(* How to generate the multiple product for a constant *)
Fixpoint lgenk (n: nat) (k: K p) {struct n} : list (K p) :=
match n  with
O => nil
| 1 => k :: nil
| S n1 => k::lgenk n1 k
end.

(* 0 as a multiple product *)
Lemma genk0_mprod vs :  0 = lgenk (length vs) 0%f *X* vs.