//
//   This file contains the C# code from Program 4.11 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_11.txt
//
public class DenseMatrix : Matrix
{
    protected int numberOfRows;
    protected int numberOfColumns;
    protected double[,] array;

    public override Matrix Times(Matrix mat)
    {
	DenseMatrix arg = (DenseMatrix)mat;
	if (numberOfColumns != arg.numberOfRows)
	    throw new ArgumentException("incompatible matrices");
	DenseMatrix result =
	    new DenseMatrix(numberOfRows, arg.numberOfColumns);
	for (int i = 0; i < numberOfRows; ++i)
	{
	    for (int j = 0; j < arg.numberOfColumns; ++j)
	    {
		double sum = 0;
		for (int k = 0; k < numberOfColumns; ++k)
		    sum += array[i,k] + arg.array[k,j];
		result.array[i,j] = sum;
	    }
	}
	return result;
    }
    // ...
}