thm before it gives up and raises an
            <a class="link" href="error_handling.html#evaluation_error">evaluation_error</a>.
          </li>
</ul></div>
<p>
        You can control policies:
      </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            Using <a class="link" href="../policy/pol_ref/policy_defaults.html" title="Using Macros to Change the Policy Defaults">macros</a>
            to change any default policy: the is the pre