fact: Definition add_edge_face (z : ecp_dart G) : ecp_dart G := match z with | IcpX => Icp y | IcpXe => Icp x | Icp z' => if face z' == x then IcpX else if face z' == y then IcpXe else Icp (face z') end.
imports: mathcomp(all_ssreflect) GraphTheory(edone preliminaries bij) fourcolor(hypermap geometry cfmap jordan color coloring combinatorial4ct) fourcolor(walkup)