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
