[Haskell-cafe] trying to understand out of memory exceptions
aeyakovenko at gmail.com
Tue Apr 16 20:03:43 CEST 2013
-- So why does this code run out of memory?
import qualified Data.ByteString.Char8 as BS
scanl' :: NFData a => (a -> b -> a) -> a -> [b] -> [a]
scanl' f q ls = q : (case ls of
 -> 
x:xs -> let q' = f q x
in q' `deepseq` scanl' f q' xs)
main = do
file <- openBinaryFile "/dev/zero" ReadMode
chars <- BS.hGetContents file
let rv = drop 100000000000 $ scanl' (+) 0 $ map fromEnum $ BS.unpack
print (head rv)
-- my scanl' implementation seems to do the right thing, because
main = print $ last $ scanl' (+) (0::Int) [0..]
-- runs without blowing up. so am i creating a some thunk here? or is
hGetContents storing values? any way to get the exception handler to print
a trace of what caused the allocation?
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Haskell-Cafe