proposition: Lemma ltrNr x y : (x < - y) = (y < - x).
proof: Proof. by rewrite (monoRL opprK (leW_nmono _)). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)