ss="identifier">U</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="special">{</span>
  <span class="comment">// types</span>
  <span class="keyword">typedef</span> <a class="link" href="expr.html" title="Struct template expr">proto::expr</a><span class="special">&lt;</span> <a class="link" href="tag/shift_right.html" title="Struct shift_right">proto::tag::shift_right</a><span class="special">,</span> <a class="link" href="listN.html" title="Struct template listN">proto: