Re: beginning-of-defun (again)

[Alan Mackenzie <acm@muc.de>]

Hello, Andreas.

On Thu, Oct 29, 2015 at 12:24:48PM +0100, Andreas Röhler wrote:
>   Hi guys,

> maybe it's time to have a reasonable default-behavior of 
> beginning-of-defun in Emacs Lisp.

> IMO there is no reason for stuff like

> open-paren-in-column-0-is-defun-start

Unfortunately, there is.  Setting it to nil ensures accurate recognition
of non-nested parens, though this can be slow, sometimes very slow.
Setting it to non-nil makes it fast, but sometimes so inaccurate it
looks like a bug.

> A function resp. top-level-form starts if the beginning of a list is 
> followed by a respective keyword.

Not necessarily: how does Emacs know whether something looking like a
"top-level-form" is actually at the top level or not?  When
open-paren-in-column-0-is-defun-start is non-nil, it need scan no
further back than the first such paren encountered.  When
o-p-i-c-0-i-d-s is nil, it must scan all the way from the beginning of
the file.

> The list of keywords being customizable seems a plus :)

This would not work in all modes.

> Cheers,

> Andreas

-- 
Alan Mackenzie (Nuremberg, Germany).