Lisp newbie needs help

From: Valentin Hans (ValHa_at_web.de)
Date: 09/30/04 

Date: 30 Sep 2004 07:26:30 -0700

Hello,
regarding Lisp programming I am an absolute newbie. I just started
learning Common Lisp a few days ago and I have got a problem. I wanted
to write a small game and my code contains the following function that
throws a dice until the thrown number is a "1". However, CLISP (I am
using version 2.33) never prints "One thrown". Could anyone please
figure out why this is so?

(defun my-test (&aux (sum 0))
        (do () (nil nil)
                (let ((number (+ (random 6) 1)))
                        (if (= number 1)
                                (format t "~&One thrown." (setf sum 0) (return)))
                        (format t "~&~D thrown. Sum: ~D" number (incf sum number)))))

(I know that "sum" is quite useless here; the function above is just a
stripped down version of the function I am using)