Corollary Zlength_upto : forall n, Zlength (upto n) = Z.of_nat n.

Lemma In_upd_Znth_old : forall {A}{d: Inhabitant A} i (x y : A) l, In x l -> x <> Znth i l -> 0 <= i <= Zlength l -> In x (upd_Znth i l y).