1Matrix4i m = Matrix4i::Random(); 2cout << "Here is the matrix m:" << endl << m << endl; 3cout << "Here is the block:" << endl << m.block<2, Dynamic>(1, 1, 2, 3) << endl; 4m.block<2, Dynamic>(1, 1, 2, 3).setZero(); 5cout << "Now the matrix m is:" << endl << m << endl; 6