   and <code class="computeroutput"><span class="identifier">errno_on_erro</span></code> policies,
      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 policy for this function is <code class="computeroutput"><span class="identifier">ignore_error</span></code>:
      note that this error type is reserved for situations whe