I guess I learned APL when you essentially applied verbs from right to left. When you use extensive use of @ you seem to loose some of the beauty of the simplicity of understanding.
-----Original Message----- From: programming-boun...@jsoftware.com [mailto:programming-boun...@jsoftware.com] On Behalf Of Marshall Lochbaum Sent: Wednesday, October 26, 2011 11:14 PM To: Programming forum Subject: Re: [Jprogramming] problem with under You can use &.: and simply make the verb rank 0 (which is the rank of >), and then expand that to an expression using @: . However, &.> is an idiom that is really useful (it's the analogue of "_1 for arrays of boxes), so your code will be shorter and clearer if you learn to use it. I =: ([:/:":) &.> I =: ([:/:":) &.:> "0 I =: < @: ([:/:":) @: > "0 These give some equivalent forms for &.> , using adverb trains: &.> (&.:>) ("0) (<@:) (@:>) "0 One helpful way to think about it is to consider arrays of boxes, where &.> simply does the verb inside each box: <"0 i.10 --T-T-T-T-T-T-T-T-T-┐ │0│1│2│3│4│5│6│7│8│9│ L-+-+-+-+-+-+-+-+-+-- >: &.> <"0 i.10 --T-T-T-T-T-T-T-T-T--┐ │1│2│3│4│5│6│7│8│9│10│ L-+-+-+-+-+-+-+-+-+--- Now when the argument is not boxed, open does nothing, but it has rank zero, so it still only works on atoms. Thus one way to think of it is that each atom of the argument is in its own virtual box before application, and then evaluation goes as show above. Marshall 2011/10/26 Linda Alvord <lindaalv...@verizon.net> > Somehow I didn't make my purpose very clear. I was trying to get a simple > expression for l that didn't use &. And thought it should be possible > from the definition in the dictionary. Can anyone provide a tacit > definition without &. Thanks. Linda > > > u&.v is u&.:v"({. v b. 0) > > a=: 10123 > b=: 32110 > l=:([:/: ":)&.> > l a, > ----------T---------┐ > │1 0 2 3 4│4 2 3 1 0│ > L---------+---------- > > m=:([:/:":)&.:>"({.> b. 0) > m > ([: /: ": )&.:>"({.> b, 0) > > m a,b > ----------T---------┐ > │1 0 2 3 4│4 2 3 1 0│ > L---------+---------- > > -----Original Message----- > From: programming-boun...@jsoftware.com > [mailto:programming-boun...@jsoftware.com] On Behalf Of Henry Rich > Sent: Wednesday, October 26, 2011 9:28 PM > To: Programming forum > Subject: Re: [Jprogramming] problem with under > > Different people have different standards of acceptable rigor, I reckon. > To me, the context isn't enough to overcome the inaccuracy of the > statement. > > FWIW, in my first post on this I had originally typed 'wrong' and > replaced it with 'misleading', following much the train of thought you > have offered. I still think Ye Dic is wrong; but I'm dead certain it is > misleading. > > I think the current language is a holdover from the days before &.: . > Now I can say that > > u&.v is u&.:v"({. v b. 0) > > but back then there was no notation for that idea, and the Dictionary > just came close and was content. I think readers deserve better now. > > Henry Rich > > On 10/26/2011 9:09 PM, Raul Miller wrote: > > On Wed, Oct 26, 2011 at 5:52 PM, Henry Rich<henryhr...@nc.rr.com> > wrote: > >> I think it's fair to say the Dictionary is misleading because > >> > >> a. it contains a line that is not true; > > > > It's only "not true" when taken out of context -- you have to (a) > > ignore preceding material, and then (b) generalize a remaining > > statement and believe it covers the case treated by that preceding > > material > > > > This is somewhat like saying that a dictionary is wrong for claiming > > that "light" means "not weighing much" because someone who was not a > > native speaker was confused because they needed to treat a context > > having to do with illumination. > > > > It's only wrong if you overgeneralize. > > > ---------------------------------------------------------------------- > 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
