>> Because intervals (mathematical not SQL) can be open or closed at each
>> end point we need to know what the next an previous value would be at
>> the specified granularity. And while you can do some operations without
>> knowing this, there are many you can't. For instance you could not tell
>> whether two [] or () ranges were adjacent, or be able to coalesce an
>> array of ranges.
>
> This statement seems to me to demonstrate that you don't actually
> understand the concept of open and closed ranges. It has nothing
> whatsoever to do with assuming that the data type is discrete;
> these concepts are perfectly well defined for the reals, for example.
> What it is about is whether the inclusion conditions are "< bound"
> or "<= bound".
IMHO the first question is whether, for integers, [1,2] UNION [3,5]
should be equal to [1,5]. In math this is certainly true, and defining
'next' seems like a reasonable way to establish this in postgres.
The next question is whether, for floats, [1,3-FLT_EPSILON] UNION
[3,5] should be [1,5].
And the next question is whether, for numeric(6,2), [1,2.99] UNION
[3,5] should be [1,5].
FWIW, I would answer yes, no, yes to those three questions.
-Nathan
