Instance classes and error (also, related to Data.Binary.GET)
I am using the Data.Binary module and having some issues reading big endian files (actually, just reading the file). I can read the header but not the rest of the data which contains a set of row information. Also, go ahead and make fun my style of coding. Anyway, This is the my code and the error at the bottom. The issue stems from here, it says I didn't define an instance, but I did: instance Binary URLSet where put _ = do BinaryPut.putWord8 0 get = do remainingByteData <- BinaryGet.getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData x :: KeywordsInfo <- decode remainingByteData return (URLSet {urlinfo=i, titleinfo=j, descrinfo=k, keywordsinfo=x}) ----- module Main where import Data.Word import Data.Binary import qualified Data.ByteString.Lazy.Char8 as BSLC8 import Data.ByteString.Lazy (ByteString) import Data.Binary.Get as BinaryGet import Data.Binary.Put as BinaryPut import IO import Text.Printf import System.Environment import Control.Monad (replicateM, liftM) {- ********************************************************* Define the Database Data Types SpiderDatabase represents a singleton wrapper for an entire database. ********************************************************* -} data SpiderDatabase = SpiderDatabase { magicNumberA :: Word16, magicNumberB :: Word16, majorVers :: Word16, minorVers :: Word16, headerTag :: Word16, poolLen :: Word16, spiderpool :: [URLSet] } data URLSet = URLSet { urlinfo :: URLInfo, titleinfo :: TitleInfo, descrinfo :: DescrInfo, keywordsinfo :: KeywordsInfo } data URLInfo = URLInfo { tag :: Word8, urlid :: Word16, urllen :: Word16, url :: ByteString } data TitleInfo = TitleInfo { titletag :: Word8, titlelen :: Word16, title :: ByteString } data DescrInfo = DescrInfo { descrtag :: Word8, descrlen :: Word16, descr :: ByteString } data KeywordsInfo = KeywordsInfo { keywordstag :: Word8, keywordslen :: Word16, keywords :: ByteString } {- ********************************************************* Class instances ********************************************************* -} instance Show SpiderDatabase where show db = let magicb = (magicNumberB db) header = (headerTag db) poolct = (poolLen db) in "<<<Database Content>>>\n" ++ (((printf "Magic: %X %X\n") (magicNumberA db)) (magicNumberB db)) ++ printf "URL Pool Count: %d\n" poolct ++ "<<<End>>>" instance Binary URLInfo where put _ = do BinaryPut.putWord8 0 get = do urltag <- getWord8 idx <- getWord16be len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (URLInfo {tag=urltag, urlid=idx, urllen=len, url=strdata}) instance Binary DescrInfo where put _ = do BinaryPut.putWord8 0 get = do tag <- getWord8 len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (DescrInfo {descrtag=tag, descrlen=len, descr=strdata}) instance Binary TitleInfo where put _ = do BinaryPut.putWord8 0 get = do tag <- getWord8 len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (TitleInfo {titletag=tag, titlelen=len, title=strdata}) instance Binary KeywordsInfo where put _ = do BinaryPut.putWord8 0 get = do tag <- getWord8 len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (KeywordsInfo {keywordstag=tag, keywordslen=len, keywords=strdata}) instance Binary URLSet where put _ = do BinaryPut.putWord8 0 get = do remainingByteData <- BinaryGet.getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData x :: KeywordsInfo <- decode remainingByteData return (URLSet {urlinfo=i, titleinfo=j, descrinfo=k, keywordsinfo=x}) instance Binary SpiderDatabase where put _ = do BinaryPut.putWord8 0 get = do magicnumbera <- BinaryGet.getWord16be magicnumberb <- BinaryGet.getWord16be major <- BinaryGet.getWord16be minor <- BinaryGet.getWord16be header <- BinaryGet.getWord16be poolct <- BinaryGet.getWord16be -- ******************************* -- Get the remaining byte string data, -- So that we can use lazy bytestring to load to load the -- the data types. -- ******************************* remainingByteData <- BinaryGet.getRemainingLazyByteString -- pool <- (replicate (fromIntegral poolct) (decode remainingByteData)) z :: URLSet <- decode remainingByteData return (SpiderDatabase {magicNumberA=magicnumbera, magicNumberB=magicnumberb, majorVers=major, minorVers=minor, headerTag=header, poolLen=poolct }) main = do putStrLn "Running Spider Database Reader" args <- getArgs db :: SpiderDatabase <- decodeFile (args !! 