Data Structures, Algorithms, & Applications in C++
Chapter 5, Exercise 7

The code is given below and in the file arrayListWithOverloadIndex.h. Test code is included in arrayListWithOverloadIndex.cpp. 
template<class T>
class arrayListWithOverloadIndex : public arrayList<T> 
{
   public:
      // constructor and destructor
      arrayListWithOverloadIndex(int initialCapacity = 10)
           : arrayList<T> (initialCapacity) {}

      T& operator[](int);
};

template<class T>
T& arrayListWithOverloadIndex<T>::operator[](int theIndex)
{// Return a reference to position theIndex of the list.

    checkIndex(theIndex);
    return element[theIndex];
}