////   This file contains the C# code from Program 14.13 of//   "Data Structures and Algorithms//    with Object-Oriented Design Patterns in C#"//   by Bruno R. Preiss.////   Copyright (c) 2001--2002 by Bruno R. Preiss, P.Eng.  All rights reserved.////   http://www.brpreiss.com/books/opus6/programs/pgm14_13.txt//public sealed class RandomNumberGenerator{    private static int seed = 1;    private const int a = 16807;    private const int m = 2147483647;    private const int q = 127773;    private const int r = 2836;    private RandomNumberGenerator()	{}    public static int Seed    {	get { return seed; }	set	{	    if (value < 1 || value >= m)		throw new ArgumentException("invalid seed");	    seed = value;	}    }    public static double Next    {	get	{	    seed = a * (seed % q) - r * (seed / q);	    if (seed < 0)		seed += m;	    return (double)seed / (double)m;	}    }    // ...}