r library, so we will
      append UDEF_ to our identifier names to make them unique. Our udef library
      deals in geometrical shapes so we will create a user-defined subtype which
      consists of identifiers for the various shapes our udef library can manipulate
      in their macros. So our identifier registrations and pre-detections placed
      in our header file will be:
    </p>
<pre class="programlisting"><span class="preprocessor">#define</span> <span class="identifier">BOOST_VMD_REGISTER_UDEF_