proposition: Lemma ltrNl x y : (- x < y) = (- y < x).
proof: Proof. by rewrite (monoLR 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)