fact: Fixpoint ctrmask_rec (cci : seq nat) i n {struct n} : bitseq := if n is n'.+1 then (i \in cci) :: ctrmask_rec cci i.+1 n' else [::].
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap geometry color coloring cfmap ctree) fourcolor(cfcolor)