fact: Fixpoint Birkhoff_check2 ctu1 gtu1 n ctu2 gtu2 := if n isn't n'.+1 then false else if ctree_pick_rev ctu1 ctu2 isn't e :: et then false else do_Birkhoff_check2 (belast e et) ctu1 gtu1 (Birkhoff_check2 ctu2 gtu2 n') && do_Birkhoff_check2 (rev et) ctu2 gtu2 (Birkhoff_check2 ctu1 gtu1 n').
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph) fourcolor(hypermap jordan geometry color chromogram) fourcolor(coloring patch snip sew revsnip kempe) fourcolor(ctree initctree gtree initgtree ctreerestrict) fourcolor(gtreerestrict cfmap cfcolor kempetree)