proposition: Lemma expand_eqNoo r : (expand r == -oo) = (r <= -1)%R.
proof: Proof. rewrite /expand; case: ifP => /= r1; last by case: ifP. by apply/esym/negbTE; rewrite -ltNge (lt_le_trans _ r1) // -subr_gt0 opprK. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap) mathcomp(mathcomp_extra) signed