This will be fun to have. I don't "think" in expressions that are this long but I hope to get it glued together and try it.
You made this comment about me: (as I noticed you like 13 : n so much for mechanically converting explicit to tacit) I really don't care as much about the tacit result as I do about having a record of where the arguments belong in the expression. This explicit form is most instructive to me at this stage. It is a good way to begin to capture your ideas and generate code that extends the use of your expressions. As I read and write more J I may or may not begin to "think" in tacit expressions. Or the idiomatic versions with lots of idioms using @ may become easier. Linda -----Original Message----- From: programming-boun...@jsoftware.com [mailto:programming-boun...@jsoftware.com] On Beh alf Of Dan Bron Sent: Friday, February 10, 2012 6:53 PM To: 'Programming forum' Subject: Re: [Jprogramming] Another early morning exercise Linda wrote: > I was trying to find a situation where you have to > use @ instead ( of [: ). I think Raul pointed out that u@v <=> ([: u v)"v so that you never /have/ to use @ . You can mechanically convert from one formulation to the other. So I figured I'd provide you a tool to do just that (as I noticed you like 13 : n so much for mechanically converting explicit to tacit). The adverb Cap, defined below, takes a verb argument, and derives a verb identical in function, but removes all mentions of @ , and substitutes [: for glue. Well, the derived verb is not identical in all situations; in particular, instead of imposing the u@v <=> ([: u v)"v rule universally, I tried to simplify this to [: u v where possible, to reduce the noise factor (at the cost of a result which is not identical under all situations, just the most common uses). The adverb is all one line (fully fixed functional form!) but to get it safely through email I've line-wrapped it. ". noun define -. CRLF Cap_z_ =: ((<":0)`) (<`) ((<@((3 (":@:[ <@,&< ]) [:`'' , ]) (<@(({.;:'"') (,<) ,&{:~) {::~ ('';1;0) }.~ _2 * 0 {:: [)~ (0 +./ .>~^:] _1 |. 1:`'' , ([: |.&.>&.> (;:'@[b.') <@((,<)/)@:," 1 0 ])) ; {:)^:(2=#)@:>@:{:^:((({.;:'@')={.) *. (2=#))@:($:&.> )^:(0 < L.))`) (@.(0;1;2 3)) (`:6) ) Examples: f@g Cap [: f g f@g@h Cap [: ([: f g) h f@(g@h) Cap [: f [: g h (+/ +: % #) Cap +/ (+: % #) (+/ +:@% #) Cap +/ ([: +: %) # {.@$ Cap [: {. $ {.@+. Cap ([: {. +.)"0 0 0 <@%. Cap ([: < %.)"2 _ 2 %.@< Cap ([: %. <)"_ 0 0 But if you take the bait, watch for the hook: I wrote this tool which "avoids @", so that we don't need to have any more discussions about how to do that, challenges which impose it as a constraint, or extended threads regarding the right-to-leftness of composition in J. Deal? -Dan PS: Note that due to a bug in 5!:5, typing Cap in the IJX window results in a domain error. So, for those who wish to peek behind the veil, the source material is here: http://www.jsoftware.com/svn/DanBron/trunk/environment/at2cap.ijs . Adverbial programmers might find a tool or two worth adding to their kits. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
