can I use SFINAE to selectively define a member variable in a template class?

Question

So what I want to do is to create a template class which may or may not contain a member variable based on the template argument passed in. like following:

t         


        

Answer 1

#pragma once
#include 

template 
class Node;


template 
class Node>
{
public:
    Node(const T& v) : value(v) {}

private:
    T value;
    Node* next = nullptr;
};

template 
class Node>
{
public:
    Node(const T& v) : value(v) {}

private:
    T value;
    Node* next = nullptr;
    Node* prev = nullptr;
};

Single or double linked list node based on boolean flag