ss="comment">// while instantiating the multi_pass</span>
    <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Input</span><span class="special">&gt;</span>
    <span class="keyword">struct</span> <span class="identifier">unique</span>
    <span class="special">{</span>
        <span class="comment">// these typedef's will be exposed as the multi_pass iterator</span>
        <span class="comment">// properties</span>
      