Violation d'accès lors de la lecture de l'emplacement 0x00000000.

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#ifndef _LIST_
#define _LIST_

using namespace std;
template <typename T>
struct cell 
{	
public:
	T data;
	cell<T>* next;
};


template <class T>
class Liste
{
public:
	Liste(void)
	{
		this->first=NULL;
		this->last=NULL;
		this->size=0;
	}

	Liste(const Liste<T>& list)
	{
		if (list.size != 0 && list.first != NULL)
		{
			const  cell<T> *temp = list.first;
			while (temp->next != NULL)
			{
				this->AddInQueue(temp->data);
				temp = temp->next;
			}
		}
	}

	virtual ~Liste(void)
	{
		delete(this->first);
		delete(this->last);
	}

	int GetSize()
	{
		return this->size;
	}

	void AddInHead(T t)
	{
		cell<T>* c = new cell<T>();
		c->data = t;
		c->next = this->first;
		this->first = c;
		this->size++;
	}

	void AddInQueue(T t)
	{
		cell<T>* c = new cell<T>();
		c->data = t;
		c->next = NULL;
		this->last = c;
		this->size++;
	}

	void Concat(const Liste<T>& list)
	{
		if (list.first != NULL)
		{
			const  cell<T> *temp = list.first;
			while (temp->next != NULL)
			{
				this->AddInQueue(temp->data);
				temp = temp->next;
			}
		}
	}

	T ElementAt(int pos)
	{
		if (pos > this->size)
		{
			return NULL;
		}
		else 
		{
			const cell<T> *temp = this->first;
			int cpt = 0;
			for (int i=0; i<=pos; i++)
			{
				if (i == pos)
				{
					T data = temp->data;
					return data;
				}
				else
				{
					temp = temp->next;
				}
			}
			/*while (temp->next != NULL)
			{
				if (cpt == pos)
				{
					return temp->data;
				}
				cpt++;
				temp = temp->next;
			}*/
			return -1;
		}
	}

	inline const std::ostream & operator <<(std::ostream & out)
	{
		if (this->first != NULL)
		{
			const  cell *temp = this->first;
			for (int i = 0; i < this->size; i++)
			{
				out << (int)temp->data << " - " ; 
				temp = temp->next;
			} 
		}
		return out;
	}
	
private:
	int size;
	cell<T>* first;
	cell<T>* last;
};
#endif

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include "liste.h"

using namespace std;


int main (int argc, char** argv)
{
	Liste<int>* list = new Liste<int>();
	cout << "constructeur par defaut : longueur de la liste : " << list->GetSize() <<endl;
	
	list->AddInHead(1);
	cout << "ajout en tete de '1' : longueur de la liste : " << list->GetSize() <<endl;
	cout << " contenu de la liste : " << list << endl;

	list->AddInQueue(2);
	cout << "ajout en queue de '2' : longueur de la liste : " << list->GetSize() <<endl;
	cout << " contenu de la liste : " << list << endl;

	cout << "element a la position 1 : " << list->ElementAt(1) << endl;

	Liste<int>* list1 = new Liste<int>();
	list1->AddInQueue(3);
	list1->AddInQueue(4);
	list1->AddInQueue(5);
	cout << "creation de la liste 1 contenant les elements '3,4,5'" <<endl;
	cout << " contenu de la liste : " << list1 << endl;

	list->Concat(*list1);
	cout << "concat de list(2) et list1(3) : longeur de la la liste : " << list->GetSize() << endl;
	cout << " contenu de la liste : " << list << endl;

	Liste<int>* list2 = new Liste<int>(*list);
	cout << "constructeur par recopie : longueur de la liste : " << list2->GetSize() << endl;
	cout << " contenu de la liste : " << list2 << endl;

	
	char n;
	scanf ("%c",&n);
	return 0;
}

 const  cell *temp = this->first; 

const  cell<T> *temp = this->first; 

      out << (int)temp->data << " - " ;

       out << (T)temp->data << " - " ;

    friend std::ostream& operator <<(std::ostream & out, Liste<T>& list)
    {
        if (list->ElementAt(0) != NULL)
        {
            const cell<T> *temp = list->ElementAt(0);
            for (int i = 0; i < list->GetSize(); i++)
            {
                out << (T)temp->data << " - " ;
                temp = temp->next;
            }
        }
        return out;
    }

   void aff ()
    {
        printf ("\naff:\n---\n");
        cell <T> *temp = first;
        for (int i=0; i < size; i++)
        {

            std::cout << (T)temp->data;
            temp = temp->next;
        }
        printf ("---\n");
    }

Liste()
: _first(0), _last(0), _size(0)
{
}

		if (pos > this->size)
			return NULL;
                // code

    void print(std::ostream& out)
    {
        if (list->ElementAt(0) != 0)
        {
            const cell<T> *temp = list->GetFirst();
            for (int i = 0; i < list->GetSize(); ++i)
            {
                out << temp->data << " - " ;
                temp = temp->next;
            }
        }
    }

    std::ostream& operator <<(std::ostream& out, const Liste<T>& list)
    {
        list.print(out);
        return out;
    }

#include <iostream>

class Test
{
public:
  Test()
    : _a(1), _b(2), _c(3)
  {
  }

  void print(std::ostream& out) const
  {
    out << _a << " " << _b << " " << _c;
  }
private:
  int _a;
  int _b;
  int _c;
};

std::ostream& operator<<(std::ostream& out, const Test& test)
{
  test.print(out);
  return out;
}

int main()
{
  Test test;

  std::cout << test << std::endl;

  return 0;
}