Re: deffoo?

[Emanuel Berg <embe8573@student.uu.se>]

Nikolaus Rath <Nikolaus@rath.org> writes:

> One thing I stumbled upon is the use of "deffoo" and
> "defvoo". The help did not help me at all ("The same
> as `defun', only register FUNC").
>
> Can someone explain what this macros do / how they
> differ from defun / defvar?

Use the source, Luke!

    (defmacro deffoo (func args &rest forms)
      "The same as `defun', only register FUNC."
      `(prog1
           (defun ,func ,args ,@forms)
         (nnoo-register-function ',func)))

So the difference is nothing more than

    (nnoo-register-function ',func)

 - you could equally well do

    (defun make-soap () ...)
    (nnoo-register-function 'make-soap)

`nnoo-register-function' isn't documented, but it
is defined like this:

    (defun nnoo-register-function (func)
      (let ((funcs (nthcdr 3 (assoc (nnoo-backend func)
                nnoo-definition-alist))))
        (unless funcs
          (error "%s belongs to a backend that hasn't been declared" func))
        (setcar funcs (cons func (car funcs)))))

You can grep the Emacs and/or Gnus source to find out
when those vars are used (or search the Gnus manual) -
however, often this would be a backward way to
do things.

Rather, you will find `nnoo-register-function' when
you need it, and then you will understand exactly what
it does, is the way it works most of the time.

Good luck!

-- 
underground experts united
http://user.it.uu.se/~embe8573