Re: A variant of match-end, but after replacement?

[Marcin Borkowski]

On 2015-07-20, at 00:45, Pascal J. Bourguignon <pjb@informatimago.com> wrote:

> Barry Margolin <barmar@alum.mit.edu> writes:
>
>> In article <mailman.7160.1437335923.904.help-gnu-emacs@gnu.org>,
>>  Marcin Borkowski <mbork@mbork.pl> wrote:
>>
>>> On 2015-07-19, at 15:41, Pascal J. Bourguignon <pjb@informatimago.com> 
>>> wrote:
>>> 
>>> > Marcin Borkowski <mbork@mbork.pl> writes:
>>> >
>>> >>>     (let ((old-end (prog1 (match-end 1)
>>> >>>                      (replace-match "newtext" t t string 1)))) 
>>> >>>        (do-something old-end))
>>> >>
>>> >> Still not there - I can't assume that "newtext" will have the same
>>> >> length as the thing it replaced...
>>> >
>>> > Sorry, I misread what you wanted. 
>>> >
>>> >     (let ((new-end (+ (prog1 (match-beginning 1)
>>> >                          (replace-match new-text t t string 1)))
>>> >                       (length new-text)))
>>> >        (do-somthing-from new-end))
>>> 
>>> Thanks!  That's easy, and indeed it will work, since the length of the
>>> replacement is fixed in my use-case.
>>
>> Yeah, this would be trickier if new-text contained back-references.
>
> Not very much:
>
>     (let ((end        (match-end 1))
>           (new-string (replace-match new-text t t string 1)))
>       (do-something-from new-string
>                          (+ end (- (length string) (legnth new-string)))))

I give up.  It seems that a PhD in math is not enough to deal with
string-length arithmetic;-).  Shame on me!  (OTOH, mails from you often
teach me that when I have the impression that I'm smart, it's usually
only an impression.)

Thanks a lot!

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University