bug#20732: in-string-p fails

["Andreas Röhler" <andreas.roehler@easy-emacs.de>]

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)))