Hint Resolve Equal_hom_refl.
Hint Resolve Equal_hom_sym.
(* "set" of all morphisms of a category *)
Section arrs_setoid_def.
Variable C : Category.
Structure Arrs : Type :=  {Dom : C; Codom : C; Arrow : Dom --> Codom}.
Definition Equal_Arrs (f g : Arrs) := Arrow f =_H Arrow g.

(* Specifications: *)
Lemma Equal_Arrs_equiv : Equivalence Equal_Arrs.
End arrs_setoid_def.