(* Iterated contraction *)
Definition mcontra n (ll: list (kn n)) (x: vect n) :=
fold_left (fun x l => #<l,x>#) ll x.
Notation "#<< l , x >>#" := (mcontra _ l x).

Lemma mcontra_hom n k (x: vect n) l :
hom n k x -> hom n (k - length l) #<<l, x>>#.