> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">const</span> <span class="identifier">DATA_TYPE</span> <span class="special">&amp;</span><span class="identifier">x</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">{</span>
    <span class="keyword">return</span> <span class="identifier">first_name_offset</span> <span class="special">+</span> <span class="identifier">x</span><span class="special">.</span><span class="ide