fact: Definition cpbranch (et : colseq) : ctree := if et is [:: _, e & et'] then if e == Color0 then CtreeEmpty else cfcbr1 (edge_rot e) et' else CtreeEmpty.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color coloring cfmap ctree)