lass="bold"><strong>is</strong></span>
          an iterator</strong></span><br> <br> It's not really a very interesting
          iterator, since <code class="computeroutput"><span class="identifier">node_base</span></code>
          is an abstract class: a pointer to a <code class="computeroutput"><span class="identifier">node_base</span></code>
          just points at some base subobject of an instance of some other class,
          and incrementing a <code class="computeroutput"><span class="identifier