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Re: beginning-of-defun (again)


From: Andreas Röhler
Subject: Re: beginning-of-defun (again)
Date: Thu, 29 Oct 2015 13:56:49 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.9) Gecko/20100915 Thunderbird/3.1.4

 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.


  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?

Top-level here is the beginning of a not nested list.
Remains to set the keywords more or less restrictive.

   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.


The default can't work in all modes but be reliable in Emacs Lisp.




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