public void testOperatorOveloading()
        {
            AddMatrix m1 = new AddMatrix(10, 20, 30, 40);
            AddMatrix m2 = new AddMatrix(30, 60, 90, 10);
            AddMatrix m3 = m1 + m2;

            Console.WriteLine();
            Console.WriteLine(m1.ToString());
            Console.WriteLine(m2.ToString());
            Console.WriteLine(m3.ToString());
        }
        public static AddMatrix operator +(AddMatrix m1, AddMatrix m2)
        {
            AddMatrix result = new AddMatrix(m1.a + m2.a, m1.b + m2.b, m1.c + m2.c, m1.d + m2.d);

            return(result);
        }