(* This file are developed by Qinxiang Cao, Shengyi Wang and Aquinas Hobor in 2015 *)
(* summer in Yale-NUS.                                                             *)
Require Export Coq.Classes.Morphisms.

Lemma In_Permutation_cons: forall {A : Type} (l : list A) (x : A),
In x l ->
exists l', Permutation l (x :: l').