bug#32743: 27.0.50; down-list RFC

bug#32743: 27.0.50; down-list RFC

[Andreas Röhler]

Hi all,

‘down-list’ currently returns nil if successful but Scan error:
"Containing expression ends prematurely" if no further list exist downwards.

Suggest to return position reached if successful and nil if no further
list exist.

BTW with current or-clause, second expression will be never be
executed due to error thrown as mentioned:

(goto-char (or (scan-lists (point) inc -1) (buffer-end arg)))

Also reaching buffer-end doesn't make sense IMO in this case, point
should not change then while returning nil.

Thanks,
Andreas
gladly running GNU Emacs 27.0.50 (build 1, i686-pc-linux-gnu, GTK+ 
Version 3.14.5) of 2018-09-15

bug#32743: 27.0.50; down-list RFC

[Lars Ingebrigtsen]

Andreas Röhler <andreas.roehler@easy-emacs.de> writes:

> ‘down-list’ currently returns nil if successful but Scan error:
> "Containing expression ends prematurely" if no further list exist downwards.
>
> Suggest to return position reached if successful and nil if no further
> list exist.

Hm...  I'm not sure that makes sense -- this is down-list:

  (let ((inc (if (> arg 0) 1 -1)))
    (while (/= arg 0)
      (goto-char (or (scan-lists (point) inc -1) (buffer-end arg)))
      (setq arg (- arg inc)))))

It very much looks like a command just meant for interactive use, and if
you want to do something programmatically in this area, you should
probably just use scan-lists directly.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no