 class="special">;</span>
  <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> DescriptorT<span class="special">,</span> <span class="keyword">template</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="special">&gt;</span> <span class="keyword">class</span> ActorT<span class="special">&gt;</span> 
    <span class="identifier">result_of</span><span class="special">::</span><span class="identifier">extract</span>