definition des methodes dans list.c

	return l==NULL;

}

/*list_t list_push(list_t l, void* x){

list_t list_push(list_t l, void* x){

	list_t N = malloc(sizeof(struct cell_t));

	N->val = x;

	N-> next = l;

	if (list_is_empty(l))		

		N->id = 1;

	else

		N->id = l->id + 1;

	return N ;

}

list_t list_tail(list_t l){

	return l->next;

}

void* list_pop(list_t* l){ 

	list_t tmp= (*l)->next;

	void * v = (*l)->val;

	free(*l);

	*l = tmp;

	return v;

}

void* list_top(list_t l){

	return l->val;

}

void list_destroy(list_t l, void (*free)(void*)){

void list_destroy(list_t l, void (*free_void)(void*)){

	while(!list_is_empty(l))

		free_void(list_pop(&l));

}

// return the found element or NULL

void* list_in(list_t l, void* x, int (*eq)(void*, void*)){

	if(list_is_empty(l))

		return NULL;

	while( ! list_is_empty(l)){

		if((eq) (l->val ,x))

			return l->val;

		else

			l=l->next;

	}

	return NULL;

}

unsigned long int list_len(list_t l){

	unsigned long int taille;

	if (list_is_empty(l))

		return 0;

	else

		return l->id;

}

*/