pan class="identifier">group</span>       <span class="special">::=</span> <span class="char">'('</span> <span class="identifier">expression</span> <span class="char">')'</span>
<span class="identifier">factor</span>      <span class="special">::=</span> <span class="identifier">integer</span> <span class="special">|</span> <span class="identifier">group</span>
<span class="identifier">term</span>        <span class="special">::=</span> <span class="identifier">factor</span> <span class="special">((</span><