induction i;intros [ | x l ] ;trivial.
simpl;auto.
Qed.

(* Specifications: *)
Lemma Lget_app : forall (A:Set) (a:A) l i,
Lget i (l ++ a :: nil) = if Nat.eqb i (length l) then Some a else Lget i l.
Lemma Lget_app_Some : forall (A:Set) l delta i (a: A),
Lget i l = Some a ->
Lget i (l ++ delta) = Some a.