proposition: Lemma mem_pcatT u : (u \in pcat p q) = (u \in p) || (u \in tail q).
proof: Proof. by rewrite !mem_path !nodesE !inE mem_cat -orbA. Qed.
imports: HB(structures) Coq(Setoid CMorphisms) mathcomp(all_ssreflect) GraphTheory(edone preliminaries bij)