[Jprogramming] Bug: +./4.57 4.34 4.44

[bill lam]

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 <devonmcc at 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 <rauldmiller at 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.rehr at 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
> > > >     info at 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
>