Circular Doubly Linked list

[mcoder]

My problem is to add game score (i.e. player's name & score) into a circular doubly linked list.

Now I want to add a node after the cursor of the circular doubly linked list. But I'm getting error to implement my 'add' function. Error message states that 'n' & 's' was not declared in this scope. Ya I know, it wasn't declared. But how could I pass these two values (name & score)? Any suggestion would be appreciable.

Thanks in advance.

class GameEntry {
    public:
        GameEntry( const string& n="", int s=0 );
    private:
        string name;
        int score;
        GameEntry* prev;
        GameEntry* next;

        friend class CircularDoublyLinkedList; // provide CircularDoublyLinkedList access
};

GameEntry::GameEntry( const string& n,  int s): name(n), score(s)
{

}

// a circular-doubly linked list
class CircularDoublyLinkedList {
    public:
        CircularDoublyLinkedList(); // constructor
        ~CircularDoublyLinkedList(); // destructor
        bool empty() const; // is list empty?
        const GameEntry& front() const; // element at cursor
        const GameEntry& back() const; // element following cursor
        void advance(); // advance cursor
        void add(const GameEntry& e); // add after cursor
        void remove(); // remove node after cursor
    private:
        GameEntry* cursor; // the cursor
};


CircularDoublyLinkedList::CircularDoublyLinkedList() // constructor
: cursor(NULL)
{

}

CircularDoublyLinkedList::~CircularDoublyLinkedList() // destructor
{
    while (!empty())
        remove();
}

bool CircularDoublyLinkedList::empty() const // is list empty?
{
    return cursor == NULL;
}

const GameEntry& CircularDoublyLinkedList::back() const // element at cursor
{
    return *cursor;
}

const GameEntry& CircularDoublyLinkedList::front() const // element following cursor
{
    return *cursor->next;
}

void CircularDoublyLinkedList::advance() // advance cursor
{
    cursor = cursor->next;
}

void CircularDoublyLinkedList::add(const GameEntry& e) 
{ // add after cursor
    GameEntry* u = new GameEntry;
    u->name = n;
    u->score = s;

    if(cursor == NULL)
    {
        u->next = u;
        cursor = u;
    }
    else
    {
        u->next = cursor->next;
        cursor->next = u;
    }

}

[GReaper]

Firstly, you need to understand that a circular doubly linked list never has a NULL next or prev pointers. You initialise a node by setting both pointers equal to the address of the node itself, then when you want to merge it with a list you do:

firstNode->prev->next = newNode->prev;
newNode->prev->prev = firstNode->prev;
firstNode->prev = newNode;
newNode->next = firstNode;

There are of course many ways to do this.

EDIT: This way, two lists can also be merged without any modification of the code.