     symbols, tree and utility. There is no guarantee that these directories will
        still be present in future versions of Spirit. We only keep them for backward
        compatibility. Please be warned.
      </p>
<p>
        Each directory (except include, home, and repository) has a corresponding
        header file that contains forwarding includes of each relevant include file
        that the directory contains. For example, there exists a &lt;boost/spirit/actor.hpp&gt;
        header file which 