Hi hoping someone can shed some light on this: The following code causes a "C stack overflow" in hugs (version 20051031) but not in ghc (version 6.6) The point of the exercise is to process a very large file lazily, returning the consumed and unconsumed parts (i.e. basic parser combinators). The simplified (stylised example of the problem) is displayed bellow. test1 (on a large file) will succeed in ghc but fail in hugs test2 on same file will succeed in both ghc and hugs the problem appears to be retaining a hold on the unconsummed portion and returning it. maybe something to do with updating CAFS, all too subtle for me. The question: is there any changes that can be made to the code to make test1 work in hugs without changing the essence of the function.

test1 = readFile "big.dat" >>= (\x->print $ parse x) test2 = readFile "big.dat" >>= (\x->print $ fst $ parse x)

big.dat is just some large data file say 1MB. (not particularly large by todays standards!)

parse x = sqnc item x where

item =( \ ts -> case ts of [] -> ( Nothing, []) ts -> ( Just (head ts), tail ts) )

sqnc p ts = let ( r, ts' ) = p ts in case r of Nothing -> ([],ts') Just x -> let (r',ts'') = (sqnc p ts') in ( x:r', ts'' )

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