End prodl.
Definition clos_refl {A : Type} (R : A -> A -> Prop) (x y : A) : Prop :=
R x y \/ x = y.

Lemma Forall2_eq_clos_refl (A:Type) (R: A -> A -> Prop) (l1 :list A) :
Forall2 (clos_refl R) l1 l1.