Newbie questions



I am trying to find out whether I can use Maxima for teaching. So I installed 
Maxima (and GCL, by the way).

I have written a lisp function $f in a file that is called "mytest.lisp" and 
is in the current directory. It is extremely simple:

(defun $f (x) (* x x))

Can I load this function into maxima and call it? It should return (when 
called from Maxima):

(1) 4 when called like (f 2)
(2) 3+2sqrt(2) when called like (f (+ 1 (sqrt 2)))
(3) a^2+2a+1 when called like (f (+ a 1))

(In the third case, maybe some other function like expand in Maple could be 
nexessary, but this would be o.k. What I mean is, my function should be able 
to handle whatever unput is sensible in Maxima.)

TIA,

Janos Blazi