To find a reference for David's explanation, see section II F. Trains in the Dictionary -- go to
http://www.jsoftware.com/docs/help701/index.htm and click on Dic then click on F. Trains in the right column. On 10/29/2011 4:18 AM, David Vaughan wrote: > (+/ *:) 3 4 > Is > 3 4 +/ *: 3 4 > Is > 3 4 +/ 9 16 > > ([: +/ *:) 3 4 > Is > +/ *: 3 4 > Is > +/ 9 16 > > ___________________________ > > David Vaughan > > On 29 Oct 2011, at 08:09, "Linda Alvord"<[email protected]> wrote: > >> Remove either atop @ or at @: and you get: >> >> (+/ *:) 3 4 >> 12 19 >> 13 20 >> >> but when you put in cap [: you get the result of @: rather than @ >> >> ([:+/ *:) 3 4 >> >> 25 >> >> Linda >> >> -----Original Message----- >> From: [email protected] >> [mailto:[email protected]] On Behalf Of Kip Murray >> Sent: Thursday, October 27, 2011 4:03 PM >> To: Programming forum >> Subject: Re: [Jprogramming] problem with under >> >> I like especially your second form I =: ([:< [: /: ":)"0 >> >> For the third form I =:< @ /: @ ": " 0 note that [: f g and f @: g are >> always equivalent, but f @: g and f @ g are not when g has rank 0 -- >> conjunction @: always uses sequential processing, but conjunction @ uses >> parallel processing when g has rank 0, as shown below. >> >> >> (+/ @: *:) 3 4 >> 25 >> >> (+/ @ *:) 3 4 >> 9 16 >> >> >> In the first case above the right to left flow chart is >> >> 25<-- +/<-- 9 16<-- *:<-- 3 4 (sequential processing) >> >> while in the case involving @ the flow chart is >> >> <-- 9<-- *:<-- 3 >> 9 16<-- +/ (parallel processing because *: is rank 0) >> <-- 16<-- *:<-- 4 >> >> >> As I nearly always want sequential processing I use >> >> [: f [: g h (read "the f the g h") >> >> or >> >> f @: g @: h (read math's "f o g o h") >> >> >> Check: >> >> ([: +/ *:) 3 4 >> 25 >> >> >> On 10/27/2011 5:21 AM, Raul Miller wrote: >>> Also, for the domain in question, we are not using> for anything but its >> rank. >>> >>> Thus we could simplify: >>> >>> I =: ([:< [: /: [: ": ])"0 >>> >>> Also, since we are always using this as a monad, we could further >> simplify: >>> >>> >>> I =: ([:< [: /: ":)"0 >>> >>> Though, personally, I find myself comfortable using @ >>> >>> I =:<@/:@":"0 >>> >>> Or, going back to the original message, and applying @ to achieve what >>> the dictionary was talking about: >>> >>> <@([: /: ":)@>a,b >>> >>> Or, using "0 to replace @> >>> >>> <@([: /: ":)"0 a,b >>> >>> But if you are using trains in boxes, maybe it's better to state that >>> explicitly, and that could also get rid of any of the @ conjunctions: >>> >>> ([: /: ":) L:0<"0 a,b >>> >>> That said, when you replace a shorter expression with a longer one, I >>> think you should expect the longer one to lose some of the grace of >>> the original. >>> >>> I hope this helps. >>> >> ---------------------------------------------------------------------- >> 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 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
