xotic such as a Unicode character type.
      </p>
<a name="boost_regex.match_results.str"></a><pre class="programlisting"><span class="identifier">string_type</span> <span class="identifier">str</span><span class="special">(</span><span class="keyword">int</span> <span class="identifier">sub</span> <span class="special">=</span> <span class="number">0</span><span class="special">)</span><span class="keyword">const</span><span class="special">;</span>
<span class="identifier">string_type</span> <span class=