I'm not sure "acceptable" is nuanced enough - it's definitely an issue worth understanding.
That said, mathematics routinely deals with infinities and computers are always finite. This creates inevitable tensions and design tradeoffs, regardless of the context. However, in some contexts those tradeoffs will be near ideal, in other contexts, those tradeoffs will be uncomfortable, and in yet other contexts they might be showstoppers. Here, in this context, J's tradeoffs are slightly uncomfortable, but manageable. But the reasons why have to do with the nature of the measurements which produce numbers. I hope this makes sense... Thanks, -- Raul On Thu, Sep 7, 2017 at 2:19 PM, Rob B <rb75...@me.com> wrote: > Since the consensus seems to be that this is acceptable, I will say no more. > > Thanks for taking the time to reply. > > Regards, Rob. > >> On 7 Sep 2017, at 19:05, Raul Miller <rauldmil...@gmail.com> wrote: >> >> Where would a new user get those large numbers? >> >> That said, new users should be expected to either (a) read the >> documentation, or (b) be puzzled at times and perhaps have to talk >> with people. >> >> In this case, http://www.jsoftware.com/help/dictionary/dcons.htm might >> be relevant. >> >> Thanks, >> >> -- >> Raul >> >>> On Thu, Sep 7, 2017 at 9:41 AM, Rob B <rb75...@me.com> wrote: >>> How would a new user know that using mod with large numbers was 'asking the >>> wrong question'? >>> >>> Surely user-friendly code protects the user as its first priority? >>> >>> Regards, Rob. >>> >>>> On 7 Sep 2017, at 14:24, Eric Iverson <eric.b.iver...@gmail.com> wrote: >>>> >>>> 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 >>> ---------------------------------------------------------------------- >>> 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
