Beipiel using

#include <iostream>
#include <vector>
 
template <class T>
using Matrix = std::vector<std::vector<T>>;
 
int main()
{
  Matrix<double> m{{1, 2, 3},  
                   {1, 4, 9},
                   {1, 8, 27}};
 
  for (auto const& line : m)
  {
    for (auto x : line)
      std::cout << x << ' ';
    std::cout << '\n';
  }
}