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Can CLAM do bidrectional rounding? (Was: Australian Longest Straight Road in Prolog)

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The conversion factor in the units database is:

?- qeval(X*1 is mi/km).
X = 1.609344.

I had first used 1.60934, but then used
1.609344. But I think this here is not a
symmetric answer, and a symmetric answer
using constraint logic programming

maybe impossible:

?- qeval((145.6*km =:= 90*usc:mile+quantity Eps, SIEps is Eps in km)).
Eps = 0.4716455897558234*kind_of(isq:length)[usc:mile],
SIEps = 0.7590399999999958*kind_of(isq:length)[si:kilo(si:metre)].

Do you have intervals associated with
units, so you can write “in km”?

I computes 145.6*km - 90*mile in terms of km, so it computes:

/* Windows 11 Calcultator */
145.6 - 90*1.609344 = 0.75904

/* SWI-Prolog Evaluator */
?- X is 145.6 - 90*1.609344.
X = 0.7590399999999988

So to be correctly rounded to one digit after
the period, the eps would need to be smaller. But for
the other direction, whether the conversion
from km to mile was correct, I guess a

2nd query would be needed. But still I would
be interested whether constraint logic programming
can answer such questions in one query, like
whether CLAM (the idea of Constraint Logic

Abstract Machines) has a rounding bidirectionality?
Giving new momentum to the dream that
CLAM is a silver bullet.

Mild Shock schrieb:
> Do these units packages define rounding? Is this correct:
> 
> https://www.shutterstock.com/de/image-photo/road-sign-longest-straight-australia-548866177 
> 
> 
> I think one way its correct:
> 
> 145.6 km ÷ 1.609344 km/mile = 90.47 miles
> 
> The other way its incorrect:
> 
> 90 miles × 1.609344 km/mile = 144.84 km
> 
> Mild Shock schrieb:
>> Hi,
>>
>> So how does academic purity compare to industrial
>> success? Well this talk by Martin Odersky has some
>> interesting slides comparing past and present:
>>
>> Evolving Scala by Martin Odersky | Scalar Conference 2025
>> https://www.youtube.com/watch?v=DI0NOh9r1f8
>>
>> Where Scala ranked in 2014, versus where Scala
>> ranks in 2025. Haskell gone, Clojure gone.
>>
>> LoL
>>
>> Bye

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comp.lang.prolog Frequently Asked Questions Markus Triska <triska@logic.at> - 2024-11-16 05:58 +0000
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          Australian Longest Straight Road in Prolog (Was: Clojure hasn't gained momentum [Martin Odersky 2025 Talk]) Mild Shock <janburse@fastmail.fm> - 2025-07-14 16:11 +0200
            Can CLAM do bidrectional rounding? (Was: Australian Longest Straight Road in Prolog) Mild Shock <janburse@fastmail.fm> - 2025-07-14 16:15 +0200
              Pointed intervals to the rescue [Make CLAM great again] (Was: Can CLAM do bidrectional rounding?) Mild Shock <janburse@fastmail.fm> - 2025-07-15 01:26 +0200
                Corr. Re: Pointed intervals to the rescue [Make CLAM great again] (Was: Can CLAM do bidrectional rounding?) Mild Shock <janburse@fastmail.fm> - 2025-07-15 01:28 +0200
        Sleepy Joe SWI-Prolog still waiting for a PR (Was: Prolog can keep up with the AI Boom [Forget about CLAM]) Mild Shock <janburse@fastmail.fm> - 2025-11-12 01:26 +0100
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      ANN: Go Fund Me for ISO Core Standard of Prolog (Re: Is ISO itself not simply a dialect?) Mild Shock <janburse@fastmail.fm> - 2025-10-09 18:10 +0200
        Fuck Around and Find Out : SWI-Prolog Forum [Newline FAFO] (Was: ANN: Go Fund Me for ISO Core Standard of Prolog) Mild Shock <janburse@fastmail.fm> - 2025-10-10 09:36 +0200
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    ECliPSe Prolog not a SuperProlog (Was: There is something like SuperPrologs ? [SWI, ECLiPSe, etc..]) Mild Shock <janburse@fastmail.fm> - 2025-08-06 08:30 +0200

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