origin of stupid zetalisp question

[drstrip@cs.sandia.gov (David R. Strip)]

My problem with "//*" seems to come from a further failure to 
understand mode definitions in zmacs. Working from an example I
produced 

(defmethod (:c-mode-forms c-mode-mixin :default) ()
  nil)

(defmethod (:mode-forms c-mode-mixin) ()
  (append (send self :c-mode-forms)
	  '((set-char-syntax list-open *mode-list-syntax-table* #/[)
	    (set-char-syntax list-open *mode-list-syntax-table* #/{)
	    (set-char-syntax list-close *mode-list-syntax-table* #/])
	    (set-char-syntax list-close *mode-list-syntax-table* #/})	    
	    (set-comtab *mode-comtab* '(#\TAB com-tab-insert))
	    (setq *comment-begin* "//*")
	    (setq *comment-end* "*//")
	    (setq *comment-start* "//*"))))

(after several tries, that is). What still has me baffled is how to 
kill a previous def of these methods. I try m-x undefine function on 
them, but the mode forms seem to live on. Thus when I tried to
redefine the *comment-begin* var, I never was seeing the result.

So, how do I override the previous value of the mode forms?
Thanks
Strip