d in. The value <code class="computeroutput"><span class="identifier">context</span></code>
          is used by semantic actions written using <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>
          to access various context dependent attributes and values. For more information
          about <a href="../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a>
          placeholder expressions usable in semantic actions see <a cl