(************************************************************
   random.ml		Created      : Wed Jul 31 15:07:54 2002
  			Last modified: Wed Jul 31 16:46:11 2002
  Compile: ocamlc -g random.ml -o random #
  Compile: ocamlopt.opt random.ml -o random #
************************************************************)

let random seed lambda e mu =
  let current = ref seed in
  (* result の初期値は1 *)
  let rec get_p e result =
    if e = 0 then
      result
    else
      get_p (e-1) (2*result) in
  let p = get_p e 1 in
(*  let _ = Printf.printf "p = %d\n" p in*)
  fun () ->
    let result = !current in
    begin
      current := (lambda*result  + mu) mod p;
      result
    end

module ComparebleInt =
  struct
    type t = int
    let compare x y =
      if x < y then -1 else if x = y then 0 else 1
  end

module IntSet = (Set.Make(ComparebleInt) :
		   sig
		     type t
		     val add: int -> t -> t
		     val mem: int -> t -> bool
		     val empty: t
		   end)

let _ =
  let seed = 2 in
  let lambda = 3 in
  let e = 4 in
  let mu = 0 in 
  let r = random seed lambda e mu in
  let s = ref IntSet.empty in
  let i = ref 1 in
  let current = ref (r ()) in
  while not (IntSet.mem !current !s) do
    Printf.printf "%2d: %d\n" !i !current;    
    s := IntSet.add !current !s;
    current := r ();
    Printf.printf "NEXT %d\n" !current;    
    incr i;
  done