proposition: Lemma anti_mono : {mono f : x y / aR x y >-> rR x y} -> {mono f : x y / aR' x y >-> rR' x y}.
proof: Proof. by move=> mf x y; rewrite rR'E aR'E mf inj_eq //; apply: mono_inj. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool)