proposition: Lemma braidrule_homog (u : seq 'I_n) : all [pred v | size v == size u] (braidrule u).
proof: Proof. Proof using. apply/allP => /= v. by rewrite mem_cat => /orP[/braid_abaP | /braidCP] [a] [b] [_ -> ->]. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr