Thread: Linked List Subtraction

I'm trying to overload the - and -= operators for use on a linked list. I need to be able to subtract two linked lists. So if, as an example, I had

Code:

{2,2,2,3,2,2,1} - {2,2,3}

I would get

Code:

{2,2,2,1}

as a result.

So far I have this as a non-member function:

Code:

bag operator -(const bag& b1, const bag& b2)
    {
        bag answer;
        
        answer -= b1; 
        answer -= b2;
        return answer;
    }

However, I am missing the member function -=. I have the += function, but I'm not sure how to do it backwards.

How should I go about doing this?