selector thunks not working? space leak in standard example
I thought that GHC evaluates "THUNK_SELECTORS" and thus eliminates the space leak in this infamous example [Hughes83][Wadler87][Sparud93]:
module Main where
surprise xs = b1 ++ [0,0] ++ b2
where
(b1,b2) = break (==0) xs
strictFromTo :: Int -> Int -> [Int]
strictFromTo i m = takeWhile (<= m) $ strictFrom i
strictFrom :: Int -> [Int]
strictFrom x = let x' = x + 1 in seq x' $ x' : strictFrom x'
main = print (length $ surprise $ strictFromTo (-1000000) 1)
-- space leak, w/ or w/o optimization
main2 = print (length $ strictFromTo (-1000000) 1)
-- runs in constant space, w/ or w/o optimization
However, this program does not run in constant space, even with -O2. I get the same results on GHC6.6 Mac OS X Intel GHC6.2.1 Linux Intel GHC6.4.1 Linux Intel
Trac metadata
Trac field | Value |
---|---|
Version | 6.6 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Runtime System |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | Multiple |
Architecture |