Do you have any reference that gcd is applicable beyond the context of
inregers?
On Sat, May 16, 2020 at 5:19 PM Hauke Rehr <hauke.r...@uni-jena.de> wrote:
> wrong.
>
> first, gcd is a general concept, it’s nothing crafted but found
> it was always there and not meant for anything in the first place
> it applies to rational numbers just as fine and to any scaling
> thereof. Mathematically, you get sane results working with gcd
> on √2*ℚ, for example.
>
> second, the only if part is badly wrong, too.
> +./ (, -) a
> will work no matter a’s representation and not give an epsilon
> (unless a an epsilon :-) to start with)
>
> Am 16.05.20 um 08:26 schrieb Raul Miller:
> > GCD is meant for exact numbers.
> >
> > It works fine with fractions, IF (and only if) the numbers you are
> > working with exactly represent the numbers you intend to manipulate.
> > For binary floating point numbers this would be sums of powers of 2
> > which do not exceed the precision of the representation (for current J
> > on 64 bit machines: all divisors have to be powers of 2, you have 53
> > bits of mantissa to work with and a limited range of exponents).
> >
> > 5r2 +. 7r2
> > 1r2
> > 2.5 +. 3.5
> > 0.5
> >
> > Thanks,
> >
> >
> > --
> > Raul
> >
> > On Fri, May 15, 2020 at 11:17 PM bill lam <bbill....@gmail.com> wrote:
> >>
> >> Yes I agree GCD meant for whole numbers, so that +. on floating points
> can
> >> first convert to rational first and convert back to float afterwards
> >> +./&.x: 4.57 4.34 4.44
> >> 0.01
> >> x: is clever enough to find the shortest form of rational equal to the
> >> original floating number range
> >> (3!:3) 4.5700000000000003
> >>
> >> e300000000000000
> >> 0800000000000000
> >> 0100000000000000
> >> 0000000000000000
> >> 48e17a14ae471240
> >> (3!:3) 4.57
> >> e300000000000000
> >> 0800000000000000
> >> 0100000000000000
> >> 0000000000000000
> >> 48e17a14ae471240
> >> x: 4.5700000000000003
> >> 457r100
> >> x: 4.57
> >> 457r100
> >>
> >> That said, I don't see any real benefit for change, if a user want
> rational
> >> number behavior, he/she can use the form
> >> +./&.x:
> >>
> >>
> >>
> >> On Sat, May 16, 2020 at 7:18 AM Devon McCormick <devon...@gmail.com>
> wrote:
> >>
> >>> Since, AFAIK, GCD was originally defined in the context of whole
> numbers,
> >>> you probably get what you deserve using it with non-integers.
> >>>
> >>> On Fri, May 15, 2020 at 7:04 PM Raul Miller <rauldmil...@gmail.com>
> wrote:
> >>>
> >>>> It is odd, though, that even with comparison tolerance set to zero, +.
> >>>> is not associative on fractional floating point values:
> >>>>
> >>>> 9!:19]0
> >>>>
> >>>> 0j16":,.+./4.57 4.34 4.44
> >>>> 0.0000000000000036
> >>>> 0j16":,.+./|.4.57 4.34 4.44
> >>>> 0.0000000000290870
> >>>>
> >>>> It is commutative though:
> >>>> (-:|:)+./@>{;~4.57 4.34 4.44
> >>>> 1
> >>>> 0j16":+./@>{;~4.57 4.34 4.44
> >>>> 4.5700000000000003 0.0100000000000655 0.0099999999999758
> >>>> 0.0100000000000655 4.3399999999999999 0.0200000000000466
> >>>> 0.0099999999999758 0.0200000000000466 4.4400000000000004
> >>>>
> >>>> I'm not quite sure what's going on here... maybe a built in epsilon
> >>>> which is independent of comparison tolerance?
> >>>>
> >>>> Thanks,
> >>>>
> >>>> --
> >>>> Raul
> >>>>
> >>>> On Fri, May 15, 2020 at 6:53 PM Hauke Rehr <hauke.r...@uni-jena.de>
> >>> wrote:
> >>>>>
> >>>>> In case you are willing to accept labelling it a problem.
> >>>>>
> >>>>> As I mentioned by altering the thread’s subject, yes,
> >>>>> this ain’t a bug. But there may be an opportunity for
> >>>>> improvement without sacrifice. Or so do I think.
> >>>>>
> >>>>>
> >>>>> Am 16.05.20 um 00:49 schrieb 'Michael Day' via Programming:
> >>>>>> Not a new "bug" - I've still got J503 for some reason - so:
> >>>>>>
> >>>>>> +./4.57 4.34 4.44
> >>>>>> 5.39568e_12
> >>>>>>
> >>>>>> ABOUTJ_jijs_ NB. nearest thing to JVERSION???
> >>>>>> Copyright 1994-2004 Jsoftware Inc.
> >>>>>> For information about this and related products:
> >>>>>>
> >>>>>> Jsoftware Inc.
> >>>>>> P.O. Box 330
> >>>>>> Excelsior, MN 55331
> >>>>>> tel: 952 470-7345 fax: 952 470-9202
> >>>>>> www.jsoftware.com
> >>>>>> i...@jsoftware.com
> >>>>>>
> >>>>>> As Devon and Henry suggest, it's the usual problem with "exact"
> >>>>>> representation of reals.
> >>>>>>
> >>>>>> Mike
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> On 15/05/2020 15:17, 'Bo Jacoby' via Programming wrote:
> >>>>>>> +./4.57 4.34 4.44
> >>>>>>> 5.39568e_12
> >>>>>>>
> >>>>>>> NB. this was not the correct answer. A bug?
> >>>>>>>
> >>>>>>> +./x:4.57 4.34 4.44
> >>>>>>>
> >>>>>>> 1r100
> >>>>>>>
> >>>>>>> NB. this was a work-around
> >>>>>>> Thanks!
> >>>>>>> Bo.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>> ----------------------------------------------------------------------
> >>>>>>> For information about J forums see
> >>>> http://www.jsoftware.com/forums.htm
> >>>>>>
> >>>>>
> >>>>> --
> >>>>> ----------------------
> >>>>> mail written using NEO
> >>>>> neo-layout.org
> >>>>>
> >>>>>
> ----------------------------------------------------------------------
> >>>>> For information about J forums see
> http://www.jsoftware.com/forums.htm
> >>>> ----------------------------------------------------------------------
> >>>> For information about J forums see
> http://www.jsoftware.com/forums.htm
> >>>>
> >>>
> >>>
> >>> --
> >>>
> >>> Devon McCormick, CFA
> >>>
> >>> Quantitative Consultant
> >>> ----------------------------------------------------------------------
> >>> For information about J forums see http://www.jsoftware.com/forums.htm
> >>>
> >> ----------------------------------------------------------------------
> >> For information about J forums see http://www.jsoftware.com/forums.htm
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
> >
>
> --
> ----------------------
> mail written using NEO
> neo-layout.org
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
