Operate on region string

Operate on region string

[Hadron Quark]

Whats the "de-facto" recommended way to work on a region?

I guess the sequence is something like

        (setq t (region-text))
        (setq t (dowork-on-text((t))))
        (replace-region(t))

What is the correct approach?

-- 

Re: Operate on region string

[Tassilo Horn]

Hadron Quark <hadronquark@gmail.com> writes:

Hi Hadron,

> Whats the "de-facto" recommended way to work on a region?
>
> I guess the sequence is something like
>
>         (setq t (region-text))
>         (setq t (dowork-on-text((t))))
>         (replace-region(t))
>
> What is the correct approach?

Here's a samplte function which operates on a region. It reverses the
lines of the region, boxquotes it and titles the boxquote (needs
boxquote.el):

                  +-------------------------------+
                  |The beginning and end positions|
                  |of the marked region.          |
                  +-------------------------------+
                                   X
                                  / \
                                 /   \
(defun reverse-boxquote-region (BEG END)
  (interactive "r") ;; <-- "r" means: "Operate on a region"
                    ;; see C-h f interactive RET
  (reverse-region BEG END)
  (boxquote-region BEG END)
  (boxquote-title "Reversed and boxquoted region"))

Bye,
Tassilo
-- 
   "Mein Baby bekommt nur Trockenmilch, da brauche ich hinterher nur
                             abzustauben."

Re: Operate on region string

[Pascal Bourguignon]

Hadron Quark <hadronquark@gmail.com> writes:

> Whats the "de-facto" recommended way to work on a region?
>
> I guess the sequence is something like
>
>         (setq t (region-text))
>         (setq t (dowork-on-text((t))))
>         (replace-region(t))
>
> What is the correct approach?

1- DO NOT ASSIGN to CONSTANTS!

2- Know your constants: NIL, T, the keywords [starting with ':'], 
   and anything else declared with defconst.

3- Know your programming language and your library functions.  There
   is no function named t [so you cannot call it with (t)], and in
   emacs lisp, which is a lisp-2, contrarily to scheme which is a
   lisp-1, it's meaning less for the operator in a form to be anything
   else than a symbol or a lambda expression [therefore, no ((f))].

4- There is no region-text function in emacs.  You can use
   buffer-substring or buffer-substring-no-properties.

5- There is no function replace-region in emacs.  You can use
   delete-region and insert.

But if you want the best performances, emacs is optimized to work in
the buffers, not on strings.  So if you can do it, better to directly
modify the buffer:

(defun my-command (start end)
  (interactive "r")
  (do-work-on-region start end))


-- 
__Pascal Bourguignon__                     http://www.informatimago.com/

"Indentation! -- I will show you how to indent when I indent your skull!"

Re: Operate on region string

[Hadron Quark]

Pascal Bourguignon <pjb@informatimago.com> writes:

> Hadron Quark <hadronquark@gmail.com> writes:
>
>> Whats the "de-facto" recommended way to work on a region?
>>
>> I guess the sequence is something like
>>
>>         (setq t (region-text))
>>         (setq t (dowork-on-text((t))))
>>         (replace-region(t))
>>
>> What is the correct approach?
>
> 1- DO NOT ASSIGN to CONSTANTS!

I should have but "text"...

>
> 2- Know your constants: NIL, T, the keywords [starting with ':'], 
>    and anything else declared with defconst.

it was just pseudo code : but I take your point.

>
> 3- Know your programming language and your library functions.  There
>    is no function named t [so you cannot call it with (t)], and in

typo : see above.

>    emacs lisp, which is a lisp-2, contrarily to scheme which is a
>    lisp-1, it's meaning less for the operator in a form to be anything
>    else than a symbol or a lambda expression [therefore, no ((f))].
>
> 4- There is no region-text function in emacs.  You can use
>    buffer-substring or buffer-substring-no-properties.

It really wasnt code : see above ... :-;

>
> 5- There is no function replace-region in emacs.  You can use
>    delete-region and insert.
>
> But if you want the best performances, emacs is optimized to work in
> the buffers, not on strings.  So if you can do it, better to directly
> modify the buffer:
>
> (defun my-command (start end)
>   (interactive "r")
>   (do-work-on-region start end))

this is what I wanted to know : what is the best way to "do-work-on-region"?



