puteroutput"><span class="identifier">Message</span></code>
      is an error message describing the problem, <code class="computeroutput"><span class="identifier">Val</span></code>
      is the value of the argument that is at a pole, and <a class="link" href="../policy.html" title="Chapter&#160;18.&#160;Policies: Controlling Precision, Error Handling etc">Policy</a>
      is the current policy in use for the function that was called.
    </p>
<p>
      The default behaviour of this function is to throw a 