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Re: Macro used for dynamic setting of font-lock-keywords


From: Sebastian Tennant
Subject: Re: Macro used for dynamic setting of font-lock-keywords
Date: Mon, 28 May 2007 12:22:44 +0300
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/22.0.95 (gnu/linux)

Quoth Xavier Maillard <address@hidden>:
> Hi,
>
>    seem to get used as often as it probably should. I've seen people post 20+
>    lines of elisp to this list to do something which could be achieved more
>    reliably with 4 or five lines of defadvice. 
>
> Advice is considered as *dangerous* and not to be used extensively.
>
Indeed this is what I've been lead to believe.  I think RMS' position
on defadvice, which confirms this, is knocking about somewhere.

IMHO macros (at a user-level) are useful whenever you would otherwise
repeat yourself.  For example, I like to keep technical notes in a
~/tech-notes directory and quotes in a ~/quotes directory.  Rather
than write an interactive command for each I wrote a macro which I
called commandir:

  (defmacro commandir (call pmt dir def)
    `(defun ,call ()
       (interactive)
       (let (checked-dir filename)
       ;; checked-dir will always ends with a '/'
       (setq checked-dir (file-name-as-directory ,dir))
       ;;accept user input
       (setq filename (read-file-name ,pmt checked-dir))
       (when (equal filename "") (setq filename ,def))
       ;;read file or create new buffer if file does not exist
       ;;(buffer is automatically selected for editing)
       (find-file (concat checked-dir filename) nil)
       .
       .
       .

I can now 'build' as many functions as I like, each providing quick
access to the contents of my various directories, with simple macro
calls like this one in my ~/.emacs file:

  (commandir tn "Tech note: " "~/tech-notes" "misc")

Then it is a case of simply typing::

  M-x tn <RET>

and I am prompted for a filename (with filename completion based on
the contents of ~/tech-notes").  If I enter the name of an exisitng
file, that file is visited, if I enter a non-existing file name, that
file will be created when the buffer is saved, and if I don't type
anything, ~/tech-notes/misc is visited.

Very handy indeed!

Sebastian





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