On Mon, Jun 23, 2025 at 08:12:06AM +0200, 'Ralf Hemmecke' via FriCAS - computer
algebra system wrote:
> On 6/23/25 01:22, Waldek Hebisch wrote:
> > ATM I did not look at conditions and categories. However,
> > I have noticed a different issue. Namely, Interval is
> > supposed to be an implementation of interval artithmetic.
> > Which means that interval obtained as result of
> > interval arithmetic is supposed to contain interval
> > computed using infinitely precise artithmtic. Since
> > operations in Float are approximate it means that
> > results of arithmetic operations on intervals need to be
> > enlarged to compensate for effect of rounding. This
> > is done by use of roundUp and roundDown in qinterval.
>
> Right. That is why qInterval has no default implementation. And Interval
> does not inherit anything from AInterval only from AIntervalCategory.
> AInterval is for the exact case, Interval for Floating point intervals.
OK, your patch removes implementations of '+', '-', '*' but
defaults in AIntervalCategory call qinterval from Interval.
> > I did not check if roundUp and roundDown _always_ lead
> > to correct result, but without them results are clearly
> > incorrect.
>
> Yes. But roundUp and roundDown are implemented / used in Interval and there
> is no default package for IntervalCategory.
>
> > So, most of operations in Interval should stay the same.
>
> Yes, when I first designed AIntervalCategory, I had in mind that the
> semantics of Interval should not change. Of course, I could have made a
> mistake, but then it would have been unintentional.
>
> Maybe I should come up with a number of tests?
That is actually tricky. In case on Interval what matters are
tiny 1 bit differences which occur in special cases.
--
Waldek Hebisch
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