(* * Tapes-Lift *)
(* Select the [m] elements of [V], of that their index is in [I] *)
Definition select (m n: nat) (X: Type) (I : Vector.t (Fin.t n) m) (V : Vector.t X n) : Vector.t X m :=
Vector.map (Vector.nth V) I.

Lemma lookup_index_vector_None (m n : nat) (I : Vector.t (Fin.t n) m) (i : Fin.t n) :
(~ Vector.In i I) ->
lookup_index_vector I i = None.