span class="identifier">combiner_type</span><span class="special">;</span>              
  <span class="keyword">typedef</span> <span class="identifier">Group</span>                                                                              <a name="boost.signals2.signal.group_type"></a><span class="identifier">group_type</span><span class="special">;</span>                 
  <span class="keyword">typedef</span> <span class="identifier">GroupCompare</span>                                                 