Re: emacs lisp programming help

Re: emacs lisp programming help

[Pascal J. Bourguignon]

ramestica@gmail.com writes:
> in my .emacs. file I have some logic for setting my prefer font. I

In general, emacs questions (even emacs lisp) would be better answered
in one of the emacs newsgroups, such as news:gnu.emacs.help.  However,
this one is not specific to emacs, so we'll answer here:


> tried something like this:
>
> ;; f-name and f-size-default are strings set to something
> ;; reasonable
> (setq my-default-font (concat f-name f-size-default))
> (add-to-list 'default-frame-alist '(font . my-default-font))
>
> then when I start emacs I get logs like this
>
> frame-notice-user-settings: Invalid font: my-default-font
>
> It seems to be a lisp thing that I cannot grasp. Why is that the value
> of my-default-font is not replaced in the last expression?

What does the quote do?  What does 'x evaluate to?
And what does '(a b c) evaluate to?
And what does '(a . b) evaluate to?
So what does '(font . my-default-font) evaluate to?
What other mean to create a cons cell do you know?

-- 
__Pascal Bourguignon__

Re: emacs lisp programming help

[ramestica]

On Jan 29, 1:13 pm, p...@informatimago.com (Pascal J. Bourguignon)
wrote:
> In general, emacs questions (even emacs lisp) would be

I was about to do that but then I hesitated and look for a forum with
the word 'lisp' on it.

> What does the quote do?  What does 'x evaluate to?
> And what does '(a b c) evaluate to?
> And what does '(a . b) evaluate to?
> So what does '(font . my-default-font) evaluate to?

I cannot really answer these questions. I do not know.

> What other mean to create a cons cell do you know?

Using (cons ...), that helped. Many many thanks for the help.

Rodrigo

Re: emacs lisp programming help

[Pascal J. Bourguignon]

ramestica@gmail.com writes:

> On Jan 29, 1:13 pm, p...@informatimago.com (Pascal J. Bourguignon)
> wrote:
>> In general, emacs questions (even emacs lisp) would be
>
> I was about to do that but then I hesitated and look for a forum with
> the word 'lisp' on it.
>
>> What does the quote do?  What does 'x evaluate to?
>> And what does '(a b c) evaluate to?
>> And what does '(a . b) evaluate to?
>> So what does '(font . my-default-font) evaluate to?
>
> I cannot really answer these questions. I do not know.

You can either know it by learning more emacs lisp, 
http://www.gnu.org/software/emacs/manual/elisp.html
http://www.delorie.com/gnu/docs/emacs-lisp-intro/emacs-lisp-intro_toc.html

or by asking emacs itself to give you the answer.

Go in the *scratch* buffer, put it in emacs-lisp-mode
(type M-x emacs-lisp-mode RET)
then type: 

'x C-u C-x C-e
'(a b c) C-u C-x C-e
'(a . b) C-u C-x C-e
'(font . my-default-font) C-u C-x C-e

and compare with:
(setq x 42) C-x C-e
x C-u C-x C-e
(a b c) C-u C-x C-e   (type q to get out of the debugger)
(list 'a 'b 'c)  C-u C-x C-e
(a . b) 
(cons 'a 'b)


With C-x C-e, the previous s-exp is evaluated and the result is printed in the mini buffer.
With C-u C-x C-e, the result is inserted at the point in the current buffer.

An alternative is to call up the REPL: M-x ielm RET
and then you can type your emacs lisp expressions and just type RET to get the result:

'x RET
'(a b c) RET
(list 'a 'b 'c) RET
etc...


Notice that you can use C-x C-u in almost all the modes, so if you
need to insert repeatitive code, you can quickly do it by writting  a
lisp expression to do so;

(dolist (color '(red green blue))
  (insert (format "this->setPlane(Color::%s,other->getPlane(Color::%s));\n" color color)))
C-x C-e 
inserts:
this->setPlane(Color::red,other->getPlane(Color::red));
this->setPlane(Color::green,other->getPlane(Color::green));
this->setPlane(Color::blue,other->getPlane(Color::blue));

(and you can keep the emacs lisp code in a C comment if you may need
to change it later).

>> What other mean to create a cons cell do you know?
>
> Using (cons ...), that helped. Many many thanks for the help.
>
> Rodrigo

-- 
__Pascal Bourguignon__

Emacs lisp programming help

[yeogirl]

Can anyone write me a short emacs list programming which changes its
buffer to corresponding .h or .cc files?

For example, if I work on a buffer, foo.cc and I want to switch to
buffer foo.h, I like to use a hot key such as meta-h to change to
foo.h. I can also do the same hot key change back to foo.cc. I used to
have the feature in my old machine...but I misplaced the code!

Anyhelp would be greatly appreciated!! Thank you!!

Yeogirl.

PS. PLEASE email me your message when you post a reply!! THANKS!!

Re: Emacs lisp programming help

[Pascal Bourguignon]

yeogirl@gmail.com writes:

> Can anyone write me a short emacs list programming which changes its
> buffer to corresponding .h or .cc files?
>
> For example, if I work on a buffer, foo.cc and I want to switch to
> buffer foo.h, I like to use a hot key such as meta-h to change to
> foo.h. I can also do the same hot key change back to foo.cc. I used to
> have the feature in my old machine...but I misplaced the code!
>
> Anyhelp would be greatly appreciated!! Thank you!!

(require 'cl)

(defvar *c-sources-extensions* '("cc" "c" "m" "c++" "C"))

(defun* swap-h-c ()
  (interactive)
  (let* ((name (buffer-file-name))
         (exte (file-name-extension name)))
     (cond ((string= "h" exte)
            (dolist (ext *c-sources-extensions*)
               (let ((other (format "%s.%s" 
                                (file-name-sans-extension name) ext)))
                (when (file-exists-p other)
                    (find-file other)
                    (return-from swap-h-c))))
             (find-file  (format "%s.%s" 
                                (file-name-sans-extension name) 
                                (first  *c-sources-extensions*))))
           ((member* exte *c-sources-extensions* :test (function string=))
             (find-file (format "%s.%s" 
                                (file-name-sans-extension name) "h")))
           (t (beep)))))

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

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