bug#20732: in-string-p fails

[Andreas Röhler]

Am 04.06.2015 um 23:06 schrieb Dmitry Gutov:
> On 06/04/2015 02:50 PM, Andreas Röhler wrote:
>
> > In question slow is better than false.
>
> Then (setq open-paren-in-column-0-is-defun-start nil) in your Emacs 
> config.
>
> > There is no way to know reliably if inside a string than scanning the
> > whole buffer. All other is woodoo.
>
> There's a whole package dedicated to doing is faster and in easier 
> fashion: lisp/emacs-lisp/syntax.el.
>
> You're welcome to suggest improvements that don't sacrifice 
> performance to this extent.

Why not have two functions dealing with different circumstances.

- in-string-p-maybe, which might guess first and fast, re-fine afterwards.

- a precise in-string-p running parse-partial-sexp on widened buffer.

(defun in-string-p-precise ()
  "Returns the character which delimits the string if inside, nil 
otherwise. "
  (save-restriction
    (widen)
    (ignore-errors (nth 3 (parse-partial-sexp (point-min) (point))))))

Maybe also return t if at string-start pos already:

(eq (char-syntax (char-after)) 34)

When not called from complex environment (also precise):

(defun ar-in-string-p ()
  "Return position, if inside or at opening delimiter.

Otherwise return nil. "
  (interactive)
  (save-restriction
    (widen)
    (let* ((pps (parse-partial-sexp (point-min) (point)))
       (erg (and (nth 3 pps) (nth 8 pps)))
       (la (unless erg (when (eq (char-syntax (char-after)) 34)
                 (point)))))
      (setq erg (or erg la))
      (when (interactive-p) (message "%s" erg))
      erg)))