バイナリビットマスク定数テンプレート

cppllの件でちょいと思いついたのでやってみた。
こんなことができる：

std::cout << std::hex
    << bits<001>::value << "\n"
    << bits<010>::value << "\n"
    << bits<011>::value << "\n"
    << bits<100>::value << "\n"
    << bits<101>::value << "\n"
    << bits<110>::value << "\n"
    << bits<111>::value << "\n"
    << bits<0111>::value << "\n"
    << bits<11110111>::value << "\n"
    << bits<011110111>::value << "\n"
    << bits<1011110111>::value << std::endl;

結果：

1
2
3
4
5
6
7
7
f7
f7
2f7

実装：

template <int radix, int x, bool check>
struct nest2
{
    const static bool value = false;
};

template <int radix, int x, bool cont>
struct nest1
{
    const static bool value = (x > 2) ? false : true;
};

template <int radix, int x>
struct nest2<radix, x, true>
{
    const static bool value = nest1<radix, x / radix, (x / radix >= radix)>::value;
};

template <int radix, int x>
struct nest1<radix, x, true>
{
    const static bool value = nest2<radix, x, (x % radix < 2)>::value;
};

template <int radix, int x>
struct is_
{
    const static bool value = nest1<radix, x, (x >= radix)>::value;
};

template <typename T, int radix, char odd, unsigned int binary>
struct to_binary
{
    static const T value = to_binary<T, radix, binary % radix, binary / radix>::value << 1 | odd;
};

template <typename T, int radix, char odd>
struct to_binary<T, radix, odd, 0>
{
    static const T value = odd;
};

template <typename T, bool cond, T t_val, T f_val>
struct if_
{
    const static T value = t_val;
};

template <typename T, T t_val, T f_val>
struct if_<T, false, t_val, f_val>
{
    const static T value = f_val;
};

template <unsigned int binary, typename T = unsigned int>
struct bits
{
    static const T value = if_<
        T, is_<10, binary>::value,
        to_binary<T, 10, binary % 10, binary / 10>::value,
        to_binary<T, 8, binary % 8, binary / 8>::value>::value;
};