#[export]
Instance Permutation_cons A :
Proper (Logic.eq ==> @Permutation A ==> @Permutation A) (@cons A).
Section Permutation_properties.
Variable A B:Type.
Implicit Types a : A.
Implicit Types l m : list A.
(** Compatibility with others operations on lists *)

(* Specifications: *)
Theorem Permutation_in : forall (l l' : list A) (x : A),
Permutation l l' -> In x l -> In x l'.