NetNews Usenet Archive 1992 #19/NN_1992_19.iso/spool/gnu/emacs/help/3998

Text File | 1992-09-03 | 1.5 KB | 55 lines

Newsgroups: gnu.emacs.help
Path: sparky!uunet!pipex!demon!edscom!kevin
From: [e-mail] (Kevin Broadey)
Subject: How do I subvert a function?
Message-ID: <[e-mail]>
Sender: [e-mail] (Kevin Broadey)
Organization: EDS-Scicon, Milton Keynes, UK
Distribution: gnu
Date: Fri, 4 Sep 1992 10:01:46 GMT
Lines: 43

I'd like to be able to replace an elisp function with one I've written
myself while keeping hold of the original.

The reason for this is that I want to modify the function's behaviour
slightly without upsetting the other Emacs users on my site and without
the bother of having a private copy of the entire .el file.

I tried doing this:-

;; original.el

...

(defun original ()
  ...)



;; subvert.el

(fset 'old-original 'original)

(defun original ()
  (old-original)
  ;; modify behaviour here
  ...)


The trouble is that (defun original ()...) also affects the function
definition of `old-original', presumably because both symbols are
pointing to the same definition cell, and it is the cell rather than the
pointer that gets hacked by defun.

Needless to say, this makes my function crawl up the stack at an
alarming rate!

So, how do I save a function definition.  Is there a `purecopy' for
functions?
--
Kevin Broadey <[e-mail]>
EDS-Scicon, Wavendon Tower, Wavendon, Milton Keynes, MK17 8LX, England.
Phone: [phone] (direct) or [phone] ext 4198
These opinions are mine: others available on request.