//
//   This file contains the C# code from Program 4.9 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/pgm04_09.txt
//
public abstract class Matrix
{
    public abstract double this[int i, int j] { get; set; }
    public abstract int Rows { get; }
    public abstract int Columns { get; }
    public abstract Matrix Transpose { get; }
    public abstract Matrix Plus(Matrix matrix);
    public abstract Matrix Times(Matrix matrix);
    public static Matrix operator +(Matrix m1, Matrix m2)
	{ return m1.Plus(m2); }
    public static Matrix operator *(Matrix m1, Matrix m2)
	{ return m1.Times(m2); }
    // ...
}