Yousry Abdallah <[EMAIL PROTECTED]> writes:
> the following program produces a space leak:
Yes, it does. GHC's definition of findIndices is the following:
findIndices :: (a -> Bool) -> [a] -> [Int]
findIndices p xs = [ i | (x,i) <- zip xs [0..], p x]
which has a problem: the large CAF created by [0..], which GHC
erroneously seems to pull out to the top level. My definition of
findIndices would be:
findIndices' :: (a -> Bool) -> [a] -> [Int]
findIndices' p xs = loop 0# p xs
where
loop n p [] = []
loop n p (x:xs) | p x = I# n : loop (n +# 1#) p xs
| otherwise = loop (n +# 1#) p xs
See, much nicer :-)
The CAF problem will be fixed at some point in the future, we are
currently rewriting GHC's run-time system with support for garbage
collection of CAF's (amongst other things).
Cheers,
Simon
--
Simon Marlow [EMAIL PROTECTED]
University of Glasgow http://www.dcs.gla.ac.uk/~simonm/
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