n>
      <span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">use_default</span>              <span class="comment">// Value</span>
      <span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">forward_traversal_tag</span>    <span class="comment">// CategoryOrTraversal</span>
    <span class="special">&gt;</span>
<span class="special">{</span>
 <span class="keyword">pri