Ok, thanks!
Anton Wallgren On 26 May 2020, 10:43 +0200, 'Rob Hodgkinson' via Programming <[email protected]>, wrote: > It was a later enhancement to forks, see this reference: > https://code.jsoftware.com/wiki/Vocabulary/fork > <https://code.jsoftware.com/wiki/Vocabulary/fork> > > Basically it was felt that the strict 3 verb sequence (v1 v2 v3) called a > fork (which is function composition) could be more useful if it allowed a > leading noun as (n v2 v3). > > Rob > > > On 26 May 2020, at 6:36 pm, Anton Wallgren <[email protected]> wrote: > > > > 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 > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
