proposition: Lemma diff_gt0 (x y : creal) (lt_xy : (x < y)%CR) : diff lt_xy > 0.
proof: Proof. by rewrite /diff; case: (sigW _)=> /= d /andP[]. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(bigop order ssralg ssrnum ssrint rat poly polydiv polyorder) mathcomp(perm matrix mxpoly polyXY binomial bigenough)