proposition: Lemma oarc_cases e x u y : oarc G e x u y -> is_edge G e x u y \/ is_edge G e y u° x.
proof: Proof. by case => E [[|]] [A B C]; [right|left]. Qed.
imports: HB(structures) Coq(Relation_Definitions Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom rewriting) GraphTheory(finmap_plus)