 <code class="computeroutput"><span class="identifier">hold</span><span class="special">[]</span></code>
            here will make sure the changes to the attribute caused by the (failing)
            first alternative will not be visible after the whole parsing succeeded.
          </p>
<p>
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="spe