From Newsgroup: comp.lang.prolog
Hi,
My recent thinking is such rounding could have
a place in CLAM (Constraint Logic Abstract Machine),
as part of some interval arithmetic. Particularly
pointed intervals, like 145.6 is basically the
interval [145.55 .. 145.65),
including the lower bound excluding the upper bound.
The value 145.6 is associated with the interval, and
not some midpoint, has to do that the rounded value is
the associated point. So all values in the interval round to
the associated rounded value. But I didnrCOt do a thorough
research yet. It would basically give a different rationalize
and associated interval computation from input, a more business
like rationalize that requires that the number
scanner tokenizer also records the number of fractional
digits in the input. So that for example 90 and 90.0 are
not the same when it comes to rationalize and associated
interval computation from some given input.
Most fixnum rounding have midpoint = rounded value:
145.6 ~~> [145.55 .. 145.65) ~~> (145.55 + 145.65) = 145.6
90 ~~> [89.5 ..90.5) ~~> (89.5 + 90.5) = 90
But some rounding, like for example automatically
choosing a scale, i.e. going from bytes to kilo bytes,
mega bytes, giga bytes etc.., many directory listings
can do that when they show a file size,
I guess the associated intervals and
rounded values are more exotic.
Bye
Mild Shock schrieb:
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 rCLin kmrCY?
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 |u 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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