Rob, To get your right answer, you have to ask the right question. It seems in your case the right question has x: and for others the right question does not.
On Thu, Sep 7, 2017 at 9:17 AM, Rob B <rb75...@me.com> wrote: > I would sooner get the right answer slowly than the wrong answer quickly. > > Regards, Rob. > > > On 7 Sep 2017, at 13:48, Raul Miller <rauldmil...@gmail.com> wrote: > > > > Those proposals would cause operations on large arrays to > > intermittently stall or spam. > > > > FYI, > > > > -- > > Raul > > > > > >> On Thu, Sep 7, 2017 at 7:54 AM, Rob B <rb75...@me.com> wrote: > >> Thanks Raul, I am familiar with these ideas, and using x: is almost a > reflex now. > >> > >> I feel that to protect the new J user, mod should convert to extended > precision automatically or issue an warning message. Giving tha answer zero > is very misleading. > >> > >> PS I am not so concerned with small numbers and measurability as with > large numbers and primality. Heisenberg's Uncertainty Principle is not > usually an issue for me :) > >> > >> Ragards, Rob. > >> > >>> On 7 Sep 2017, at 11:32, Raul Miller <rauldmil...@gmail.com> wrote: > >>> > >>> The answer, oddly enough, is: yes. > >>> > >>> The philosophical arguments are buried here: > >>> > >>> https://en.wikipedia.org/wiki/Accuracy_and_precision > >>> > >>> The technical issues are buried here: > >>> > >>> https://en.wikipedia.org/wiki/IEEE_754 > >>> > >>> That said, if you have reason to be using numbers which are precise > >>> beyond anyone's ability to measure (and keep in mind Heisenberg > >>> Uncertainty as one of the practical limits on measurability), you > >>> should probably be using extended precision numbers (123x instead of > >>> 123). This will give you exact results in exchange for a performance > >>> penalty. > >>> > >>> Thanks, > >>> > >>> -- > >>> Raul > >>> > >>> > >>>> On Thu, Sep 7, 2017 at 4:42 AM, Rob B <rb75...@me.com> wrote: > >>>> On reflection my real question is; should mod suddenly and without > warning give the wrong answer when a number gets suffiently large? I have > been caught by this many times. The incorrect answer zero is problematic as > it suggests divisibility. > >>>> > >>>> Apologies if this has all been discussed before. > >>>> > >>>> Regards, Rob Burns. > >>>> > >>>> > >>>> > >>>>> On 6 Sep 2017, at 09:11, Rob B <rb75...@icloud.com> wrote: > >>>>> > >>>>> Thanks, > >>>>> > >>>>> I now see it's reasonable for ^ to convert to flost and *: to remain > exact. > >>>>> > >>>>> The other discrepancy is probably due to my old version, iPad 701. > >>>>> > >>>>> Regards, Rob Burns. > >>>>> > >>>>>> On 5 Sep 2017, at 17:48, HenryRich <henryhr...@gmail.com> wrote: > >>>>>> > >>>>>> datatype 47^2 > >>>>>> > >>>>>> floating > >>>>>> > >>>>>> > >>>>>> So > >>>>>> > >>>>>> (n^2) | 5729082486784839 > >>>>>> > >>>>>> is promoted to float, and loses precision. Same when the big > number is extended - it's converted to float. > >>>>>> > >>>>>> For > >>>>>> > >>>>>> (x: n^2) | 5729082486784839 > >>>>>> > >>>>>> I get 147 as the result. > >>>>>> > >>>>>> Henry Rich > >>>>>> > >>>>>>> On 9/5/2017 12:41 PM, Rob B wrote: > >>>>>>> Could someone explain this please? > >>>>>>> > >>>>>>> n=.14 > >>>>>>> n > >>>>>>> 14 > >>>>>>> (*: n) | 5729082486784839 > >>>>>>> 147 > >>>>>>> 196 | 5729082486784839 > >>>>>>> 147 > >>>>>>> (n^2) | 5729082486784839 > >>>>>>> 0 > >>>>>>> (n^2) | 5729082486784839x > >>>>>>> 0 > >>>>>>> (x: n^2) | 5729082486784839 > >>>>>>> 0 > >>>>>>> (x: n^2) | 5729082486784839x > >>>>>>> 147 > >>>>>>> > >>>>>>> > >>>>>>> Regards, Rob Burns > >>>>>>> ------------------------------------------------------------ > ---------- > >>>>>>> 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 > >>> ---------------------------------------------------------------------- > >>> 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 > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
