proposition: Lemma subr_lteif0r C x y : (0 < y - x ?<= if C) = (x < y ?<= if C).
proof: Proof. by case: C => /=; rewrite subr_gte0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)