Question

I have overloaded these operators to help me traverse a doubly linked list, but have run into a small bug, and being still new to c++ I am stuck. I never accounted for it the “amount” entered in would be a negative number. So I think I need to put a check in each operator for a negative number, because it will dramatically change the way I traverse the list, example, if im pointing at node 5 and I +(-3) I would want it to move backwards three nodes, the same with the -, 5 – (-3) would be go ahead three nodes. the logic seems easy, but the syntax is confusing. Here are the operators overloaded:

template <typename T>
typename doublyLinkedList<T>::iterator doublyLinkedList<T>::iterator::operator+(const int amount) const {
    doublyLinkedList<T>::iterator tempClone(*this);
    tempClone.pastBoundary=false;
    T i;

    for(i=0; i < amount; i++)
    {   
       if(tempClone.current->forward == NULL)
       {
          tempClone.pastBoundary =true;
       }else
       {
          ++tempClone;
       }
    }

    if(tempClone.pastBoundary == true)
    {
       return *this;
    }else
    {
        return tempClone;   
    }
}
template <typename T>
typename doublyLinkedList<T>::iterator doublyLinkedList<T>::iterator::operator-(const int amount) const {
    doublyLinkedList<T>::iterator tempClone(*this);
    tempClone.pastBoundary=false;
    T i;

    for(i=0; i < amount; i++)

       {    
        if(tempClone.current->backward == NULL)
       {
          tempClone.pastBoundary =true;
       }else
       {
          --tempClone;
       }
    }


    if(tempClone.pastBoundary == true)
    {
       return *this;
    }else
    {
        return tempClone;   
    }
}

Answer 1

if(amount = (-amount)) – unless amount is 0, this is always true.

And it needs to go before the for-loop. In fact, I would probably do:

if (amount < 0) return this->operator-(-amount); 

and vise versa for the other operator.