proposition: Lemma lerDr x y : (x <= y + x) = (0 <= y).
proof: Proof. by rewrite -{1}[x]add0r lterD2. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)