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bug#1406: backward-up-list reports scan error incorrectly?
From: |
Alan Mackenzie |
Subject: |
bug#1406: backward-up-list reports scan error incorrectly? |
Date: |
Sat, 22 Nov 2008 14:04:46 +0000 |
User-agent: |
Mutt/1.5.9i |
Hi, Xah!
On Sat, Nov 22, 2008 at 05:01:10AM -0800, xah lee wrote:
> i was able to duplicate your error. Some of my testing in previous
> post went wrong because i was in text-mode.
> though, isn't this something easy to fix?
No, because it isn't a bug. It's the way the function is meant to work.
If there is a bug, it's that the doc-string (and maybe the elisp manual,
I haven't looked) is vague and incomplete.
It seems that you really want a slightly different function.
> I mean, it surely is easy to determine if cursor is in inside double
> quotes, therefore it can simply move out the quote then do
> backward-up-list?
Well, it's easy, but very slow. You first have to define what "inside"
and "outside" mean.
For example, you might scan from BOB, and point is inside a string if
there've been an odd number of string-quotes up to now (taking comments,
etc. into account).
Emacs Lisp Mode defines "inside a string" as an odd number of
string-quotes since the last "(" in column-0. Try going into a large
Elisp file and deleting one of the "s. It throws the fontification out
for the rest of the function, but then "recovers" for the rest of the
file.
> In any case, thanks.
You're welcome!
> Xah
> ??? http://xahlee.org/
--
Alan Mackenzie (Nuremberg, Germany).
> On Nov 22, 2008, at 4:53 AM, xah lee wrote:
> hi Alan,
> >(defun foo (arg)
> > "foo does nothing."
> > (interactive "P"))
> >Put point inside "P", and do C-M-u `backward-up-list'. You get the
> >error.
> (defun foo (arg)
> "foo does nothing. ("
> (interactive "P"))
> , and do the same again. It finds that paren. Why? Because
> backward-up-list assumes its starting point is NOT in a string. It
> jumps backwards over (what it thinks is) the string
> "\n(interactive "
> , and then finds the ?\(.
> This is exactly what is happening in your somewhat larger example.
> In text mode, presumably the syntax table doesn't define ?\" as a string
> quote. In fundamental mode, presumably it does. "(syntax-after
> (point))" is your friend here.