class="computeroutput"><span class="identifier">_val</span></code> is another <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>
              placeholder representing the rule's synthesized attribute.
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">eps</span></code> is a special spirit
              parser that consumes no input but is always successful. We use it to
              initialize <code class