The defining characteristic of IComparable<Thing>s is that they form a line. Intervals are subsets of this line,
as are sets consisting of a single Thing.
This project considers interval sets. An example of an interval set is
[a, b) + [c, d) + [e,e]
(where a, b, c, d and e are Things) which is the union of the set of Things that are greater than or equal to
a and less than b, the set of Things that are greater than or equal to c and less than d and the set containing only e.
Another interval set is
[b,c)
When we join these two interval sets, the result is
[a,d) + [e,e]
Similarly, when we take [a,d) and we subtract [b,c) from it, the result is [a,b) + [c,d).
See this test for an implementation of this using double as Thing