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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