End Permutation.
#[global]
Hint Resolve Permutation_refl perm_nil perm_skip : core.
(* These hints do not reduce the size of the problem to solve and they must be used with care to avoid combinatoric explosions *)
Local Hint Resolve perm_swap perm_trans : core.
Local Hint Resolve Permutation_sym Permutation_trans : core.
(* This provides reflexivity, symmetry and transitivity and rewriting on morphims to come *)
#[global]
Instance Permutation_Equivalence A : Equivalence (@Permutation A) := {
Equivalence_Reflexive := @Permutation_refl A ;
Equivalence_Symmetric := @Permutation_sym A ;
Equivalence_Transitive := @Permutation_trans A }.

(* Specifications: *)
Lemma Permutation_morph_transp A : forall P : list A -> Prop,
(forall a b l1 l2, P (l1 ++ a :: b :: l2) -> P (l1 ++ b :: a :: l2)) ->
Proper (@Permutation A ==> Basics.impl) P.