[Jprogramming] Puzzling result

[Rob B]

I would sooner get the right answer slowly than the wrong answer quickly.

Regards, Rob.

> On 7 Sep 2017, at 13:48, Raul Miller <rauldmiller at 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 <rb75app at 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 <rauldmiller at 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 <rb75app at 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 <rb75app at 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 <henryhrich at 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
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