From: "Pascal J. Bourguignon" <pjb@informatimago.com>
To: help-gnu-emacs@gnu.org
Subject: Re: A variant of match-end, but after replacement?
Date: Mon, 20 Jul 2015 02:33:13 +0200 [thread overview]
Message-ID: <87zj2r3bxy.fsf@kuiper.lan.informatimago.com> (raw)
In-Reply-To: mailman.7165.1437350800.904.help-gnu-emacs@gnu.org
Marcin Borkowski <mbork@mbork.pl> writes:
>> 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 new-string) (length 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.)
Sorry, I was about to write out the equation, but if it's necessary,
I'll do.
(length new-string)
--------------------------------------------------------
(length prefix) (length new) (length suffix)
---------------- ---------------------- ----------------
pppppppppppppppp nnnnnnnnnnnnnnnnnnnnnn ssssssssssssssss
^
|
new-end
(length old-string)
--------------------------------------------------
(length prefix) (length old) (length suffix)
---------------- ---------------- ----------------
pppppppppppppppp oooooooooooooooo ssssssssssssssss
^
|
(match-end)
So, we have:
(= (length suffix) (- (length new-string) new-end))
(= (length suffix) (- (length old-string) (match-end)))
Or, in math:
s = ns-ne
s = os-me
Therefore:
0 = (ns-ne) - (os-me)
<=> 0 = ns - ne - os + me
<=> ne = me + (ns - os)
<=> (= new-end (+ (match-end) (- (length new-string) (length old-string))))
Hence:
(let ((end (match-end 1))
(new-string (replace-match new-text t t old-string 1)))
(do-something-from new-string
(+ end (- (length new-string) (length old-string)))))
--
__Pascal Bourguignon__ http://www.informatimago.com/
“The factory of the future will have only two employees, a man and a
dog. The man will be there to feed the dog. The dog will be there to
keep the man from touching the equipment.” -- Carl Bass CEO Autodesk
next prev parent reply other threads:[~2015-07-20 0:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.7146.1437306572.904.help-gnu-emacs@gnu.org>
2015-07-19 12:06 ` A variant of match-end, but after replacement? Pascal J. Bourguignon
2015-07-19 12:22 ` Marcin Borkowski
2015-07-19 13:25 ` Marcin Borkowski
2015-07-20 10:46 ` Nicolas Richard
[not found] ` <mailman.7147.1437308571.904.help-gnu-emacs@gnu.org>
2015-07-19 12:30 ` Pascal J. Bourguignon
2015-07-19 13:20 ` Marcin Borkowski
2015-07-19 13:26 ` Dmitry Gutov
2015-07-19 19:57 ` Marcin Borkowski
[not found] ` <mailman.7150.1437312076.904.help-gnu-emacs@gnu.org>
2015-07-19 13:41 ` Pascal J. Bourguignon
2015-07-19 19:58 ` Marcin Borkowski
[not found] ` <mailman.7160.1437335923.904.help-gnu-emacs@gnu.org>
2015-07-19 20:18 ` Barry Margolin
2015-07-19 22:45 ` Pascal J. Bourguignon
2015-07-20 0:06 ` Marcin Borkowski
[not found] ` <mailman.7165.1437350800.904.help-gnu-emacs@gnu.org>
2015-07-20 0:33 ` Pascal J. Bourguignon [this message]
2015-07-19 11:49 Marcin Borkowski
2015-07-19 20:23 ` Dmitry Gutov
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