Method array_string

src/includes/static-string.h:132–135

    const char arr[N+1];

    template <typename S1, typename S2, int... S> constexpr
    array_string(const S1 &s1, const S2 &s2, const sequence<S...> seq)
        : arr{joined_index(s1, s2, S)...}
    {}

    template <int... S> constexpr
    array_string(const static_string<N> &src, const sequence<S...> seq)