Re: beginning-of-defun (again)

[Andreas Röhler]

 On 29.10.2015 14:31, David Kastrup wrote:
> Andreas Röhler<address@hidden>  writes:
>
> >   On 29.10.2015 13:46, Alan Mackenzie wrote:
> > > 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,
> > Sorry, Alan, but if there is no syntax expecting a start in column 0,
> > there is no reason to assume that.
> >
> > Relying on such means working in some cases, in other not. You won't
> > want that.
> If Emacs becomes too slow for useful work otherwise, that's no
> alternative to it sometimes making assumptions leading to bad
> highlighting.

Where it was proven Emacs is slow WRT an reasonable implementation, if 
such a thing doesn't exist?
AFAIK the current buggy one predates parse-partial-sexp and that part 
was never reconsidered WRT pps since.

Slow is the current "re-search-backward (if defun-prompt-regexp" stuff, 
which might be replaced by calls to pps + keyword.