pend on
        the direction of approach."</em></span>
      </p></blockquote></div>
<p>
      Note that in order to support information-rich error messages when throwing
      exceptions, <code class="computeroutput"><span class="identifier">Message</span></code> must contain
      a <a href="../../../../format/index.html" target="_top">Boost.Format</a> recognised format
      specifier: the argument <code class="computeroutput"><span class="identifier">Val</span></code>
      is inserted into the error m