fact: Fixpoint cptriad ccm cp i := if i is i'.+1 then let: Cfmask mrt mkt := cpadj (cfmask1 cp i') cp in let: Cfmask mrc mkc := ccm in let mct := mask mrc mrt ++ mask mkc mkt in if has negb mct && (2 < count id mct) then true else cptriad ccm cp i' else false.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color coloring cfmap ctree) fourcolor(cfcolor)