value</em></span>: users that
        want to pass function objects with internal state might want to use <a href="../../../../../../doc/html/ref.html" target="_top">Boost.Ref</a> to wrap the object
        so that it's passed by reference.
      </p>
<p>
        <span class="bold"><strong>Requires</strong></span>: that the match_results object
        has been initialized as a result of a successful call to <a class="link" href="regex_search.html" title="regex_search"><code class="computeroutput"><span cla