module type G =sig..end
type t
val n : t -> int
val iter_vertex : (int -> unit) -> t -> unit
val fold_vertex : (int -> 'a -> 'a) -> t -> 'a -> 'a
val iter_succ : (int -> unit) -> t -> int -> unit
val fold_succ : (int -> 'a -> 'a) -> t -> int -> 'a -> 'a
val iter_pred : (int -> unit) -> t -> int -> unit
val fold_pred : (int -> 'a -> 'a) -> t -> int -> 'a -> 'a