Re: (copy-marker nil)

[Andreas Röhler]

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.