c++ type traits

// 移除引用获取原始类型
template <typename _Tp>
struct remove_reference
{
    typedef _Tp type;
};

template <typename _Tp>
struct remove_reference<_Tp &>
{
    typedef _Tp type;
};

template <typename _Tp>
struct remove_reference<_Tp &&>
{
    typedef _Tp type;
};