an class="identifier">data</span> <span class="special">&amp;</span><span class="identifier">r</span><span class="special">)</span>
   <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">l</span><span class="special">.</span><span class="identifier">i_</span> <span class="special">&lt;</span> <span class="identifier">r</span><span class="special">.</span><span class="identifier">i_</span><span class="special">;</span> <span class="special">}</span>
<span class="specia