def text_to_data(self, text, elt, ps):
        '''convert text into typecode specific data.
        '''
        if text is None:
            return None
        
        m = self.lex_pattern.match(text)
        if not m:
            raise EvaluateException('Bad Gregorian: %s' %text, ps.Backtrace(elt))
        try:
            retval = _dict_to_tuple(m.groupdict())
        except ValueError, e:
            #raise EvaluateException(str(e))
            raise
        
        if self.pyclass is not None:
            return self.pyclass(retval)
        return retval