Rename -and: to -concat:.
Stub in an intersection combinator.
-and:.
Tidy alternation.
Compact intersections.
Derive intersections.
Describe alternation as the union.
Describe intersection as such.
More alternation tidying.
Intersection hashes.
Intersection equality.
Intersection reducibility.
Intersection predication.
Docs.
Variadic intersection.
Intersection predicate.
Tidy delays.
Implement delay sets.

NSSet parameter class checking catches HMRDelay.
Tidy tests.
Employ delay sets.