fact: Definition ecpU_node x := match x with | IcpX => IcpXe G | IcpXe => Icp (node (node x0)) | Icp y => if y == node 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)