proposition: Lemma in_skewE inn out b : in_skew inn out b = ~~ in_shape inn b && in_shape out b.
proof: Proof. by rewrite /in_skew /in_shape -leqNgt andbC. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(div ssralg ssrint ssrnum binomial) tools combclass sorted ordtype