[Haskell-cafe] Parsec memory behavior
Juan Carlos Arevalo Baeza
jcab.lists at JCABs-Rumblings.com
Wed May 17 14:36:00 EDT 2006
Try this simple program:
ppAny = tokenPrim show (\p _ _ -> p) (\t -> Just t)
ppTest = many ppAny
p s =
case runParser ppTest True "" s of
Left error -> show error
Right result -> result
main = do let fname = "C:/main.i"
f <- readFile fname
let tokens = p f
putStrLn . show $ head tokens
This is the simplest expression of using Parsec, it just returns the
input unchanged. But it already seems to have a big memory leak. When
parsing a 2 MB file, I'm seeing the program grow in size up to about 160
MB before it ends.
I assume this is known behavior. I believe it's because of the way
Parsec deals with errors: when you chain two parsers in sequence, the
result of the first one (in this case the head of the list) is not
available until it knows if the second one failed or not.
Is there any known alternative that doesn't exhibit this behavior? It
would have to somehow return errors inline or on a "side channel". I'll
be toying with this sort of thing for a while.
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