[Haskell-cafe] Strange error when using Attoparsec and Enumerator
crutcher at gmail.com
Sun Dec 5 21:55:35 CET 2010
Oh thank you!
I can't believe the number of times I read through that code without
On Sun, Dec 5, 2010 at 12:49 PM, John Millikin <jmillikin at gmail.com> wrote:
> I swear attoparsec-enumerator is going to give me grey hair; the error
> you're receiving is because iterParser itself is divergent. Fixed in
> 0.2.0.3, with my sincere apologies.
> On Sun, Dec 5, 2010 at 09:14, Crutcher Dunnavant <crutcher at gmail.com> wrote:
>> I have spent a good chunk of the past week tracing code, trying to
>> solve this problem. I'm seeing an error when using Enumerator and
>> Attoparsec that I can't explain. This is a reduced form of the
>> In general, I've observed that debugging broken iterators and
>> enumerators is very hard. We probably want some tooling around that;
>> I'm looking at an identity enumeratee with debug.trace shoved in, or
>> something like that, not sure yet what would help.
>> Haskell 2010, ghc 6.12.3
>> import Control.Applicative ((<|>))
>> import qualified Data.Attoparsec.Char8 as AP
>> import qualified Data.Attoparsec.Combinator as APC
>> import qualified Data.Attoparsec.Enumerator as APE
>> import qualified Data.ByteString.Char8 as B
>> import qualified Data.Enumerator as E
>> import Data.Enumerator (($$))
>> import System.IO as IO
>> parseLine :: AP.Parser B.ByteString
>> parseLine = do
>> AP.char '+'
>> return . B.pack =<< APC.manyTill AP.anyChar endOfLineOrInput
>> endOfLineOrInput :: AP.Parser ()
>> endOfLineOrInput = AP.endOfInput <|> AP.endOfLine
>> pp :: Show a => AP.Parser a -> String -> IO ()
>> pp p s = do
>> result <- E.run $
>> E.enumList 1 [ B.pack s ]
>> $$ E.sequence (APE.iterParser p)
>> $$ E.printChunks False
>> case result of
>> (Right _) -> return ()
>> (Left e) -> IO.hPutStrLn stderr $ show e
>> main = pp parseLine "+OK"
>> Observed output:
>> *** Exception: enumEOF: divergent iteratee
>> Problems with this:
>> 1) I didn't write an iteratee, enumerator, or enumeratee in this code.
>> Something's wrong.
>> 2) If the parser is divergent, I _should_ be getting the error message:
>> "iterParser: divergent parser"
>> Crutcher Dunnavant <crutcher at gmail.com>
>> Haskell-Cafe mailing list
>> Haskell-Cafe at haskell.org
Crutcher Dunnavant <crutcher at gmail.com>
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