(*s Adding a lis of adresses connected to [root] with weight $0$ *)

Fixpoint CG_add_root (root : ad) (cg : CGraph1) (l : list ad) {struct l} :
 CGraph1 :=
  match l with
  | nil => cg
  | x :: l' => CG_add_root root (CG_add cg root x Dz) l'
  end.

Lemma CG_add_root_rooted_4 : forall (l : list ad) (cg : CGraph1) (root a : ad), in_dom _ a (CG_add_root root cg l) = true -> {a = root} + {in_dom _ a cg = true}.