atch_flag_type</span> <span class="identifier">flags</span> <span class="special">=</span> <span class="identifier">format_default</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
   <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">Formatter</span><span class="special">&gt;</span>
   <span class="identifier">string_type</span> <a class="link" href="match_results.html#boost_r