#include <iostream>

#include <sstream> // <-- Added

#include "Eigen/Dense"

​

using std::cout;

using std::endl;

using std::string;

using std::ostringstream; // <-- Added

using Eigen::MatrixXd;

using Eigen::EigenBase;   // <-- Added

​

template <typename Derived>

std::string get_shape(const EigenBase<Derived>& x)

{

    std::ostringstream oss;

    oss  << "(" << x.rows() << ", " << x.cols() << ")";

    return oss.str();

}

​

int main(int argc, char**argv)

{

    MatrixXd m(2, 3);

    m << 1, 2, 3, 10, 20, 30;

​

    cout << "shape: " << get_shape(m) << endl;

    // shape: (2, 3)

​

    return 0;

}