Thank you very much! That solved it ;)I had to put explicit type signature in front of advance in order to compile From: cgaebel@uwaterloo.ca Date: Wed, 28 Nov 2012 08:01:38 -0500 Subject: Re: [Haskell-cafe] How to incrementally update list To: edwards.benj@gmail.com CC: bmaxa@hotmail.com; haskell-cafe@haskell.org Here's a version that works: import Control.DeepSeq list = [1,2,3,4,5] advance l = force $ map (\x -> x+1) l run 0 s = srun n s = run (n-1) $ advance s main = do let s = run 50000000 list putStrLn $ show s The problem is that you build of a huge chain of updates to the list. If we just "commit" each update as it happens, we'll use a constant amount of memory. Haskell's laziness is tricky to understand coming from imperative languages, but once you figure out its evaluation rules, you'll begin to see the elegance. Ηope this helps, - Clark On Wed, Nov 28, 2012 at 7:07 AM, Benjamin Edwards wrote: TCO + strictnesses annotations should take care of your problem. On 28 Nov 2012 11:44, "Branimir Maksimovic" wrote: Problem is following short program:list = [1,2,3,4,5] advance l = map (\x -> x+1) l run 0 s = srun n s = run (n-1) $ advance s main = do let s = run 50000000 list putStrLn $ show s I want to incrementally update list lot of times, but don't knowhow to do this. Since Haskell does not have loops I have to use recursion,but problem is that recursive calls keep previous/state parameterleading to excessive stack.and memory usage.I don't know how to tell Haskell not to keep previous state rather to release so memory consumption becomesmanagable. Is there some solution to this problem as I think it is rathercommon? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

On Sat, Dec 1, 2012 at 1:16 AM, Mark Thom wrote:

...

Is there a paper or other single resource that will help me thoroughly understand non-strictness in Haskell?

If performance is utterly vital the best resource is Core, as in, the ability to read it. The order of evaluation is all laid out there. Don [1] and Johan [2] have written variously about it. [1] http://stackoverflow.com/questions/6121146/reading-ghc-core [2] http://blog.johantibell.com/2012/02/forcing-values-returned-from-monadic.htm... -- Kim-Ee On Sat, Dec 1, 2012 at 1:16 AM, Mark Thom wrote:

Haskell's laziness is tricky to understand coming from imperative

...

languages, but once you figure out its evaluation rules, you'll begin to see the elegance.

Is there a paper or other single resource that will help me thoroughly understand non-strictness in Haskell? Once my programs hit a certain level of complexity, their behaviour becomes much harder for me to predict. I've been using the wiki pages up to this point, but apparently they haven't pushed my understanding of laziness nearly far enough.

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Thanks Albert, I believe that's the second time you've helped me this weekend. I'm meiji11 in #haskell. Cheers. On Sun, Dec 2, 2012 at 1:34 PM, Albert Y. C. Lai wrote:

On 12-11-30 01:16 PM, Mark Thom wrote:

...

Is there a paper or other single resource that will help me thoroughly understand non-strictness in Haskell?

See my http://www.vex.net/~trebla/**haskell/lazy.xhtmlhttp://www.vex.net/~trebla/haskell/lazy.xhtml

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I want to simulate some calculation that does that.For example n-body simulation.Anyway this is solved ;)

Date: Fri, 30 Nov 2012 13:25:57 -0800 Subject: Re: [Haskell-cafe] How to incrementally update list From: kc1956@gmail.com To: bmaxa@hotmail.com CC: haskell-cafe@haskell.org

Why do you want to incrementally update this list a lot of times?

The question would affect the answer you get; i.e. some context (non-monadically speaking). :D

On Wed, Nov 28, 2012 at 3:43 AM, Branimir Maksimovic wrote:

...

Problem is following short program: list = [1,2,3,4,5]

advance l = map (\x -> x+1) l

run 0 s = s run n s = run (n-1) $ advance s

main = do let s = run 50000000 list putStrLn $ show s

I want to incrementally update list lot of times, but don't know how to do this. Since Haskell does not have loops I have to use recursion, but problem is that recursive calls keep previous/state parameter leading to excessive stack.and memory usage. I don't know how to tell Haskell not to keep previous state rather to release so memory consumption becomes managable.

Is there some solution to this problem as I think it is rather common?

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-- -- Regards, KC