(************************************************************
   touple_set.ml	Created      : Sun Nov  3 02:04:04 2002
  			Last modified: Sun Nov 03 02:10:03 2002
  Compile: ocamlopt.opt touple_set.ml -o touple_set #
************************************************************)
(**

  @author Takashi Masuyama <mamewo@dk9.so-net.ne.jp>

*)

module StringTouple =
  struct
    type t = string * string
    let compare (x1,y1) (x2,y2) =
      if x1 < x2 then -1
      else if x1 = x2 then 
	if y1 < y2 then -1
	else if y1 = y2 then 0
	else 1
      else 1
  end

module StringToupleSet = Set.Make(StringTouple)

let _ =
  let data = [("hoge","moge"); ("tak", "mamewo"); ("aki", "okui") ] in
  StringToupleSet.iter (fun (x,y) -> Printf.printf "%s\t%s\n" x y)
    (List.fold_right StringToupleSet.add data StringToupleSet.empty)