(* Quite useful, taken from CDuce, cduce/misc/custom.ml *)
module type Set = sig
  include Set.S
  val hash : t -> int
  val equal : t -> t -> bool
end

module type T = sig
  type t
    (* Debugging *)
  val dump : Format.formatter -> t -> unit
  val check : t -> unit (* Check internal invariants *)

  (* Data structures *)
  val equal : t -> t -> bool
  val hash : t -> int
  val compare :t -> t -> int
  val print : Format.formatter -> t -> unit
end

module type TAG =
sig
  include T
  val attribute : t
  val pcdata : t
  val to_string : t -> string
  val tag : string -> t
end

module type BINARY_TREE =
  functor (Tag:TAG) ->
sig
  include T
  module Tag : TAG with type t = Tag.t
  val parse_xml_uri : string -> t
  val parse_xml_string : string -> t

  val root : t -> t

  val is_string : t -> bool
  val is_node : t -> bool
  val is_nil : t -> bool

  val string : t -> string
  val first_child : t -> t
  val next_sibling : t -> t
  val parent : t -> t

  val id : t -> int
  val tag : t -> Tag.t

  val print_xml : out_channel -> t -> unit
  val size : t -> int*int*int*int
end
module type BINARY_TREE_S =
sig
  include T
  module Tag : TAG
  val parse_xml_uri : string -> t
  val parse_xml_string : string -> t

  val root : t -> t

  val is_string : t -> bool
  val is_node : t -> bool
  val is_nil : t -> bool

  val string : t -> string
  val first_child : t -> t
  val next_sibling : t -> t
  val parent : t -> t

  val id : t -> int
  val tag : t -> Tag.t

  val print_xml : out_channel -> t -> unit
  val dump : Format.formatter -> t -> unit
  val size : t -> int*int*int*int
end