I think this is near to the approved way: (*/"1@:>:@(_& q:))24 360 4711 8 24 4
Mike Sent from my iPad > On 24 Apr 2020, at 21:13, Hauke Rehr <[email protected]> wrote: > > I now have an answer for the number of results: > > */ >: +/"1 (=/~ ~.) q: 4711 > 4 > */ >: +/"1 (=/~ ~.) q: 42 > 8 > > I hesitate using =/~ (it’s actually deprecated) > but I wouldn’t know a better way in this case > > >> Am 24.04.20 um 21:09 schrieb Skip Cave: >> I have used the wrong terminology. I want to find all the positive integer >> *divisors* of an integer n (not just primes) which includes 1 and the >> integer. >> Here's a brute force verb I wrote: >> div=:3 : 'a#~0=(a=.1+i.y)|y' >> Test it: >> div each 40+i.5 >> │1 2 4 5 8 10 20 40│1 41│1 2 3 6 7 14 21 42│1 43│1 2 4 11 22 44│ >> However my div verb is inefficient, slow, and runs out of memory quickly on >> larger integers. Is there a way to take advantage of J's prime factoring >> verb q: to more efficiently find and/or count *all* positive divisors (not >> just primes) of a large (>1e7) integers? >> Skip >> Skip Cave >> Cave Consulting LLC >> Skip Cave >> Cave Consulting LLC >>> On Fri, Apr 24, 2020 at 1:31 PM Roger Hui <[email protected]> wrote: >>> See https://code.jsoftware.com/wiki/Essays/Factorings >>> >>> >>> >>> On Fri, Apr 24, 2020 at 11:29 AM Skip Cave <[email protected]> >>> wrote: >>> >>>> I want to find all the integer factors of a positive integer, >>>> which includes 1 and the integer. >>>> Here's a brute force verb I wrote: >>>> fac=:3 : 'a#~0=(a=.1+i.y)|y' >>>> >>>> Test it: >>>> >>>> fac each 40+i.5 >>>> >>>> │1 2 4 5 8 10 20 40│1 41│1 2 3 6 7 14 21 42│1 43│1 2 4 11 22 44│ >>>> >>>> >>>> However my fac verb is inefficient, slow, and runs out of memory quickly >>> on >>>> larger integers. Is there a way to take advantage of J's prime factoring >>>> verb q: to more efficiently find and/or count *all* positive factors (not >>>> just primes) of a large (>1e7) integers? >>>> >>>> >>>> Skip >>>> >>>> >>>> Skip Cave >>>> Cave Consulting LLC >>>> ---------------------------------------------------------------------- >>>> 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 > > -- > ---------------------- > mail written using NEO > neo-layout.org > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
