proposition: Lemma real_lteif_distl C x y e : x - y \is real -> (`|x - y| < e ?<= if C) = (y - e < x ?<= if C) && (x < y + e ?<= if C).
proof: Proof. by case: C => /= ?; rewrite real_lter_distl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)