     </P>
      </BLOCKQUOTE>
      <P>
      <P>In Boost.Regex each sub-expression match is represented by a <A href="sub_match.html">
            sub_match</A> object, this is basically just a pair of iterators denoting 
         the start and end possition of the sub-expression match, but there are some 
         additional operators provided so that objects of type sub_match behave a lot 
         like a std::basic_string: for example they are implicitly <A href="sub_match.html#m3">
            converti