0001 template <typename T> T& Vector<T>::operator[] ( Rank r ) //重载下标操作符 0002 { return _elem[r]; } // assert: 0 <= r < _size 0003 0004 template <typename T> const T& Vector<T>::operator[] ( Rank r ) const //仅限于做右值 0005 { return _elem[r]; } // assert: 0 <= r < _size