/wiki/Recursive_data_type" target="_top"><span class="bold"><strong>recursive data types</strong></span></a>, and C and C++ programmers
      have been using it for years to build complex data structures, like tree structures
      where a node may have an arbitrary number of children.
    </p>
<p>
      What about standard containers? Containers of incomplete types have been under
      discussion for a long time, as explained in Matt Austern's great article (<a href="http://drdobbs.com/184403814" target="