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