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Re: Newbie regexp question


From: Friedrich Dominicus
Subject: Re: Newbie regexp question
Date: 31 Oct 2002 15:41:22 +0100
User-agent: Gnus/5.0808 (Gnus v5.8.8) XEmacs/21.4 (Common Lisp)

Paul Cohen <address@hidden> writes:

> Hi all,
> 
> Thanks to everyone who has been kind to take time to answer my question! 
> Jay's answer is definitely closest to solving my problem.
> 
> "Bingham, Jay" wrote:
> 
> > After seeing Mike and Friedrich's exchange on your question I decided to 
> > create my own solution, a general purpose function that allows the user to 
> > specify the start and end as regular expressions and supply a replacement 
> > for the text between them, and optionally by giving a numeric prefix 
> > argument to the function force it to replace the tags as well.
> 
> Neat.
> 
> > In the process I noticed that Mike's function has a logic flaw.  It will 
> > never find the case of a missing end tag and instead deletes that final 
> > start tag.
> 
> Ok.
> 
> > Here is my function if you want it.
> 
> Yes I do! :-)
> 
> >
> > (defun replace-between-regexp (start-re end-re repl-str &optional incl)
> >   "Replace the text between two regular expressions supplied as arguments.
> > With a numeric argument the regular expressions are included.
> > When called non interactively incl should be nil for non-inclusion and
> > non-nil for inclusion."
> >   (interactive "sStart regexp: \nsEnd regexp: \nsReplace between %s and %s 
> > with: \nP")
> >   (while (re-search-forward start-re nil t)
> >     (let ((beg (if incl (match-beginning 0) (match-end 0)))
> >           (end
> >            (progn
> >              (if (re-search-forward end-re nil t)
> >                  (if incl (match-end 0) (match-beginning 0))
> >                nil))))
> >       (if (not end)
> >           (error "Unmatched \"%s\" sequence at position %d" start-re beg)
> >         (delete-region beg end)
> >         (insert repl-str)))))
> 
> I have few comments/questions.
> 
> I tried the above function in my *scratch* buffer by writing it and then 
> adding the following lines (with line numbers!):
> 
> 19. (replace-between-regexp "<!--Test-->" "<!--End of Test-->" "" 1)
> 20.
> 21. Pub
> 22. <!--Test-->
> 23. Foo
> 24. <!--End of Test-->
> 25. Bar
> 
> I then evaluated the function with C-j. This resulted in:
> 
> 19. (replace-between-regexp "<!--Test-->" "<!--End of Test-->" "" 1)
> 20.
> 21.
> 22. Pub
> 23. nil
> 24.
> 25. Bar
> 
> With the cursor on line 24. My comments/questions are:
> 
> 1) I understand that the "nil" on line 23 comes from the value of
> the last item in the function list, in this case "(insert
> repl-str)". But there is also a newline character is inserted after
> "nil". But I don't want either the "nil" or the extra newline
> character! 
I'm a bit lazy to answer all or suggest other things but here's are my
thoughts on that
Call it with (replace-betwe.... "<!-- End of Test" nil t)

than check before the output
(when repl-string (insert repl-string))


> 
> 2) Line 21 containing "pub" is moved forward to line 22. I guess
> this is just because I did C-j at the end of line 19 or?
Check the documentation of C-j
C-h k C-j gives it to you
> 
> 3) It would be nice if the cursor would return to its original
> position after running the command. I tried adding the
> "save-excursion" command after the "interactive" line in the function
>but it didn't work. The cursor still ended up on line 24.
You have to enclose it all in save-excursion

It looks like this than:
(defun replace-between-regexp (start-re end-re repl-str &optional incl)
  "Replace the text between two regular expressions supplied as arguments.
 With a numeric argument the regular expressions are included.
 When called non interactively incl should be nil for non-inclusion and
 non-nil for inclusion."
  (interactive "sStart regexp: \nsEnd regexp: \nsReplace between %s
and %s with: \nP")
  (save-excursion
    (while (re-search-forward start-re nil t)
      (let ((beg (if incl (match-beginning 0) (match-end 0)))
            (end
             (progn
               (if (re-search-forward end-re nil t)
                   (if incl (match-end 0) (match-beginning 0))
                 nil))))
        (if (not end)
            (error "Unmatched \"%s\" sequence at position %d" start-re beg)
          (delete-region beg end)
          (when repl-str (insert repl-str)))))))

Do not use C-j than but C-x C-e 

This is the documentation for C-j
Documentation:
Evaluate sexp before point; print value into current buffer.
So you will get nil after this run

C-x C-e runs


Documentation:
Evaluate sexp before point; print value in minibuffer.
With argument, print output into current buffer.

So the output will be put into the minibuffer.

> 
> 4) The idea to solve my problem with a lisp function is neat and I
> guess there are many situations where one would like to add ones own
> special purpose functions to Emacs. My question is: where is the
> suitable place to put them? In my .emacs file or in a separate
> file. What are the conventions? 
.emacs is change quite frequently. I don't think you self-written
functions will after development, therfor put them into an own file,
byte-compiler that file and load it from the .emacs file.

I've put all my stuff under .xemacs here and libraries I've installed
over time have found there way under ~/lib/elisp. It makes it quite
easy to update other systems such that XEmacs behaves like I want it
too.

It's IMHO nearly unavaiable that you customize your Emacs over time
and you feel like a fish on land while you are used to some things and
they are not there. 

Regards
Friedrich


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