und is less verbose error messages generated from static_assert.
    </p>
<h4>
<a name="spirit.faq.h1"></a>
      <span class="phrase"><a name="spirit.faq.i_m_very_confused_about_the_header_hell_in_my_boost_spirit_directory__what_s_all_this_about_"></a></span><a class="link" href="faq.html#spirit.faq.i_m_very_confused_about_the_header_hell_in_my_boost_spirit_directory__what_s_all_this_about_">I'm
      very confused about the header hell in my boost/spirit directory. What's all
      this about?</a>
    </h