fact: Definition ecp_edge x := match x with | IcpX => IcpXe G | IcpXe => IcpX G | Icp x' => Icp (edge x') end.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color)