 class="comment">// types</span>
  <span class="keyword">typedef</span> <a class="link" href="unit.html" title="Class template unit">unit</a><span class="special">&lt;</span> <span class="identifier">Dim</span><span class="special">,</span> <span class="identifier">System</span> <span class="special">&gt;</span> <a name="boost.units.unit.unit_type"></a><span class="identifier">unit_type</span><span class="special">;</span>     
  <span class="keyword">typedef</span> <a class="link" href="unit.html" title="C