Question

When I run this code I get a bad_alloc error, Am I accessing the subscript operator wrong or something ? To me it makes sense that I go to the appropriate object, it gets returned and then the subscript operator should kick in ? By the way I want to use arrays and not vectors 🙂

class A{
    public:
    A(int size)
    {
        array = new int[size];
    }
    int& operator[](const int &i)
    {
        return array[i]
    }
    private:
       int * array;
};

int main()  {
   A ** a = new A*[10];
   for(int i = 0; i < 10; i++)  {
      a[i] = new A(10);
      for(int l = 0; l < 10; l++)   {
         cout << a[i][l] << endl;
      }
   }
}

Thanks in advance

Answer 1

You need to dereference the pointer before you can call operator[]

cout << (*(a[i]))[l] << endl;

Here’s what needs to happen, step by step:

A* pA = a[i];
A& rA = *pA;
int& val = rA[l];
cout << val;

Currently this happens:

A* pA = a[i];
A& ra = *(pA + l); // pA is indexed as an array of As - this is wrong
cout << ra; // invalid memory