From: "Andreas Röhler" <andreas.roehler@easy-emacs.de>
To: Help Gnu Emacs mailing list <help-gnu-emacs@gnu.org>
Subject: Re: (copy-marker nil)
Date: Mon, 7 May 2018 16:20:41 +0200 [thread overview]
Message-ID: <1e55da6a-d791-c613-ac9a-5d9bc57f840f@easy-emacs.de> (raw)
In-Reply-To: <CAM-tV-9-4ooe1ZwxH1aEUO0Qcka_vC1k5P3MSRvtHJTc0qAn-A@mail.gmail.com>
On 07.05.2018 15:55, Noam Postavsky wrote:
> On 7 May 2018 at 04:19, Andreas Röhler <andreas.roehler@easy-emacs.de> wrote:
>
>> being surprised WRT behavior of copy-marker:
>>
>> (setq a (copy-marker nil)) -> #<marker in no buffer>
>> (markerp a) -> t
>> a -> #<marker in no buffer>
>>
>> Is taking nil by copy-marker reasonable?
>
> For most functions, passing nil for an &optional parameter is the same
> as omitting it.
>
> (copy-marker &optional MARKER TYPE)
> [...]
> If MARKER is not specified, the new marker does not point anywhere.
>
It's about the return value.
A marker pointing nowhere, might it be considered valid?
Expected such returning nil.
The use-case is the end-position of some object at point. Which will not
exist, if there exists no one there. A useful info maybe.
Without marker, the end-position will be nil. However (setq end-position
(copy-marker an-end-maybe)) makes it being something at any case.
next prev parent reply other threads:[~2018-05-07 14:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-07 8:19 (copy-marker nil) Andreas Röhler
2018-05-07 13:39 ` John Mastro
2018-05-07 14:23 ` Andreas Röhler
2018-05-07 13:55 ` Noam Postavsky
2018-05-07 14:20 ` Andreas Röhler [this message]
2018-05-07 14:26 ` Drew Adams
2018-05-07 17:16 ` Andreas Röhler
2018-05-08 1:46 ` Stefan Monnier
2018-05-08 8:44 ` Andreas Röhler
2018-05-12 22:06 ` Stefan Monnier
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