获取元组元素类型的索引?

And how to get the index of a element type?

template<class T, class Tuple>
struct Index
{
    enum {value = ?;}
};

谢谢.

推荐答案

template <class T, class Tuple>
struct Index;

template <class T, class... Types>
struct Index<T, std::tuple<T, Types...>> {
    static const std::size_t value = 0;
};

template <class T, class U, class... Types>
struct Index<T, std::tuple<U, Types...>> {
    static const std::size_t value = 1 + Index<T, std::tuple<Types...>>::value;
};

在 Coli 现场观看.