Hello everyone- I'm working on some project Euler problems today, and I'm stuck on one. It's not the problem itself that's the problem, it's that finding the maximum of a list makes me run out of heap space! http://projecteuler.net/index.php?section=problems&id=14 my code: import Data.List f :: Int -> Int -> Int f acc x | x == 1 = acc | even x = f (acc + 1) (x `div` 2) | otherwise = f (acc + 1) (3 * x + 1) answer = (foldl' max 0) $ map (f 1) [1 .. 999999] I tried using 'foldl' max ' instead of 'maximum' because I thought that foldl' was supposed to work better than foldl or something...I could be confused on that point. Anyway, here's what I get... / _ \ /\ /\/ __(_) / /_\// /_/ / / | | GHC Interactive, version 6.4, for Haskell 98. / /_\\/ __ / /___| | http://www.haskell.org/ghc/ \____/\/ /_/\____/|_| Type :? for help. Loading package base-1.0 ... linking ... done. Prelude> :l ..\test.hs Compiling Main ( ..\test.hs, interpreted ) Ok, modules loaded: Main. *Main> answer GHC's heap exhausted: current limit is 268435456 bytes; Use the `-M<size>' option to increase the total heap size. I also tried writing a simple 'max' function that I thought was tail recursive, and that that would help. Same error. I'm finding it hard to believe that finding a maximum of a list of a million small integers would cause this kind of overflow...is it really that big of a problem? Any help would be appreciated. I have a feeling I'll run into this problem again in the future.