e class="computeroutput">BOOST_PROTO_ref_a(<em class="replaceable"><code>N</code></em>)</code> generates sequences like:
      </p>
<p>
        </p>
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">a</span><sub><span class="number">0</span></sub><span class="special">)</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span>