proposition: Lemma vcompE (F G H : functor) (n1 : F ~> H) (n2 : G ~> F) X : (n1 \v n2) X = n1 X \o n2 X.
proof: Proof. by rewrite /= /vcomp /=; unlock. Qed.
imports: ssrmatching mathcomp(all_ssreflect) monae_lib HB(structures) hierarchy