Interval implements a Comparable interval [begin, end) TODO: support different sorts of intervals: (a,b), [a,b], (a, b].

IntervalTree represents a (mostly) textbook implementation of the "Introduction to Algorithms" (Cormen et al, 2nd ed.) chapter 13 red-black tree and chapter 14.3 interval tree with search supporting "stabbing queries".

Comparable is an interface for trichotomic comparisons.

InternalVisitor is used on tree searchs; return false to stop searching.

StringAffineComparable treats "" as > all other strings.