Overloading subscripting (C++ only)

You overload operator[] with a nonstatic member function that has only one parameter. The following example is a simple array class that has an overloaded subscripting operator. The overloaded subscripting operator throws an exception if you try to access the array outside of its specified bounds:

#include <iostream>
using namespace std;

template <class T> class MyArray {
private:
  T* storage;
  int size;
public:
  MyArray(int arg = 10) {
    storage = new T[arg];
    size = arg;
  }

  ~MyArray() {
    delete[] storage;
    storage = 0;
  }

  T& operator[](const int location) throw (const char *);
};

template <class T> T& MyArray<T>::operator[](const int location)
  throw (const char *) {
    if (location < 0 || location >= size) throw "Invalid array access";
    else return storage[location];
}

int main() {
  try {
     MyArray<int> x(13);
     x[0] = 45;
     x[1] = 2435;
     cout << x[0] << endl;
     cout << x[1] << endl;
     x[13] = 84;
  }
  catch (const char* e) {
    cout << e << endl;
  }
}

The following is the output of the above example:

45
2435
Invalid array access

The expression x[1] is interpreted as x.operator[](1) and calls int& MyArray<int>::operator[](const int).

Related information

• Array subscripting operator [ ]