Question

I am getting this error in Visual Studio 2010 Pro: “Error C2953: ‘list_1::Node’ : class template has already been defined”

Here is my Node.cpp class list that is getting the error (on line 24, the last line of the code.)

#include "Node.h"

namespace list_1
{
    template <typename T>
    struct Node
    {
        //Constructor
        Node<T>(T D)
        {
            data = d;
            next = NULL;        
        }
    }
;}

And the Node.H file:

#pragma once

namespace list_1
{
    template <typename T>
    struct Node
    {
        T data;
        Node<T> *next;

        // Constructor
        // Postcondition: 
        Node<T> (T d);
    };
}

I already looked here, which doesn’t help me since I am already using #pragma once, and in the list header file I have #ifndef LIST_H and #define LIST_H. This question doesn’t suit my needs and everything in this answer seems to be related to having the template bit that I already have.

If I try making it struct Node I get the error “error C2753: ‘list_1::Node’ : partial specialization cannot match argument list for primary template”

So I am at a loss at what to do. Please help.

Answer 1

I agree with your compiler.. You are defining the struct twice.

To fix –

Remove from your header.

And your .cpp should look like this.

#include "Node.h"

namespace list_1
{
    //Constructor
    template<typename T>
    Node<T>::Node(T D){
        ...
    }
}

Essentially, the struct block only appears in the header.

Additionally I wonder if you are aware of the problems involving defining the template classes members in a .cpp file