"></a></span><a class="link" href="basic_extended.html#boost_regex.syntax.basic_extended.single_character_character_class">"Single
        character" character classes:</a>
      </h6>
<p>
        Any escaped character <span class="emphasis"><em>x</em></span>, if <span class="emphasis"><em>x</em></span> is
        the name of a character class shall match any character that is a member
        of that class, and any escaped character <span class="emphasis"><em>X</em></span>, if <span class="emphasis"><em>x<