mesytec-mnode/external/taskflow-3.8.0/3rd-party/eigen-3.3.7/doc/snippets/MatrixBase_eigenvalues.cpp

MatrixXd ones = MatrixXd::Ones(3,3);
VectorXcd eivals = ones.eigenvalues();
cout << "The eigenvalues of the 3x3 matrix of ones are:" << endl << eivals << endl;