entifier">DescriptorT</span><span class="special">,</span> <span class="identifier">ActorT</span> <span class="special">&gt;</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">,</span> <span class="identifier">DescriptorT</span> <span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span> 
  <a name="idm23112-bb"></a><span class="keyword">operator</span><span class="special">[</span><span class="special">]</span><span 