 class' public interface
      where error reporting code can do something intelligent with them. If
      you only expose a textual representation of those numbers in the
      <code>what()</code> string, you will make life very difficult for
      programmers who need to do something more (e.g. subtraction) with them
      than dumb output.</li>

      <li><b>Make your exception class immune to double-destruction</b> if
      possible. Unfortunately, several popular compilers occasionally cause
      exce