(defun simple (list)
  (cond ((equal 'a (first list))
	 (print "A!")) 
	((equal 'b (first list))
	 (print "B!"))
	(t (error "Can't happen!"))))

(defun check-args (list)
  (dolist (arg list t)
	  (when (not (numberp arg)) (return nil))))

(defun simple2 (list)
  (let ((sum1 0)(sum2 0))
    (when (not (check-args list))
	  (error "simple2: Non-numeric args!"))
    (dolist (element list)
	    (setq sum1 (+ sum1 element)))
    (dolist (element list)
	    (setq sum2 (+ sum2 (* 2 element))))
    (format *standard-output* "First sum: ~a~%Second sum: ~a~%" sum1 sum2)
))