用C++模板元编程实现一个编译期快速排序

好的，下面是一个使用C++模板元编程实现的编译器级别的快速排序：

#include <iostream>

template <int... Args>
struct IntList {};

template <typename List>
struct Length;

template <int Head, int... Tail>
struct Length<IntList<Head, Tail...>> {
    static const int value = 1 + Length<IntList<Tail...>>::value;
};

template <>
struct Length<IntList<>> {
    static const int value = 0;
};

template <typename List, int N>
struct Get;

template <int Head, int... Tail, int N>
struct Get<IntList<Head, Tail...>, N> {
    static const int value = Get<IntList<Tail...>, N - 1>::value;
};

template <int Head, int... Tail>
struct Get<IntList<Head, Tail...>, 0> {
    static const int value = Head;
};

template <typename List, int N>
struct Set;

template <int Head, int... Tail, int N>
struct Set<IntList<Head, Tail...>, N> {
    using type = IntList<Head, typename Set<IntList<Tail...>, N - 1>::type>;
};

template <int Head, int... Tail>
struct Set<IntList<Head, Tail...>, 0> {
    using type = IntList<0, Tail...>;
};

template <typename List, int N, int V>
struct Insert;

template <int Head, int... Tail, int N, int V>
struct Insert<IntList<Head, Tail...>, N, V> {
    using type = typename Insert<typename Set<IntList<Head, Tail...>, N>::type, N - 1, V>::type;
};

template <int V, int... Tail>
struct Insert<IntList<Tail...>, 0, V> {
    using type = IntList<V, Tail...>;
};

template <typename List>
struct QuickSort;

template <int Head, int... Tail>
struct QuickSort<IntList<Head, Tail...>> {
    using smaller = typename QuickSort<typename Insert<IntList<Tail...>, 0, Head>::type>::type;
    using larger = typename QuickSort<typename Set<IntList<Tail...>, 0>::type>::type;
    using type = typename Insert<smaller, Length<smaller>::value, Head>::type;
};

template <>
struct QuickSort<IntList<>> {
    using type = IntList<>;
};

int main() {
    using list = IntList<4, 7, 1, 9, 2, 8, 3, 6, 5>;
    using sorted_list = QuickSort<list>::type;
    std::cout << "Sorted list: ";
    for (int i = 0; i < Length<sorted_list>::value; ++i) {
        std::cout << Get<sorted_list, i>::value << " ";
    }
    std::cout << std::endl;
    return 0;
}

这个实现使用了C++11可变参数模板和递归模板特化来实现一个编译期快速排序算法。它使用IntList模板来表示整数列表，Length模板用于计算列表的长度，Get模板用于获取列表中的元素，Set模板用于设置列表中的元素，Insert模板用于将元素插入到列表中的指定位置，QuickSort模板用于实现快速排序。