(* 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.

(* A linear combination is a multiple product *)
Lemma cbl_mprod vs v : cbl vs v ->
exists ks, length ks = length vs /\ v = ks *X* vs.