 to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>
                      if a certain type, <code class="computeroutput"><span class="identifier">P</span></code>,
                      is a PrimitiveParser, <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code>
                      otherwise (See <a href="../../../../../../../../l