Question 5:

The diameter of a tree T is the largest of the following quantities:

* the diameter of T's left subtree
* the diameter of T's right subtree
* the longest path between leaves that goes 
  through the root of T (this can be computed 
  from the heights of the subtrees of T) 


Implement the Diameter computation in a structure-shy way
using DemeterF. Do one traversal of the tree to compute
both height and diameter.

Your function object must correctly compute the diameter for both
cd-pure and cd-with noise from question 1.

Find the UNKNOWN below:

From the class dictionary:

DiameterPair = "height" <height> int "diameter" <diameter> int.


From the function object:

class Diameter extends IDba{ // type unifying 
    DiameterPair combine(BSTInt l) {return new DiameterPair(0,0);}
    UNKNOWN
}