text: MatrixXi mat(3,3);
  mat << 1, 2, 3,   4, 5, 6,   7, 8, 9;
  cout << "Here is the matrix mat:\n" << mat << endl;
  
  // This assignment shows the aliasing problem
  mat.bottomRightCorner(2,2) = mat.topLeftCorner(2,2);
  cout << "After the assignment, mat = \n" << mat << endl;
  