<font face="verdana,sans-serif">Here's a version that works:<br><br><b>import Control.DeepSeq</b><br></font><br><div><div>list = [1,2,3,4,5]</div><div><br></div><div>advance l = <b>force $</b> map (\x -> x+1) l</div>
<div><br></div><div>run 0 s = s</div><div>run n s = run (n-1) $ advance s</div><div><br></div><div>main = do</div><div> let s = run 50000000 list</div><div> putStrLn $ show s<br><br>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.<br>
<br>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.<br><br>Ηope this helps,<br> - Clark<br></div></div>
<div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Nov 28, 2012 at 7:07 AM, Benjamin Edwards <span dir="ltr"><<a href="mailto:edwards.benj@gmail.com" target="_blank">edwards.benj@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir="ltr">TCO + strictnesses annotations should take care of your problem.</p>
<div class="gmail_quote"><div><div class="h5">On 28 Nov 2012 11:44, "Branimir Maksimovic" <<a href="mailto:bmaxa@hotmail.com" target="_blank">bmaxa@hotmail.com</a>> wrote:<br type="attribution"></div></div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5">
<div><div dir="ltr">
Problem is following short program:<div><div>list = [1,2,3,4,5]</div><div><br></div><div>advance l = map (\x -> x+1) l</div><div><br></div><div>run 0 s = s</div><div>run n s = run (n-1) $ advance s</div><div><br></div>
<div>main = do</div><div> let s = run 50000000 list</div><div> putStrLn $ show s</div></div><div><br></div><div>I want to incrementally update list lot of times, but don't know</div><div>how to do this.</div>
<div>Since Haskell does not have loops I have to use recursion,</div><div>but problem is that recursive calls keep previous/state parameter</div><div>leading to excessive stack.and memory usage.</div><div>I don't know how to tell Haskell not to keep previous</div>
<div>state rather to release so memory consumption becomes</div><div>managable.</div><div><br></div><div>Is there some solution to this problem as I think it is rather</div><div>common?</div><div><br></div> </div>
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