There are several methods on domains and related types that are not in
the language reference manual.  Many of them are obvious (e.g.,
isSubset) but a few are less obvious:

isADR() returns true iff the domain is a unit-stride rectangle or union of same
        (ADR stands for "all dense rects")

demote() attempts to "optimize" the runtime representation of a general 
         domain by merging adjacent rectangles.  (It calls joinRectangles().)