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