Subject: Re: bug#3416: down-list

From: Andreas Röhler <[email-masked]>
Date: Fri, 29 May 2009 20:04:48 +0200

martin rudalics wrote:
> > you are right. Nonetheless, as strings are common
> > elements of lists, not just in Python, its such an
> > inconvenience, it qualifies as bug in my eyes.
> >
> > If you don't want to dig into scan-list, that trivial
> > line I've sent is enough to cure it.
>
> IIUC you want to skip anything but a left paren before starting the
> scan.  This means you might skip the start of a comment or string and
> end up before the first left paren within that comment or string.
>
> The only right way to do that is to parse the syntax until point first
> and handle the case where you are in a comment or string 

OK, but checking for string seems enough, as we are inside a list.
> appropriately.
> That approach has been suggested a number of times but so far no one has
> implemented it.
>
> martin
>
Very bad, as going down a list is a very basic task for any editor.
This should work:

(defun down-list (&optional arg)
  "Move forward down one level of parentheses.
With ARG, do this that many times.
A negative argument means move backward but still go down a level.
This command assumes point is not in a string or comment."
  (interactive "^p")
  (or arg (setq arg 1))
  (let ((inc (if (> arg 0) 1 -1)))
    (while (/= arg 0)
      ;; 2009-05-29 [email-masked] changed section start     
      (while (or (not (looking-at "\\s(")) (and (looking-at
"\\s(")(in-string-p)))
        (forward-char 1)
        (skip-syntax-forward "^\\s("))
      ;; 2009-05-29 [email-masked] changed section end     
      (goto-char (or (scan-lists (point) inc -1) (buffer-end arg)))
      (setq arg (- arg inc)))))

(defun in-string-p (&optional pos)
  (let ((orig (or pos (point))))
    (save-excursion
      (save-restriction
        (widen)
      (beginning-of-defun)
      (numberp (nth 3 (parse-partial-sexp (point) orig)))))))

Grüße

Andreas