n> <span class="identifier">C</span><span class="special">,</span> <span class="identifier">R</span><span class="special">,</span> <span class="identifier">D</span><span class="special">&gt;</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">y</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>

 <span class="keyword">private</span><span class="special">:</span>
    <span class="identifier">Base</span> <span 