-- 

Re: Operate on region string

[Hadron Quark]

Tassilo Horn <heimdall@uni-koblenz.de> writes:

> Hadron Quark <hadronquark@gmail.com> writes:
>
> Hi Hadron,
>
>> Whats the "de-facto" recommended way to work on a region?
>>
>> I guess the sequence is something like
>>
>>         (setq t (region-text))
>>         (setq t (dowork-on-text((t))))
>>         (replace-region(t))
>>
>> What is the correct approach?
>
> Here's a samplte function which operates on a region. It reverses the
> lines of the region, boxquotes it and titles the boxquote (needs
> boxquote.el):
>
>                   +-------------------------------+
>                   |The beginning and end positions|
>                   |of the marked region.          |
>                   +-------------------------------+
>                                    X
>                                   / \
>                                  /   \
> (defun reverse-boxquote-region (BEG END)
>   (interactive "r") ;; <-- "r" means: "Operate on a region"
>                     ;; see C-h f interactive RET
>   (reverse-region BEG END)
>   (boxquote-region BEG END)
>   (boxquote-title "Reversed and boxquoted region"))

Thanks Tassilo - but this isnt showing me how to actually do anything
myself with the text string contained by the region if you get my
meaning.

I tried reading the code in boxquote, but there are too many function
calls not documented. 

Maybe you could help?

I want something like this to work on a buffer region

(defun remove-vowels-region(te)
  "Remove the vowels"
  (interactive "sTe:")
  (replace-regexp-in-string "[aeiouAEIOU]" "" te)
)

I hilite some text and then call remove-vowels-in-region.

A first step would be sufficient to get me on my way : I'm not a lisp
programmer but am learning a little.

>
> Bye,
> Tassilo

-- 

Re: Operate on region string

[Tassilo Horn]

Hadron Quark <hadronquark@gmail.com> writes:

Hi Hadron,

> I want something like this to work on a buffer region
>
> (defun remove-vowels-region(te)
>   "Remove the vowels"
>   (interactive "sTe:")
>   (replace-regexp-in-string "[aeiouAEIOU]" "" te)
> )

Try that:

(defun remove-vowels-region (start end)
  (interactive "r")
  (replace-regexp "[aeiouAEIOU]" "" nil start end))

Bye,
Tassilo
-- 
[Emacs] is written in Lisp, which is the only computer language that is
beautiful.  -- Neal Stephenson, _In the Beginning was the Command Line_

Re: Operate on region string

[Mathias Dahl]

Hadron Quark <hadronquark@gmail.com> writes:

> I want something like this to work on a buffer region
>
> (defun remove-vowels-region(te)
>   "Remove the vowels"
>   (interactive "sTe:")
>   (replace-regexp-in-string "[aeiouAEIOU]" "" te)
> )
>
> I hilite some text and then call remove-vowels-in-region.

What about this:

(defun remove-vowels-in-region (beg end)
  (interactive "r")
  (save-excursion
    (goto-char beg)
    (while (search-forward-regexp "[aeiouAEIOU]" end nil)
      (replace-match ""))))

/Mathias

Re: Operate on region string

[Hadron Quark]

Mathias Dahl <brakjoller@gmail.com> writes:

> Hdrn Qrk <hdrnqrk@gml.cm> wrts:
>
>>  wnt smthng lk ths t wrk n  bffr rgn
>>
>> (dfn rmv-vwls-rgn(t)
>>   "Rmv th vwls"
>>   (ntrctv "sT:")
>>   (rplc-rgxp-n-strng "[]" "" t)
>> )
>>
>>  hlt sm txt nd thn cll rmv-vwls-n-rgn.
>
> Wht bt ths:
>
> (dfn rmv-vwls-n-rgn (bg nd)
>   (ntrctv "r")
>   (sv-xcrsn
>     (gt-chr bg)
>     (whl (srch-frwrd-rgxp "[]" nd nl)
>       (rplc-mtch ""))))
>
> /Mths

Wrks grt thnks : 'll stp thrgh nd lrn frm t - thnks  lt.

:)


-- 

Re: Operate on region string

[Hadron Quark]

Tassilo Horn <heimdall@uni-koblenz.de> writes:

> Hadron Quark <hadronquark@gmail.com> writes:
>
> Hi Hadron,
>
>> I want something like this to work on a buffer region
>>
>> (defun remove-vowels-region(te)
>>   "Remove the vowels"
>>   (interactive "sTe:")
>>   (replace-regexp-in-string "[aeiouAEIOU]" "" te)
>> )
>
> Try that:
>
> (defun remove-vowels-region (start end)
>   (interactive "r")
>   (replace-regexp "[aeiouAEIOU]" "" nil start end))
>
> Bye,
> Tassilo

vn shrtr nd swtr!

