Thanks for pointing this out. I've had always taken this for granted and pointing it out actually made me understood the behavior/speed of some of my code.
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Marshall Lochbaum Sent: Monday, August 30, 2010 10:36 AM To: 'Programming forum' Subject: Re: [Jprogramming] Splitting an integer into its digits The limiting factor here isn't the speed of the part that removes the initial 0s, it's the fact that you are doing the whole thing rank 1. This way, (+/"1@({&f)) has to reinitialize for every row, which is SLOW. Essentially, this approach is the same as (stuff)@digits"0 in that the output from digits for each scalar is rank 1, so then applying a rank 1 verb to it is the same but with more overhead. The only way to really get rid of the padding problem is to do it for only the numbers which have a certain number of digits, and loop over all the digits less than your maximum. Marshall -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of gary ng Sent: Sunday, August 29, 2010 9:26 PM To: Programming forum Subject: Re: [Jprogramming] Splitting an integer into its digits On Sun, Aug 29, 2010 at 5:36 PM, Marshall Lochbaum <[email protected]> wrote: > Oh, or > }.~ [: i.&1 ~:&0 > That should be really fast. > Not sure if I am doing the right thing or there is something else(I am a newbie in J): 6!:2 ' +/"1@({&f)@(}.~ [: i.&1 ~:&0)"1@(digits)i.1000000' 2.90104 6!:2 ' +/"1@({&f)@(#~[:>&0+/\)"1(digits)i.1000000' 2.75834 | 6!:2 ' +/"1@({&f)@(#~[:+./\~:&0)"1@(digits)i.1000000' 2.85498 ---------------------------------------------------------------------- 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
