////   This file contains the C++ code from Program 4.20 of//   "Data Structures and Algorithms//    with Object-Oriented Design Patterns in C++"//   by Bruno R. Preiss.////   Copyright (c) 1998 by Bruno R. Preiss, P.Eng.  All rights reserved.////   http://www.pads.uwaterloo.ca/Bruno.Preiss/books/opus4/programs/pgm04_20.cpp//template <class T>class Array2D{protected:    unsigned int numberOfRows;    unsigned int numberOfColumns;    Array<T> array;public:    class Row    {	Array2D& array2D;	unsigned int const row;    public:	Row (Array2D& _array2D, unsigned int _row) :	    array2D (_array2D), row (_row) {}	T& operator [] (unsigned int column) const	    { return array2D.Select (row, column); }    };    Array2D (unsigned int, unsigned int);    T& Select (unsigned int, unsigned int);    Row operator [] (unsigned int);};