(even shorter and sweeter)

thanks!

-- 

Re: Operate on region string

[Pascal Bourguignon]

Hadron Quark <hadronquark@gmail.com> writes:
>> But if you want the best performances, emacs is optimized to work in
>> the buffers, not on strings.  So if you can do it, better to directly
>> modify the buffer:
>>
>> (defun my-command (start end)
>>   (interactive "r")
>>   (do-work-on-region start end))
>
> this is what I wanted to know : what is the best way to "do-work-on-region"?

You need to learn the emacs lisp functions, notably those who work on
the buffers and on the strings.

Most of the functions that work on the buffers are actually commands
that are also bound to some keys and that you use.

For example, if you want to remove every other character in the region, 
you can do it manually with C-f C-d C-f C-d ...

You can know what functions are called when you type C-f or C-d:

    C-h k C-f
    C-h k C-d

You need to know also the current position of the cursor.  It's given
by the function point.

Then you can write a loop:

(defun delete-every-other-character (start end)
   (interactive "r")
   (goto-char start)
   (while (< (point) end)
      (forward-char 1)
      (delete-char 1)
      (setf end (1- end))))

The best, to know all these functions is to read the emacs lisp manual.


Execute these forms:

   (info "Emacs-lisp-intro") 
   (info "Elisp")

Type:

   (info "Elisp") C-x C-e 

in the buffer *scratch*

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/

READ THIS BEFORE OPENING PACKAGE: According to certain suggested
versions of the Grand Unified Theory, the primary particles
constituting this product may decay to nothingness within the next
four hundred million years.

Re: Operate on region string

[John Sullivan]

Hadron Quark <hadronquark@gmail.com> writes:

> Wrks grt thnks : 'll stp thrgh nd lrn frm t - thnks  lt.

Depending on how many or what kind of operations you want to do on a region,
you may find it helpful to narrow to the region in the buffer that you are
operating on.

See narrow-to-region.

-- 
-John Sullivan
-http://www.wjsullivan.net
-GPG Key: AE8600B6

Re: Operate on region string

[robert.thorpe]

Hadron Quark wrote:
> Tassilo Horn <heimdall@uni-koblenz.de> writes:
>
> > Hadron Quark <hadronquark@gmail.com> writes:
> >
> > Hi Hadron,
> >
> >> I want something like this to work on a buffer region
> >>
> >> (defun remove-vowels-region(te)
> >>   "Remove the vowels"
> >>   (interactive "sTe:")
> >>   (replace-regexp-in-string "[aeiouAEIOU]" "" te)
> >> )
> >
> > Try that:
> >
> > (defun remove-vowels-region (start end)
> >   (interactive "r")
> >   (replace-regexp "[aeiouAEIOU]" "" nil start end))
> >
> > Bye,
> > Tassilo
>
> vn shrtr nd swtr!
>
> (even shorter and sweeter)

As a sidenote, you look at the problem like this:

* Is there a function that works on a region I can use for my purpose.
If so it is simple like the above.

* If not, maybe there is a function that works on the whole region.  In
this case I can use M-x widen and M-x narrow-to-region to perform an
action on a region.

* If that doesn't work (which is very unlikely) then convert the region
to a string and operate on the string.

Re: Operate on region string

[David Combs]

In article <87lkogz0kj.fsf@thalassa.informatimago.com>,
Pascal Bourguignon  <pjb@informatimago.com> wrote:
>Hadron Quark <hadronquark@gmail.com> writes:
>>> But if you want the best performances, emacs is optimized to work in
>>> the buffers, not on strings.  So if you can do it, better to directly
>>> modify the buffer:
>>>
>>> (defun my-command (start end)
>>>   (interactive "r")
>>>   (do-work-on-region start end))
>>
>> this is what I wanted to know : what is the best way to "do-work-on-region"?
>
>You need to learn the emacs lisp functions, notably those who work on
>the buffers and on the strings.
>
>Most of the functions that work on the buffers are actually commands
>that are also bound to some keys and that you use.
>
>For example, if you want to remove every other character in the region, 
>you can do it manually with C-f C-d C-f C-d ...
>
>You can know what functions are called when you type C-f or C-d:
>
>    C-h k C-f
>    C-h k C-d
>
Easy way to do that:  define the seq as a macro,
  then do "insert-macro" (or whatever it's called) --
  that code shows the function-NAMES too.


David