Function print_size

doc/examples/function_taking_eigenbase.cpp:6–10

template <typename Derived>
void print_size(const EigenBase<Derived>& b)
{
  std::cout << "size (rows, cols): " << b.size() << " (" << b.rows()
            << ", " << b.cols() << ")" << std::endl;
}

int main()
{