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

[Stephen Berman]

On Thu, 23 Sep 2021 18:13:08 +0800 Hongyi Zhao <hongyi.zhao@gmail.com> wrote:

> On Thu, Sep 23, 2021 at 6:08 PM Stephen Berman <stephen.berman@gmx.net> wrote:
>>
>> 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)))
>
> Tried but it does nothing.

Since you're now searching backwards, are you sure you had point *after*
the numbers?  I.e., if this is the *scratch* buffer:

-------------------------------------------------------
;; some    35
;; word    31
;; another 39
;; thing   60
;; to      40
;; say     11
;; here    48

(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)))
-------------------------------------------------------

then put the cursor at the end of the sexp and type `C-x C-e'.

Steve Berman