ial">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">random_access_iterator_tag</span><span class="special">,</span> <span class="identifier">R</span><span class="special">&gt;::</span><span class="identifier">difference_type</span> <span class="identifier">difference_type</span><span class="special">;</span>

<span class="keyword">private</span><span class="special">:</span>
    <span class="keyword">friend</span> <span class="keyword">class</span> <span 