proposition: Lemma lteif0Nr C x : 0 < - x ?<= if C = (x < 0 ?<= if C).
proof: Proof. by case: C; rewrite /= (oppr_ge0, oppr_gt0). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)