get Template 명시, enable_if_t 제거

gistfile1.cpp

#include <iostream>

template <std::size_t Idx>
struct A {
    constexpr static std::size_t idx = Idx;

    template <std::size_t Target>
    using get = std::conditional_t<Target == 0, A<Idx>, typename A<idx-1>::template get<Target-1>>;
};




template <>
struct A<0> {
    constexpr static std::size_t idx = 0;

    template <std::size_t Target>
    using get = A<0>;
};



int main() {
    std::cout << A<10>::get<4>::idx << std::endl; // print 6
}

using get = A<0>;

이부분은 목적에 맞게 변경하면 될듯