Section Properties.
Implicit Types x y : TVar.
Implicit Types xs ys : list TVar.
(* ---------------------------------------------------------------------- *)
(** **** Abstract properties of ok *)
(* ---------------------------------------------------------------------- *)
(** **** Properties of binds *)

(** Binds and ok. *)
Theorem binds_concat_ok_comm : forall A x (v : A) (F G : gen_env A),
binds x v (F & G) ->
ok (F & G) ->
binds x v (G & F).