黑洞迭代器

template<typename T>
class BlackHoleIterator :public iterator<output_iterator_tag,T>
{
    typedef BlackHoleIterator<T> _Self;
public:
    _Self &operator*(){return *this;}
    _Self &operator++(){return *this;}
    _Self &operator++(int){return *this;}
    _Self &operator=(const T &){return *this;}
};