proposition: Lemma lerNr x y : (x <= - y) = (y <= - x).
proof: Proof. by rewrite (monoRL opprK lerN2). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)