l">&amp;</span> <span class="special">=</span> <span class="identifier">combiner_type</span><span class="special">(</span><span class="special">)</span><span class="special">,</span> 
         <span class="keyword">const</span> <span class="identifier">group_compare_type</span><span class="special">&amp;</span> <span class="special">=</span> <span class="identifier">group_compare_type</span><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</spa