proposition: Lemma lerB_real x y : x <= y -> y - x \is real.
proof: Proof. by move=> le_xy; rewrite ger0_real // subr_ge0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)