 class="identifier">logic_error</span></code> if the match_results object
        was not initialized.
      </p>
<p>
        <span class="bold"><strong>Effects</strong></span>: Returns a reference to the <a class="link" href="sub_match.html" title="sub_match"><code class="computeroutput"><span class="identifier">sub_match</span></code></a>
        object representing the character sequence from the end of the match found
        to the end of the string being matched or searched.
      </p>
<a name="boost_