proposition: Lemma gtrBl x y : (x - y < x) = (0 < y).
proof: Proof. by rewrite ltrBlDl ltrDr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)