s are traced. This constant may be used to redefine
  this default. If this is <tt>1</tt> (<tt>true</tt>), then tracing is enabled
  by default, if this constant is <tt>0</tt> (<tt>false</tt>), the tracing is
  disabled by default. This preprocessor constant is set to <tt>1 </tt>(<tt>true</tt>)
  by default.</p>
<p>Please note, that the following <tt>BOOST_SPIRIT_DEBUG_...() </tt>macros are
  to be used at function scope only.</p>
<a name="spirit_debug_node_p_"></a>
<h3>BOOST_SPIRIT_DEBUG_NODE(p)</h3>
<p> D