I would sooner get the right answer slowly than the wrong answer quickly. Regards, Rob.
> On 7 Sep 2017, at 13:48, Raul Miller <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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
