multiplying vectors in eigen code example

Example 1: transpose matrix eigen c++

MatrixXcf a = MatrixXcf::Random(2,2);
cout << "Here is the matrix a\n" << a << endl;
 
cout << "Here is the matrix a^T\n" << a.transpose() << endl;

Example 2: matrix multiplication c++ eigen

Matrix2d mat;
  mat << 1, 2,
         3, 4;
  std::cout << "Here is mat*mat:\n" << mat*mat << std::endl;