 <span class="comment">// ... Some error checking here</span>

    <span class="keyword">return</span> <span class="identifier">ast</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
        Let's walk through the code.
      </p>
<p>
        First, we have some typedefs for 1) The iterator type we are using for the
        parser, <code class="computeroutput"><span class="identifier">iterator_type</span></code> and
        2) For the <code class="computeroutput"><span class="ide