Polyhedron/external/eigen-3.4.0/doc/snippets/Tutorial_AdvancedInitialization_CommaTemporary.cpp

MatrixXf mat = MatrixXf::Random(2, 3);
std::cout << mat << std::endl << std::endl;
mat = (MatrixXf(2,2) << 0, 1, 1, 0).finished() * mat;
std::cout << mat << std::endl;