span class=keyword>return </span><span class=identifier>e1</span><span class=special>.</span><span class=identifier>id</span><span class=special>&lt;</span><span class=identifier>x</span><span class=special>;}
  </span><span class=special>};

  </span><span class=keyword>friend </span><span class=identifier>std</span><span class=special>::</span><span class=identifier>ostream</span><span class=special>&amp; </span><span class=keyword>operator</span><span class=special>&lt;&lt;(</span><span class=identifier>