n and Test
          Program</a></li>
        </ul>
      </li>

      <li><a href="#contributors">Contributors</a></li>

      <li><a href="#old_lib_note">Note for Users of Older Versions</a></li>
    </ul>

    <h2><a name="rationale">Rationale</a></h2>

    <p>Overloaded operators for class types typically occur in groups. If you
    can write <code>x&nbsp;+&nbsp;y</code>, you probably also want to be able
    to write <code>x += y</code>. If you can write <code>x &lt; y,</code> you
    also want <code>x