C++ Template Classes

Question

I'm a Computer Science student and we're currently studying C++ Templates . We were instructed to write a Linked List template class and we are not allowed to use STL (note that this is unfinished code):

template <class T>
class LinkedList
{
private:
    //////// NODE CLASS //////////
    template <class T>
    class Node
    {
    public:
        ///// DATA MEMBERS
        T *m_val;
        Node<T> *m_next;
        Node<T> *m_prev;
        // CTORS
        Node(T *val) : m_val(val) { m_next = NULL;  m_prev = NULL; }
        Node(T *val, Node<T> *next, Node<T> *prev) : m_val(val), m_next(next), m_prev(prev) { }
        // C.CTOR
        Node(const Node<T> & n) { m_val = n->m_val; m_next = n->m_next; m_prev = n->m_prev; }
        // DTOR
        ~Node() { delete m_val; if (m_prev) m_prev->m_next = m_next; if (m_next) m_next->m_prev = m_prev; }
    };
    ///////////////////////

    Node<T> *first;
public:
    LinkedList(T*)
    {

    }
    ~LinkedList();
};

template <class T>
LinkedList<T>::LinkedList(T* t)
{
    first = Node<T>(t); /// <---- PROBLEM HERE
}

However, the problem is that the compiler doesn't let me use the Node Constructor..

What am I doing wrong?

EDIT:

As I said, this is unfinished code, so I thought the error I'm getting would be confusing (because I couldn't see directly where the problem comes from).

Anyway, Here is the error (Debugging on Microsoft Visual C++ 2010 Express):

1>------ Build started: Project: Ex4, Configuration: Debug Win32 ------
1>MSVCRTD.lib(crtexe.obj) : error LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup
1>c:\users\dan\documents\visual studio 2010\Projects\Ex4\Debug\Ex4.exe : fatal error LNK1120: 1 unresolved externals
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Answer 1

The line

first = Node<T>(t);

needs to be

first = new Node<T>(t);

since first is a Node* , not a Node .

You can also initialize it using:

template <class T>
LinkedList<T>::LinkedList(T* t) : first(new Node<T>(t))
{
}

which is a preferred approach.