Re: Are range_before and range_after commutator operators?

On Thu, 2011-11-17 at 17:10 -0500, Tom Lane wrote:
> Applied, thanks. These comments aren't quite what I'd hoped for though.
> What I'm lacking is the conceptual context, ie, why is a
> less-equal-greater primitive for bounds a good thing? It seems like
> when you consider the four possible directional (lower/upper)
> combinations, the same result from range_cmp_bounds means something
> different in each case, and I find that confusing. I wonder whether
> functions defined along set-theoretic lines (this bound is strictly
> weaker or stronger than this other one, or these bounds together define
> an empty or singleton or non-singleton set) might be more transparent.

I think it comes down to how helpful it is to define higher-level
functions in terms of range_cmp_bounds versus some other function (or
set of functions).

range_cmp_bounds seemed to work out fairly well for most of the
operators, and it was the best that I came up with. The nice thing about
it is that it can compare a lower bound to another lower bound, or to an
upper bound. Then again, perhaps I tried to hard to unify those
concepts, and it just led to complexity?

I'm open to suggestion.

Regards,
Jeff Davis