pl</span><span class="special">::</span><span class="identifier">identity</span><span class="special">&lt;</span> <span class="identifier">DataSet2</span> <span class="special">&gt;</span> <span class="special">&gt;&gt;</span><span class="special">::</span><span class="identifier">type</span> 
          <a name="boost.unit_test.data.monomorphic.operator+_idp58468896"></a><span class="keyword">operator</span><span class="special">+</span><span class="special">(</span><span class="identifier">DataSet1</span> 