proposition: Lemma oppr_gt0 x : (0 < - x) = (x < 0).
proof: Proof. by rewrite ltrNr oppr0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)