[Haskell-cafe] Strange error when using Attoparsec and Enumerator
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
problem.
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
array-0.3.0.2
attoparsec-0.8.2.0
attoparsec-enumerator-0.2.0.2
bytestring-0.9.1.7
containers-0.4.0.0
deepseq-1.1.0.2
enumerator-0.4.2
text-0.10.0.0
transformers-0.2.2.0
-}
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)
$$ E.printChunks False
case result of
(Right _) - return ()
(Left e) - IO.hPutStrLn stderr $ show e
main = pp parseLine +OK
{-
Observed output:
[OK]
*** Exception: enumEOF: divergent iteratee
Problems with this:
1) I didn't write an iteratee, enumerator, or enumeratee in this code.
Something's wrong.
2) If the parser is divergent, I _should_ be getting the error message:
iterParser: divergent parser
-}
--
Crutcher Dunnavant crutc...@gmail.com
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Re: [Haskell-cafe] Strange error when using Attoparsec and Enumerator
I swear attoparsec-enumerator is going to give me grey hair; the error
you're receiving is because iterParser itself is divergent. Fixed in
0.2.0.3, with my sincere apologies.
On Sun, Dec 5, 2010 at 09:14, Crutcher Dunnavant crutc...@gmail.com wrote:
I have spent a good chunk of the past week tracing code, trying to
solve this problem. I'm seeing an error when using Enumerator and
Attoparsec that I can't explain. This is a reduced form of the
problem.
In general, I've observed that debugging broken iterators and
enumerators is very hard. We probably want some tooling around that;
I'm looking at an identity enumeratee with debug.trace shoved in, or
something like that, not sure yet what would help.
{-
Haskell 2010, ghc 6.12.3
array-0.3.0.2
attoparsec-0.8.2.0
attoparsec-enumerator-0.2.0.2
bytestring-0.9.1.7
containers-0.4.0.0
deepseq-1.1.0.2
enumerator-0.4.2
text-0.10.0.0
transformers-0.2.2.0
-}
import Control.Applicative ((|))
import qualified Data.Attoparsec.Char8 as AP
import qualified Data.Attoparsec.Combinator as APC
import qualified Data.Attoparsec.Enumerator as APE
import qualified Data.ByteString.Char8 as B
import qualified Data.Enumerator as E
import Data.Enumerator (($$))
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:
[OK]
*** 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 crutc...@gmail.com
___
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Re: [Haskell-cafe] Strange error when using Attoparsec and Enumerator
Oh thank you!
I can't believe the number of times I read through that code without
seeing that.
On Sun, Dec 5, 2010 at 12:49 PM, John Millikin jmilli...@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 crutc...@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
problem.
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
array-0.3.0.2
attoparsec-0.8.2.0
attoparsec-enumerator-0.2.0.2
bytestring-0.9.1.7
containers-0.4.0.0
deepseq-1.1.0.2
enumerator-0.4.2
text-0.10.0.0
transformers-0.2.2.0
-}
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:
[OK]
*** 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 crutc...@gmail.com
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--
Crutcher Dunnavant crutc...@gmail.com
___
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Re: [Haskell-cafe] Strange error when using Attoparsec and Enumerator
On Sun, Dec 5, 2010 at 6:14 PM, Crutcher Dunnavant crutc...@gmail.com wrote: 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. Hi Crutcher, I have some enumerator debug code here: https://github.com/snapframework/snap-core/blob/8c9b7098751784b9d88dff68524ed2558c03c3d8/src/Snap/Internal/Iteratee/Debug.hs It's a little bit snap-specific (uses our debug machinery) but helps me a lot when debugging iteratee stuff. Shouldn't be hard to port. It contains a debug iteratee (which just prints its input to stdout) and an iteratee wrapper which logs its input using the Snap debug mechanism before passing it on to the wrapped iteratee. G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
