Haskell Space Overflow

Question

I\'ve compiled this program and am trying to run it.

import Data.List
import Data.Ord
import qualified Data.MemoCombinators as Memo

collatzLength :: Int -&g         


        

Answer 1

Here's a shorter program that fails in the same way:

main = print (maximum [0..1000000])

Yep.

$ ghc --make harmless.hs && ./harmless
[1 of 1] Compiling Main             ( harmless.hs, harmless.o )
Linking harmless ...
Stack space overflow: current size 8388608 bytes.
Use `+RTS -Ksize -RTS' to increase it.

With -O2 it works. What do I make of it? I don't know :( These space mysteries are a serious gotcha.

Edit:

Thx to hammar for pointing out the culprit.

Changing your program to use

maximum' = foldl1' max

Makes it work without -O2. The implementation of Prelude's maximum is lazy and so doesn't quite work for long lists without compiler magic dust.