span>
<span class="keyword">class</span> <span class="identifier">RingIteratorImpl</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">iterator_facade</span><span class="special">&lt;</span>
        <span class="identifier">RingIteratorImpl</span><span class="special">&lt;</span><span class="identifier">I</span><span class="special">,</span><span class="identifier">R</span><span class="special"