proposition: Lemma lteifNr0 C x : - x < 0 ?<= if C = (0 < x ?<= if C).
proof: Proof. by case: C; rewrite /= (oppr_le0, oppr_lt0). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)