I agree, Don. I really was using a post from Roger because I find his the most difficult to untangle. This thread was a good one to explain my new thoughts about @ and [:
My challenges are topics I might use to teach high school seniors studying precalculus, probability and statistics. They are similar to old APL contests I invented while I was teaching APL - to get better with the language myself. However, I'm not sure what would work in classes these days. At least I'm having fun with the readers of the forum. J is even becoming fun to use! Linda -----Original Message----- From: programming-boun...@jsoftware.com [mailto:programming-boun...@jsoftware.com] On Behalf Of Don Guinn Sent: Friday, February 03, 2012 12:04 AM To: Programming forum Subject: Re: [Jprogramming] Understanding C. , A. Might want to get beginners a little comfortable with J before showing them C. and A. On Thu, Feb 2, 2012 at 7:56 PM, Linda Alvord <lindaalv...@verizon.net>wrote: > I am rethinking my concern with @ and [: and am leaning toward using > explicit definitions as a way of teaching J to beginners as a natural > mathematical language. > > Some of the programmers responding to the forum think in idioms and use @ > happily. > > f > <:@-@[ C.&.|. ] > i > -@#@[ |. C. > k > <@i.@-@>:@[ C. ] > > 0thers favor the tacit approach with lots of [: > > g > ] C.&.|.~ [: <: [: - [ > h > [: |. ([: <: [: - [) C. [: |. ] > j > C. |.~ [: - [: # [ > > > Both styles are appropriate and I should not suggest one way or the other. > Many of you have suggested this. > > > We are looking for a simple way to introduce J to beginners. In my > opinion > we would introduce J as a mathematical language for solving problem. > > > I am suggest starting with expressions that produce desired results. > Developing from right to left may come naturally. > > (<:-3 6)C.&.|.'abc*ef*g' > **abcefg > > The next step is making explicit functions indicating if the intended use > is > monadic or dyadic. There is no use of @ or [: allowed at this point. > > g=: 13 :'(<:-x)C.&.|.y' > h=: 13 :'|.(<:-x)C.|.y' > j=: 13 :'(-#x)|.x C.y' > > Now exploring the tacit definitions would be appropriate in some > environments and can be explored an studied in terms of forks and hooks. > At this special code and common idioms can be explored and timing of > expressions can be compared. In the end all roads lead to Rome. > > 3 6 f 'abc*ef*g' > **abcefg > 3 6 g 'abc*ef*g' > **abcefg > 3 6 h 'abc*ef*g't > **abcefg > 3 6 i 'abc*ef*g' > **abcefg > 3 6 j 'abc*ef*g' > **abcefg > > > -----Original Message----- > From: programming-boun...@jsoftware.com > [mailto:programming-boun...@jsoftware.com] On Behalf Of Linda Alvord > Sent: Wednesday, February 01, 2012 6:01 PM > To: 'Programming forum' > Subject: Re: [Jprogramming] Understanding C. , A. > > Sorry I missed the version by Arie. Nice! > > 3 6 (i=:-@#@[ |. C.) 'abc*ef*g' > **abcefg > i > -@#@[ |. C. > > j=: 13 :'(-#x)|.x C.y' > j > C. |.~ [: - [: # [ > > 3 6 j 'abc*ef*g' > **abcefg > > Please let me know if you have concerns or modifications as I plan to use > different rules beginning with challenge 6. > > Henceforth I'll have no opinion concerning the merits of @ and [: I > hope > to learn to favor them both gracefully. > > Linda > > -----Original Message----- > From: programming-boun...@jsoftware.com > [mailto:programming-boun...@jsoftware.com] On Behalf Of Linda Alvord > Sent: Wednesday, February 01, 2012 5:20 PM > To: 'Programming forum' > Subject: Re: [Jprogramming] Understanding C. , A. > > I'm happiest with the explicit version. It shows the arguments needed for > the application. > > 3 6 (f=:<:@-@[ C.&.|. ]) 'abc*ef*g' > **abcefg > 3 6 f a=:'abc*ef*g' > **abcefg > > g=: 13 :'(<:-x)C.&.|.y'! > 3 6 g a > **abcefg > > f > <:@-@[ C.&.|. ] > g > ] C.&.|.~ [: <: [: - [ > g=: 13 :'(<:-x)C.&.|.y' > > J provides the ~ which shows up in the tacit version above. > > Then there is h with no ~ and no &. > > h=: 13 :'|.(<:-x)C.|.y' > h > [: |. ([: <: [: - [) C. [: |. ] > 3 6 h a > **abcefg > > Linda > > > -----Original Message----- > From: programming-boun...@jsoftware.com > [mailto:programming-boun...@jsoftware.com] On Behalf Of Roger Hui > Sent: Wednesday, February 01, 2012 11:26 AM > To: Programming forum > Subject: Re: [Jprogramming] Understanding C. , A. > > Personally, I dislike expressions with multiple uses of ~ as they make my > head spin. > > 3 6 (C.&.|.~ <:@-)~ 'abc*ef*g' > **abcefg > 3 6 (<:@-@[ C.&.|. ]) 'abc*ef*g' > **abcefg > > I much prefer the second over the first. > > > > On Wed, Feb 1, 2012 at 8:05 AM, Aai <agroeneveld...@gmail.com> wrote: > > > Ah, I see that's a bit like yours David. > > > > Modifying it for 1< #x > > > > 3 6 (C. |.~ -@#@[) 'abc*ef*g' > > **abcefg > > > > > > (from Essays) > > > > 3 6 (C.&.|.~ <:@-)~ 'abc*ef*g' > > **abcefg > >k > > > > > > > > On 01-02-12 16:47, Aai wrote: > > > Sorry for the noise. You should forget the previous ones I sent: they > > > are wrong. > > > > > > It looks like this one is ok: > > > > > > mtf=:_1&|.@C. > > > > > > ]samples=: '*abcef' |."0 1 ~-i.6 > > > *abcef > > > f*abce > > > ef*abc > > > cef*ab > > > bcef*a > > > abcef* > > > > > > > > > ]res=: '*' ([,-.~) "1 samples > > > *abcef > > > *fabce > > > *efabc > > > *cefab > > > *bcefa > > > *abcef > > > > > > res -: mtf&>/"1 (;~I.@:('*'&=))"1 samples > > > 1 > > > > > > > > > > > > > > > > -- > > Met vriendelijke groet, > > @@i = Arie Groeneveld > > > > ---------------------------------------------------------------------- > > 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 > > ---------------------------------------------------------------------- > 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
