 example <code class="computeroutput"><span class="special">[[:</span><span class="identifier">lower</span><span class="special">:]]</span></code> matches any lower case character. See
        <a class="link" href="character_classes.html" title="Character Class Names">character class names</a>.
      </p>
<h6>
<a name="boost_regex.syntax.basic_extended.h13"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_extended.collating_elements"></a></span><a class="link" href="basic_extended.html#bo