Re: Range Types: << >> -|- ops vs empty range

Jeff Davis  wrote:
> ">>" means "strictly right of"
> "<<" means "strictly left of"
> "-|-" means "adjacent" (touching but not overlapping)
> 
> I'm open to suggestion about how those behave with empty ranges.
OK, that still leaves a lot to the imagination, though.  To try to
clarify in *my* mind:
"empty range"
=============
Zero length? If so, is it fixed at some point, but empty?   '(x,x)'?   '[x,x)'?
Is it everything? '[-inf,+inf]'?
Is it really meaningfully distinct from NULL?
Where do you see it being useful?
-Kevin