(* This file is distributed under the terms of the MIT License, also known as the X11 Licence.  A copy of this license is in the README file that accompanied the original distribution of this file.  Based on code written by: Brian Aydemir *)
(** Assorted facts about lists. *)
Open Scope list_scope.
(* ********************************************************************** *)
(** * List structure *)
(* ********************************************************************** *)
(** * List membership *)
(* ********************************************************************** *)
(** * List non-membership *)

Lemma not_In_cons : forall (A : Type) (ys : list A) (x y : A),
x <> y ->
~ In x ys ->
~ In x (y :: ys).