Ron: On Fri, 15 Oct 2021 at 20:16, Ron <ronljohnso...@gmail.com> wrote: > > so no overlap. > I was afraid you were going to say that. It's completely bizarre, but seems > to be a "thing" in computer science.
Right half open intervals are normally choosed because they can fully cover the real line without overlap. Full open and full closed can not. When you have timestamps, or float/doubles, you are trying to represent a point on a (time) line, although their finite computer representation is countable. When you use dates / integers you can use any kind of intervales, as they are countable, but it is easier if you use the same representation. When I do billing I select monthly CDRs in one system on a condicion on a timestamp column, {setup >= '2021-05-01' and setup<'2021-06-01'}. Another system as split date/time, and I select on that table using the same limits, { fecha >= '2021-05-01' and fecha<'2021-06-01' }. I could use a full closed interval, but half open is easier. Also, if you cover the countable set of dates with half-open intervals it has the nice property of having start-range(i)=end_range(i-1), which is much easier to program. And half open are easier to generate. If you want to generate 12 element ranges starting at 1 you can do something like for i=1 to 100 step 12 print i, i+12 which nicely lets you see they are dozens, if you use closed you need to "print i, i+11" or "print i, i+12-1". In general it is a thing because it is easier. FOS