module type OrderedType = Set.OrderedType

module type S = sig
  type label
  type ('v, 'e) t

  type 'v vertex := label * 'v
  type 'e edge := label * label * 'e

  val make: 'v vertex list -> 'e edge list -> ('v, 'e) t
  val make': label list -> 'e edge list -> (label, 'e) t
  val make_e: 'e edge list -> (label, 'e) t

  val count_vertices: ('v, 'e) t -> int
  val count_edges:    ('v, 'e) t -> int

  val rev: ('v, 'e) t -> ('v, 'e) t

  val iter_dfs: ('v -> 'v -> 'e -> unit) -> ('v, 'e) t -> label -> unit
end