0 m))) => nil
> (let ((s "ab") (m 1)) (eq (substring s 0 m) (substring s 0 m))) => nil
> (let ((s "ab") (m 0)) (eq (substring s 0 m) (substring s 0 m))) => t
Well, this boils down to
(eq "a" "a") => nil
(eq "" "") => t
where "" is really nil -- I my brain can swallow easily.
--
Bastien
next prev parent reply other threads:[~2012-07-16 7:14 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-15 23:15 Why (substring "abc" 0 4) does not return "abc" instead of an error? Bastien
2012-07-15 23:29 ` Juanma Barranquero
2012-07-15 23:59 ` Bastien
2012-07-16 0:10 ` Juanma Barranquero
2012-07-16 7:14 ` Bastien [this message]
2012-07-16 16:15 ` Stefan Monnier
2012-07-16 16:22 ` Bastien
2012-07-16 16:46 ` Bastien
2012-07-16 17:57 ` Tassilo Horn
2012-07-16 18:51 ` Lars Magne Ingebrigtsen
2012-07-16 19:30 ` Bastien
2012-07-16 19:30 ` Tassilo Horn
2012-07-16 20:20 ` Pascal J. Bourguignon
2012-07-16 19:25 ` Bastien
2012-07-16 19:43 ` Bastien
2012-07-16 20:19 ` Pascal J. Bourguignon
2012-07-16 20:30 ` Stefan Monnier
2012-07-16 22:28 ` Lennart Borgman
2012-07-16 22:48 ` Bastien
2012-07-16 22:53 ` Lennart Borgman
2012-07-16 7:38 ` Andreas Schwab
2012-07-16 9:40 ` Juanma Barranquero
-- strict thread matches above, loose matches on Subject: below --
2012-07-16 3:45 Dmitry Gutov
2012-07-16 7:32 ` Bastien
2012-07-16 7:52 ` Thierry Volpiatto
2012-07-16 8:38 ` Bastien
2012-07-16 13:03 ` Dmitry Gutov
2012-07-16 14:32 ` Bastien
2012-07-16 13:10 ` Pascal J. Bourguignon
2012-07-16 14:40 ` Bastien
2012-07-16 15:00 ` Pascal J. Bourguignon
2012-07-16 15:07 ` Lennart Borgman
2012-07-16 15:19 ` Pascal J. Bourguignon
2012-07-16 15:22 ` Bastien
2012-07-16 15:46 ` Bastien
2012-07-16 15:49 ` Bastien
2012-07-16 19:49 ` Thien-Thi Nguyen
2012-07-16 22:32 ` Bastien
2012-07-16 15:56 ` Pascal J. Bourguignon
2012-07-16 16:13 ` Bastien
2012-07-16 19:00 Dmitry Gutov
2012-07-16 19:51 ` Tassilo Horn
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