proposition: Lemma gerDr x y : (y + x <= x) = (y <= 0).
proof: Proof. by rewrite -{2}[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)