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Exercise 11.4
Comparable Pairs

This exercise is inspired by an example in the book by Hansen and Sestoft: C# Precisely.

Program a class ComparablePair<T,U> which implements the interface IComparable<ComparablePair<T,U>>. If you prefer, you can build the class ComparablePair<T,U> on top of class Pair<S,T> from an earlier exercise in this lecture.

It is required that T and U are types that implement Icomparable<T> and Icomparable<U> respectively. How is that expressed in the class ComparablePair<T,U>?

The generic class ComparablePair<T,U> should represent a pair (t,u) of values/objects where t is of type T and u is of type U. The generic class should have an appropriate constructor that initializes both parts of the pair. In addition, there should be properties that return each of the parts. Finally, the class should - of course - implement the operation CompareTo because it is prescribed by the interface System.IComparable<ComparablePair<T,U>>.

Given two pairs p = (a,b) and q= (c,d). p is considered less than q if a is less than c. If a is equal to c then b and d controls the ordering. This is similar to lexicographic ordering on strings.

If needed, you may get useful inspiration from the Icomparable class String<T> on the accompanying slide.

Be sure to test-drive your solution!