+      +--+---+                   +-+---+      +--+---+   
                                                       |     |            |     |      |      |                   |     |      |      |   
                                                     false true         false true   false  false               false true   false  false 
</pre><p>Of course, all will be well if the content of all nodes allows these operations. If you have heterogeneous data, there <b>might</b> be errors. If you combine two tree