does counting suffice? then that would be φ which I’m sure
someone must have written code for already
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
