pan class="special">!=</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">birth</span><span class="special">)</span> <span class="special">{</span>
      <span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">birth</span> <span class="special">&lt;</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">birth</span><span class="special">;</span>
    <span cl