Oh, cool! Why does this work? I would have assumed that I needed to write (10”_ > ]) to achieve the constant function 10.
Thanks, Anton Wallgren On 26 May 2020, 10:27 +0200, 'Rob Hodgkinson' via Programming <[email protected]>, wrote: > Note that for the v function you don’t need to use @, but just a simple train > of 3 verbs (100 > ]) … consider the 100 a constant function returning 100. > > (2&*)^:(10 > ])^:3 ] 1 > 8 > (2&*)^:(10 > ])^:5 ] 1 > 16 > > > > On 26 May 2020, at 6:02 pm, Anton Wallgren <[email protected]> wrote: > > > > Yes, maybe for loop is the way to go. It just seems very un-J :). I did try > > f^:v^:n earlier, but it didn’t work, it ran f 2*n times. But when I try it > > now with my simple example, > > > > (2&*)^:(10&> @ ])^:3 ] 1 > > > > returns 8, and > > > > (2&*)^:(10&> @ ])^:5 ] 1 > > > > returns 16, as expected. Maybe there is something going on with my “v” in > > my earlier code. > > > > Thanks, Anton Wallgren > > On 26 May 2020, 09:11 +0200, Raul Miller <[email protected]>, wrote: > > > ^:_ doesn't impose the max limit on iterations, though... > > > > > > I think, for something that quirky, I'd just use a for loop. That > > > said, f^:v^:n would work -- I'm just not sure it's optimized > > > adequately. > > > > > > I hope this helps, > > > > > > -- > > > Raul > > > > > > On Tue, May 26, 2020 at 2:39 AM 'Rob Hodgkinson' via Programming > > > <[email protected]> wrote: > > > > > > > > Hi Anton, welcome to J. > > > > > > > > This is a further parameter to the power operator (^:) described here: > > > > > > > > https://code.jsoftware.com/wiki/Vocabulary/Loopless > > > > <https://code.jsoftware.com/wiki/Vocabulary/Loopless> Section “Types of > > > > Loops” and the row in the table “Apply a verb repeatedly”, “Until a > > > > condition is met”. > > > > Use Power ([x] u^:v^:_ y) > > > > > > > > For your example, double while a condition (eg let’s say while the > > > > sequence is < 100 and stop with the value that breaches that condition > > > > …) > > > > > > > > 2&* ^:(100>])^:_ (1) NB. Sequence here is 1,2,4,8,16,32,64,128 > > > > 128 > > > > > > > > 2&* ^:(100>])^:_ (5) NB. Sequence is 5, 10, 20, 40, 80, 160 > > > > 160 > > > > > > > > Best, Rob > > > > > > > > > On 26 May 2020, at 4:09 pm, Anton Wallgren <[email protected]> > > > > > wrote: > > > > > > > > > > Hello! > > > > > > > > > > Fairly recent J enthusiast here. I’m wondering about the idiomatic > > > > > way to iterate at most n times? I.e. do f^:n y, but with the > > > > > possibility of an early exit if some condition is met. Is it (u F. ]) > > > > > y, where u is f but with some Z:’s added? E.g > > > > > > > > > > f=: 2&* > > > > > MAX=: n > > > > > > > > > > u=: monad define > > > > > _2 Z: -.*MAX=: MAX - 1 > > > > > _2 Z: some other condition > > > > > f y > > > > > ) > > > > > > > > > > But then you need to globally assign and reassign MAX and this > > > > > doesn’t feel very elegant. Another option of course is to use a > > > > > for-loop with break. > > > > > > > > > > Thanks, Anton Wallgren > > > > > ---------------------------------------------------------------------- > > > > > 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
