identifier">element_type</span><span class="special">;</span>           <span class="comment">// The element type of the set. </span>
  <span class="keyword">typedef</span> <span class="identifier">interval_type</span>                                                <a name="boost.icl.separate_interval_set.segment_type"></a><span class="identifier">segment_type</span><span class="special">;</span>           <span class="comment">// The segment type of the set. </span>
  <span class="keyword">typedef</span> <