Erorr Pow function
Big<64,42> a = "64";
std::cout << a.Pow(2) << std::endl;
I get 0 as result
Big::Pow(Big &) returns:
0 - ok
1 - carry
2 - incorrect arguments
so change your example to:
Big<1, 10> a = "64";
a.Pow(2);
std::cout << a << std::endl;