Re: Emacs: adding 1 to every number made of 2 digits inside a marked region.

[Stephen Berman]

On Thu, 23 Sep 2021 17:00:01 +0800 Hongyi Zhao <hongyi.zhao@gmail.com> wrote:

> On Thu, Sep 23, 2021 at 4:07 PM Stephen Berman <stephen.berman@gmx.net> wrote:
[...]
>> In your first screenshot it looks like point in *scratch* is after the
>> number 30 when you evaluate the while-sexp.  Make sure point is before
>> 34 and then it should work.
>
> Exactly. Thank you for pointing this out. Then I do the following
> testing in the scratch buffer:
>
> some    30
> word    31 *
>
> *  This is the position of point.
>
> M-:
> (while (re-search-backward "[[:digit:]]\\{2\\}" nil t) (let ((x
>  (match-string 0))) (delete-backward-char 2) (insert (format "%d" (1+
>  (string-to-number x))))))
>
> Then I obtained the following in scratch:
>
> ;; This buffer is for
> tex100999897969594939291908988878685848382818079787776757473727170696867666564636261605958575655545352515049484746454443424140393837363534333231
>
> Any hints for this strange result?

Since you're now searching backwards, you need to delete forwards to
retain the position of the numbers and you need to make sure point is in
front of the number that was just incremented before continuing the loop:

(while (re-search-backward "[[:digit:]]\\{2\\}" nil t)
  (let ((x (match-string 0))
        (pt (point)))
    (delete-char 2)
    (insert (format "%d" (1+ (string-to-number x))))
    (goto-char pt)))

Steve Berman