Document boxing.
Document Delay.
Style and so forth.
Sets.
Sets conform to ArrayLiteralConvertible.
Update Set.
Add the memoizing combinator.
Boxes are hashable.
Boxes are equatable.
Delays are hashable.
Delays are semi-equatable.
Alphabets must be Hashable.
Comment out intersections.
Rename Reduce to Reduction, Repeat to Repetition.
Basically Hashable languages.
None too sure how this got missed.
Memoizing fixpoint taking an initial value.