class LLint
{ protected:
    struct link ... as before

    link * first, * last;

  public:
    LLint()
    { first = NULL;
      last = NULL; }

    void add_to_front(int newval)
    { if (first == NULL)
      { first = new link(newval, NULL);
        last = first; }
      else
        first = new link(newval, first); }

    void add_to_end(int newval)
    { if (first == NULL)
      { first = new link(newval, NULL);
        last = first; }
      else
      { link * newlink = new link(newval, NULL);
        last->next = newlink;
        last = newlink; } };

    int remove_front()
    { assert(first != NULL);
        OR
      if (first == NULL)
      { cerr << "remove from empty list\n");
        exit(1); }
      int val = first->data;
      link * old = first;
      first = first->next;
      delete old;
      if (first == NULL)
        last = NULL;
      return val; }


-----------------------------------


    void selection_sort()
    { link * begin = first;
      while (begin != NULL)
      { link * smallest = begin;
        link * ptr = begin->next;
        while (ptr != NULL)
        { if (ptr->data < smallest->data)
            smallest = ptr;
          ptr = ptr->next; }
        swap(begin->data, smallest->data);
        begin = begin->next; } }