this was with j802. Was not aware this was an area that was fixed recently.
----- Original Message ----- From: bill lam <[email protected]> To: [email protected] Sent: Saturday, March 19, 2016 10:50 PM Subject: Re: [Jprogramming] Tail recursion (bug hijack) What is the timestamp of your jqt.exe? The stack size of windows jqt.exe should had already increased since this February. Сб, 19 мар 2016, Pascal Jasmin написал(а): > to make a slightly off topic reply, this will crash J (win 64) (using the > definitions in replied post) > > > vr =: ($:@v0) > recursive2=: vr`[email protected] > > recursive i.20 > > I can accept that I am using $: wrong, but if vr is defined as what appears > to be equivalent: > > vr =: $:@v0 > > then recursive2 -: recursive (no crash) > > Is there a special meaning to the parenthesized version that could be done > intentionally in some contexts? > > > > > > ----- Original Message ----- > From: Louis de Forcrand <[email protected]> > To: [email protected] > Sent: Saturday, March 19, 2016 8:48 AM > Subject: [Jprogramming] Tail recursion > > Let t3 be a recursive verb equivalent to >:@(3&{.) : > > t3=: $:@}:`>:@.(3 = #) > (>:@(3&{.) -: t3) i.1e3 > 1 > (>:@(3&{.) -: t3) i.1e4 > |stack error: t3 > | (>:@(3&{.)-:t3)i.10000 > T3=: >:@(}:^:(-.@(3 = #))^:_) > (>:@(3&{.) -: T3) i.1e3 > 1 > (>:@(3&{.) -: T3) i.1e4 > 1 > > Most of the time (and this is the point of this post), > > $:@v0`[email protected] <—> v1@(v0^:(-.@v2)^:_) > > The one possible exception is if v1 returns 1 BUT v0 is equivalent > to ] (for that particular iteration). Then the version using ^: stops, > while the recursive version doesn't. However, the problem with the > recursive version is the stack of course. This problem could be > fixed if special code existed to convert the recursive version to > an internal loop. I believe most Scheme interpreters are required > to do this, and it's called tail recursion. > > In the meantime, is there a better way to write this type of verb > (tacitly)? Say, for example, that I'm trying to successively remove > divisors of each number in a list (except the number itself), > removing them in a random order. In the end I should be left with > all the numbers which have no multiples of themselves in the list > (right?). Problems arise however if the number in question is prime; > the list won't be modified that iteration, and so the ^: version would > stop there. Is there another (relatively simple) way to do this tacitly? > For example: > > divisors=: (] #~ 0 = |~) >:@i. > v0=: -. }:@divisors@({~ ?@#) > v1=: ] > v2=: -.@(+./)@e. ;@:(<@}:@divisors"0) > recursive=: $:@v0`[email protected] > power=: v1@(v0^:(-.@v2)^:_) > recursive i.20 > 0 10 11 12 13 14 15 16 17 18 19 > power i.20 > 0 4 5 6 8 9 10 11 12 13 14 15 16 17 18 19 > > Obviously power stops prematurely. > Note that this is an extremely inefficient way to do this and is > only for demonstration purposes. > > Thanks, > Louis > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm -- regards, ==================================================== GPG key 1024D/4434BAB3 2008-08-24 gpg --keyserver subkeys.pgp.net --recv-keys 4434BAB3 gpg --keyserver subkeys.pgp.net --armor --export 4434BAB3 ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
