ctai_srting_to_int_3.cpp

template <int sign, int current_val, char current_char, char ...chars>
struct string_to_int_impl<string<'-', current_char, chars...>, sign, current_val>
{
    static constexpr auto nex_val = current_val * 10 + (current_char - '0');
    static constexpr auto value = string_to_int_impl<string<chars...>, -1, nex_val>::value;
};