c++模板类下标运算符重载

template<class T>class Heap{public:    void pop();    void push(T);    int top();    Heap(int s);    int size();    void MaxHeap(vector<T> &arr, const int &size, int element);    void HeapSort(vector<T>&arr, int size);    const T& operator[](int i);private:    vector <T> heap;    int Size;};const T&Heap<T>::operator[](int i){    return heap[i];}