ype</span><span class="special">)</span></code> macro and it's related <code class="computeroutput"><span class="identifier">has_type_InnerType</span></code>
      metafunction to determine if the nested type 'InnerType' exists. This solution
      is perfectly valid, and in conjunction with Boost MPL's selection metafunctions,
      we can do compile-time selection to generate the correct template code.
    </p>
<p>
      However this does not scale that well syntactically if we need to drill down
      fu