(* Get the constant part of a vector *)
Fixpoint const (n: nat): (vect n) -> K :=
match n return vect n -> K with
| O => fun a => a
| S n1 => fun l => let (l1,l2) := l in const n1 l2
end.
Notation "'C[ x ]" := (const _ x).

Lemma const0 n : 'C[ 0: vect n ] = 0%f.