Re: How modify numbers in a region by a multiplier?

[Andreas Politz]

Seweryn Kokot <sewkokot@gmail.com> writes:

> Juanma Barranquero <lekktu <at> gmail.com> writes:
>
>> Qiang Guo is right, though, in pointing that you're using a fixed
>> `end' but the buffer or region length is potentially changing with
>> every replace.
>
> Is there a canonical solution to this problem, since it seems that it should
> happen frequently when using the following structure: 
> (while (re-search-forward "\\([0-9.]+\\)" end t)
> (replace-match (format "%.2f" (* (string-to-number (match-string 1))
> multiplier))))
>

Yes, use a marker.

(defun my-multiply-numbers-in-region-or-buffer (multiplier beg end)
  (interactive
   (cons (read-number "Specify a multiplier: " 0.001)
         (if (use-region-p) (list (region-beginning) (region-end))
           (list (point-min) (point-max)))))
  (goto-char beg)
  (let ((end (copy-marker end)))
    (while (re-search-forward "\\([0-9.]+\\)" end t)
      (replace-match (format "%.2f"
                             (* (string-to-number (match-string 1))
                                multiplier)))))
  (when (interactive-p)
    (message "Numbers in %s modified by multiplier %s."
             (if (use-region-p) "region" "buffer")
             multiplier)))


-ap