the following function performs a chain at the head of the list (adds a new cell to the head) :

(we assume that the function t_cell *createCell(int); creates a new individual cell)

void addHead(t_list *p_list, int val)
{
    t_cell *new = createCell(val);
    p_list->head = new;
    new->next = p_list->head;

}