Hi, thank you, missed this mail! You are of course right, more details is better :)
I think that posting complete code for this question might obscure the idea, as its more about a pattern I want to use occasionally. An example would be for a Tabu search algorithm I might know a lower bound for the objective function, so if I during search find a solution whose objective value equals the lower bound, I do not want to continue as I know that I can’t find a better solution. If the lower bound is not tight however, or I do not manage to find such a solution, I wish to abort the search after some set number of iterations, as the search could go on forever. Regards, Anton Wallgren On 26 May 2020, 10:39 +0200, ethiejiesa via Programming <[email protected]>, wrote: > Hey Anton, > > Welcome to the J-verse! > > FWIW, the question as stated makes me suspect that you're (unconsciously) > trying to fit J into an imperative programming paradigm. I would venture that > you'd get better answers by more directly sharing what you're trying to > accomplish and the problems thus encountered. > > One simple formula is to simply share the input you have and output you want. > From lurking here on the forums for a bit, those kinds of questions often get > a > lot of good attention. It's often the case that one of the old guard peeps in > with a short and sweet solution that is both beautiful and humbling. > > Cheers, > > > Anton Wallgren <[email protected]> wrote: > > Hi, thanks! But as Raul pointed out, this does not allow me to specify max > > iterations. > > > > Regards, Anton Wallgren > > On 26 May 2020, 08:39 +0200, '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
