Topspeed_JPI/TS/MODBASE/RAND.MOD

(*# check(stack=>off,
          index=>off,
          range=>off,
          overflow=>off,
          nil_ptr=>off) *)
IMPLEMENTATION MODULE Rand;
(******************************************************************************)
(*       Modify by John McMonagle 4/19/88                                    *)
(*       MODULA-2    Library                                                  *)
(*                                                                            *)
(*              LOGITECH SA,   CH-1111 Romanel    (Switzerland)               *)
(*              LOGITECH Inc,  Fremont, CA 94555  (USA)                       *)
(*                                                                            *)
(*       Module  :    Random, random number generator                         *)
(*                                                                            *)
(*       Release :    3.0 - July 87                                           *)
(*                                                                            *)
(*       Copyright (C)  1987 Logitech, All rights reserved                    *)
(*                                                                            *)
(*       Permission is hereby granted to registered users to use or abstract  *)
(*       the following program in the implementation of customized versions.  *)
(*       This permission does not include the right to redistribute the       *)
(*       source code of this program.                                         *)
(*                                                                            *)
(******************************************************************************)

(*----------------------------------------------------------------------------
         Algorithm: Additive congruential method (D.Knuth)
----------------------------------------------------------------------------*)
(*/NOCHECK:O *)
  FROM EnvironUtils IMPORT
    GetTime;
  FROM NumTypes IMPORT
    Real8;

  CONST
    C  = 53;(* was54 *)
    R  = 65536.0;

  VAR
    a    : ARRAY [0 .. C] OF CARDINAL;
    j, k : [0 .. C];


  PROCEDURE Next (): CARDINAL;
    BEGIN
      INC(a [k], a [j]);

      IF k = 0 THEN
        k := C;
      ELSE
        DEC(k);
      END;
      IF j = 0 THEN
        j := C;
      ELSE
        DEC(j);
      END;

      RETURN a [k];
    END Next;

  PROCEDURE RandomInit (seed : CARDINAL);
    VAR
      i, dummy : CARDINAL;
    BEGIN
      j := 23;(* was 24 *)
      k := 0;
      FOR i := 0 TO C DO
        a [i] := 0;
      END;
      a [k] := 31415 + seed;
      IF a [k] = 0 THEN
        a [k] := 31415;
      END;
      (* added 4/19/88  make sure seed is odd or all will be even *)
      IF NOT ODD(a[k])
      THEN
         INC(a[k]);
      END;
      FOR i := 0 TO 1219 DO(* was 1999 reduced as precision is not required *)
        dummy := Next ();
      END;
    END RandomInit;

  PROCEDURE RandomCard (bound : CARDINAL): CARDINAL;
    BEGIN
      IF bound = 0 THEN
        RETURN Next ();
      ELSE
        RETURN Next() MOD bound;
       (* RETURN TRUNC (FLOAT (bound) * FLOAT (Next ()) / R); *)
      END;
    END RandomCard;

  PROCEDURE RandomInt (bound : INTEGER): INTEGER;
    BEGIN
      RETURN INTEGER (RandomCard (CARDINAL (ABS (bound))));
    END RandomInt;
(*
  PROCEDURE RandomReal () : Real8;
    BEGIN
      RETURN VAL(Real8,RandomCard (10000)) * 1.0E-16 +
             VAL(Real8,RandomCard (10000)) * 1.0E-12 +
             VAL(Real8,RandomCard (10000)) * 1.0E-08 +
             VAL(Real8,RandomCard (10000)) * 1.0E-04;
    END RandomReal;

*)
  PROCEDURE Randomize;
    VAR
      minute,second,hundredths,
      i, j : CARDINAL;
      dummy: CARDINAL;
      str: ARRAY[0..40] OF CHAR;
    BEGIN
      GetTime(dummy,minute,second,hundredths,str);
      RandomInit (hundredths*second);
      j := minute;
      FOR i := 0 TO j DO
        dummy := Next ();
      END;
    END Randomize;


BEGIN
  Randomize;
 (* FOR j:=0 TO C DO
    a[j]:=0;
  END;
  j:=0;
  k:=0;	*)
END Rand.