_pointer</span><span class="special">;</span> 
  <span class="keyword">typedef</span> <span class="emphasis"><em><span class="identifier">unspecified</span></em></span>                     <a name="boost.heap.skew_heap.implementation_defined.value_extractor"></a><span class="identifier">value_extractor</span><span class="special">;</span>    
  <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">array</span><span class="special">&