s="special">|</span> <span class="special">(</span><span class="char">'-'</span> <span class="identifier">term</span><span class="special">))*</span>
</pre>
<p>
      is approximated using facilities of Spirit's <span class="emphasis"><em>Qi</em></span> sublibrary
      as seen in this code snippet:
    </p>
<pre class="programlisting"><span class="identifier">group</span>       <span class="special">=</span> <span class="char">'('</span> <span class="special">&gt;&gt;</span> <span class="identifier">expres