fact: Definition ecpN_node x := match x with | IcpX => if long_cpring x0 then Icp (node x0) else IcpX G | IcpXe => Icp (face (edge x0)) | Icp y => if y == x0 then IcpXe G else if node (node y) == x0 then IcpX G else Icp (node y) end.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)