[Jprogramming] Bug? Re: Factoring

[Henry Rich]

The bug seems to be confined to the argument 1x .  4 p: x searches x+2, 
x+4, ... for primes.  It starts at x+1 if x is even or is non-extended 
1; but for extended 1 it starts at x+2.

Henry Rich

On 4/25/2020 4:48 AM, 'Michael Day' via Programming wrote:
> Investigating how to factor quite large numbers in J,  I've just 
> bumped into this curiosity, which
>
> wrecked my loopy experiment at an early stage!...
>
>    4 p: 1
> 2
>    4 p: 1x   NB. need to try extended in some cases...
> 3
>
> !
>
> Thanks for any advice,
>
> Mike
>
>
> On 25/04/2020 00:15, 'Mike Day' via Programming wrote:
>> Numbers of divisors below, not the divisors themselves... the thread 
>> had split! I was attempting to comment on Hauke Rehr’s post.
>> M
>>
>> Sent from my iPad
>>
>>> On 24 Apr 2020, at 23:52, 'Jon' via Programming 
>>> <programming at jsoftware.com> wrote:
>>>
>>> This is missing a few divisors. It seems Skip's original method 
>>> would be difficult to beat. It's O(n) in time and space. You could 
>>> improve space complexity by doing a simple loop, but as far as I can 
>>> see there are no shortcuts, and the best way is to just "brute 
>>> force" it.
>>>
>>> ⁣Sent from BlueMail ​
>>>
>>>> On Apr 25, 2020, 5:35 AM, at 5:35 AM, 'Mike Day' via Programming 
>>>> <programming at jsoftware.com> wrote:
>>>> I think this is near to the approved way:
>>>>
>>>>   (*/"1@:>:@(_& q:))24 360 4711
>>>> 8 24 4
>>>>
>>>> Mike
>>>>
>>>> Sent from my iPad
>>
>


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