proposition: Lemma ribbonE inn0 inn out0 out : inn0 < out0 -> ribbon (inn0 :: inn) (out0 :: out) = ribbon_from (inn0 :: inn) (out0 :: out).
proof: Proof. by rewrite /= => H; rewrite H /= (gtn_eqF H) /= orbF. Qed.
imports: HB(structures) mathcomp(all_ssreflect) tools sorted partition