I am trying to understand what f does. ]a=:?>:i.6 0 1 0 1 0 4 ]a=:=a 1 0 1 0 1 0 0 1 0 1 0 0 0 0 0 0 0 1 ]b=:?>:i.6 0 0 2 3 2 3 f=: 13 :'x #@# y' a f b 3 2 1 f #@# Raul's solution works. However, I still can't figure out what has happened to get the result that both provide.
NB. ([: u v)"v j=: 13 :' x([:##)"# y' a j b 3 2 1 j ([: # #)"_ 1 _ Usually if I write an explicit definition without @ I can figure out how the result was obtained. Both f and j have not yet made sense to me. Linda -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Peter B. Kessler Sent: Wednesday, January 02, 2013 2:43 PM To: [email protected] Subject: Re: [Jprogramming] atop continues to puzzle me Am I correct that in your example, you are using Open (>) just for its rank (monadic 0), and not for its verb (the inverse of Box)? That is < @ i. @ ]"0 ( 2 3 4 ) +---+-----+-------+ |0 1|0 1 2|0 1 2 3| +---+-----+-------+ would work as well. (Parens around the argument are needed to separate it from the Rank conjunction ("0). I've also seen Same (]) used as a separator.) I think the point is that you want the Box Atop Integers (< @ i.) to operate on the atoms of its argument, not on the argument as a whole. A more explicit way of saying you want a rank 0 verb is to use (< @ i.)"0 ( 2 3 4 ) +---+-----+-------+ |0 1|0 1 2|0 1 2 3| +---+-----+-------+ I find it confusing when I see Open used just for its rank. (But I'm learning. :-) If my explanation is correct, maybe it will help someone else learn this idiom. ... peter Raul Miller wrote: > Here's a definition for at which works exactly like @ > > at=: 2 :'([: u v)"v > > For example:' > <at i. at > 2 3 4 > > Now, looking at that, you may think that this means that [: is somehow > superior to @ but note that [: is not necessary > > at=: 2 :'u@:v"v' > > Note that in J, @: and @ (without the colon) are different words. > > It's also possible to replace @: with an explicit definition, but > that's probably best left for another time. > > FYI, > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
