>From http://www.jsoftware.com/jwiki/Essays/Divisors
div=: /:~ @: , @: > @: (*/&.>/) @: ((^ i.@>:)&.>/) @: (__&q:) div 360 1 2 3 4 5 6 8 9 10 12 15 18 20 24 30 36 40 45 60 72 90 120 180 360 On Tue, Jun 10, 2014 at 10:10 AM, Jon Hough <[email protected]> wrote: > My attempt at making a verb that finds the total of all proper divisors of > an integer seems to work. > e.g. if n = 12, the sum of proper divisors is 1 +2 +3+4+6 = 16 (note 12 is > not included) > This verb is actually equal to the "sigma function" minus n.Wikipedia > explanation: http://en.wikipedia.org/wiki/Divisor_function > (I essentially used the equation for sigma_x(n) where x = 1) > my verb: > > sum =.(((*/@:-&1@:{.)%~(*/@:-&1@:({.^(1&+@:,@:}.))))@:(2&p:))-] > This seems ok, but is not aesthetically pleasing, and seems to be very > bracketty, and given that the mathematical equation is pretty concise I am > surprised the J verb is so long. If anyone knows a nicer way of doing this > I would be grateful to see it. > Regards. > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
