Stack Overflow, tail recursion and CPS
Hi all, I get a stack overflow when I want to insert a huge, lazy list into a Map. I have changed the insertion algo to use foldl to make it tail-recursive but still get a stack overflow as the "insert" remains lazy. Could CPS be a solution in these cases? Günther
Hello Neil,
thanks, that did indeed work.
I guess I shot myself in the foot a bit here ...
Cause my real problem isn't actually with Map but with IxSet (from HAppS)
which to my knowledge does not have some sort of strict insert function.
Me trying to be really clever just used Map as a random example here
quietly hoping to get confirmation for "Yes, CPS is the anwer to force
evaluation here, keep digging in that direction boy", or a straight CPS
solution which I then would just translate to my problem.
Um ...
Didn't work, you were to clever, thanks a bunch Neil :)
Günther
Am 14.01.2009, 18:32 Uhr, schrieb Neil Mitchell
Hi
I have changed the insertion algo to use foldl to make it tail-recursive but still get a stack overflow as the "insert" remains lazy.
Try foldl' and insertWith' - that should work.
Thanks
Neil
-- Erstellt mit Operas revolutionärem E-Mail-Modul: http://www.opera.com/mail/
On Wed, 2009-01-14 at 19:19 +0100, Günther Schmidt wrote:
Hello Neil,
thanks, that did indeed work.
I guess I shot myself in the foot a bit here ...
Cause my real problem isn't actually with Map but with IxSet (from HAppS) which to my knowledge does not have some sort of strict insert function.
Does it by any chance have a Control.Parallel.Strategies.NFData instance? If it should happen to, then replacing (I didn't look up the type of insert!) foldl insert empty xn with foldl' ((result.result) (`using` rnf) insert) empty xn (where result is the Semantic Editor Combinator[1] result e f = e . f) would give you as much strictness as possible. Which might not be an improvement. jcc [1] This term was invented by Conal Elliot at http://conal.net/blog/posts/semantic-editor-combinators/. Semantic Editor Combinators are a clever technique for making point-less code readable.[2] [2] Does making point-free code readable miss the point of point-free style?
participants (3)
-
Günther Schmidt -
Jonathan Cast -
Neil Mitchell