template<class T>

 class XVector {

 public:

     XVector(int cacheSize):cacheSize(cacheSize), count() {

         data = new T[cacheSize];

     }

     XVector():cacheSize(), count() {

         data = new T[cacheSize];

     }

     ~XVector() {

         delete[] data;

     }

     void push_back(T val) {

         if (count >= cacheSize) {

             cacheSize <<= ;

             T* copy = new T[cacheSize];

             memcpy(copy, data, sizeof(T) * count);

             delete[] data;

             data = copy;

         }

         data[count++] = val;

     }

     void pop_back() {

         count--;

     }

     int size() const {

         return count;

     }

     T& operator[](int index) {

         //return const_cast<T&>(operator[](index));

         return const_cast<T&>((static_cast<const XVector<T>&>(*this))[index]);

     }

     const T& operator[](int index) const {

         return data[index];

     }

 private:

     int count;

     int cacheSize;

     T *data;

 };