You could try something like this: m=. +:`] NB. Double, return same (m@.(100&<))^:_ ] 1 NB. Double until 100<result 128 (m@.(100&<))^:_ ] 10 160
"^:_" halts when the result remains the same. On Tue, May 26, 2020 at 7:54 PM ethiejiesa via Programming < [email protected]> wrote: > Oh cool. A Tabu search. Depending on your specific use case, you might be > able > to use 9!:33 to simply set an execution time limit. > > Anton Wallgren <[email protected]> wrote: > > 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 > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA Quantitative Consultant ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
