>> it's only partly a separate issue. one of the sources of the problem
>> here is that half-open empty intervals don't makes sense. the question
>> "does the instant 9:00 belong to [9:00, 9:00)" has conflicting answers
>> (by definition). empty intervals that are either open or closed actually
>> do make sense. so "does the instant 9:00 belong to [9:00, 9:00]" has a
>> clear answer: "yes". "does the instant 9:00 belong to (9:00, 9:00)" also
>> has a clear answer: "no".
>
> But the analagous question is does (08:00,10:00) contain (09:00,09:00) ?
> So the same non-intuitive empty-interval logic applies.
>
i'd like to stop using the term "empty interval" because it suggests a
possibly unnecessary analogy with the empty set. i'd prefer to use the
term zero-length interval.
the zero-length interval (9:00, 9:00) is more like an empty set in that
there are no instants that belong to it. in this sense, it is similar to
the half-open zero length interval.
and you're right, (9:00, 9:00) although better behaved than [9:00,
9:00) causes similar problems when applied to interval operations. OTOH
i think [9:00, 9:00] is generally better behaved.
so here's my question: under what circumstances would [9:00, 9:00) or
(9:00, 9:00) actually be constructed / calculated? could [9:00, 9:00] be
returned in those situations instead.
regards,
al
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