0) putStrLn $ show db putStrLn "Done" *** *** Error: DbReader.hs:119:22: No instance for (Binary (Get URLInfo)) arising from a use of `decode' at DbReader.hs:119:22-45 Possible fix: add an instance declaration for (Binary (Get URLInfo)) In a 'do' expression: i :: URLInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData .... DbReader.hs:120:24: No instance for (Binary (Get TitleInfo)) arising from a use of `decode' at DbReader.hs:120:24-47 Possible fix: add an instance declaration for (Binary (Get TitleInfo)) In a 'do' expression: j :: TitleInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData .... DbReader.hs:121:24: No instance for (Binary (Get DescrInfo)) arising from a use of `decode' at DbReader.hs:121:24-47 Possible fix: add an instance declaration for (Binary (Get DescrInfo)) In a 'do' expression: k :: DescrInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData .... DbReader.hs:122:27: No instance for (Binary (Get KeywordsInfo)) arising from a use of `decode' at DbReader.hs:122:27-50 Possible fix: add an instance declaration for (Binary (Get KeywordsInfo)) In a 'do' expression: x :: KeywordsInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData .... DbReader.hs:142:21: No instance for (Binary (Get URLSet)) arising from a use of `decode' at DbReader.hs:142:21-44 Possible fix: add an instance declaration for (Binary (Get URLSet)) In a 'do' expression: z :: URLSet <- decode remainingByteData In the expression: do magicnumbera <- getWord16be magicnumberb <- getWord16be major <- getWord16be minor <- getWord16be .... In the definition of `get': get = do magicnumbera <- getWord16be magicnumberb <- getWord16be major <- getWord16be .... make: *** [dbreader] Error 1 -- Berlin Brown [berlin dot brown at gmail dot com] http://botspiritcompany.com/botlist/?
I've no experience with Data.Binary, but I noticed you declared instance Binary YourType where... and the compiler says instance Binary (Get YourType) is missing. That might be worth looking into. Cheers, Daniel Am Freitag, 4. Januar 2008 00:13 schrieb bbrown:
I am using the Data.Binary module and having some issues reading big endian files (actually, just reading the file). I can read the header but not the rest of the data which contains a set of row information. Also, go ahead and make fun my style of coding.
Anyway, This is the my code and the error at the bottom.
The issue stems from here, it says I didn't define an instance, but I did:
instance Binary URLSet where put _ = do BinaryPut.putWord8 0 get = do remainingByteData <- BinaryGet.getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData x :: KeywordsInfo <- decode remainingByteData return (URLSet {urlinfo=i, titleinfo=j, descrinfo=k, keywordsinfo=x})
-----
module Main where
import Data.Word import Data.Binary import qualified Data.ByteString.Lazy.Char8 as BSLC8 import Data.ByteString.Lazy (ByteString) import Data.Binary.Get as BinaryGet import Data.Binary.Put as BinaryPut import IO import Text.Printf import System.Environment import Control.Monad (replicateM, liftM)
{- ********************************************************* Define the Database Data Types SpiderDatabase represents a singleton wrapper for an entire database. ********************************************************* -} data SpiderDatabase = SpiderDatabase { magicNumberA :: Word16, magicNumberB :: Word16, majorVers :: Word16, minorVers :: Word16, headerTag :: Word16, poolLen :: Word16, spiderpool :: [URLSet] } data URLSet = URLSet { urlinfo :: URLInfo, titleinfo :: TitleInfo, descrinfo :: DescrInfo, keywordsinfo :: KeywordsInfo } data URLInfo = URLInfo { tag :: Word8, urlid :: Word16, urllen :: Word16, url :: ByteString } data TitleInfo = TitleInfo { titletag :: Word8, titlelen :: Word16, title :: ByteString } data DescrInfo = DescrInfo { descrtag :: Word8, descrlen :: Word16, descr :: ByteString } data KeywordsInfo = KeywordsInfo { keywordstag :: Word8, keywordslen :: Word16, keywords :: ByteString } {- ********************************************************* Class instances ********************************************************* -} instance Show SpiderDatabase where show db = let magicb = (magicNumberB db) header = (headerTag db) poolct = (poolLen db) in "<<<Database Content>>>\n" ++ (((printf "Magic: %X %X\n") (magicNumberA db)) (magicNumberB db)) ++ printf "URL Pool Count: %d\n" poolct ++ "<<<End>>>"
instance Binary URLInfo where put _ = do BinaryPut.putWord8 0 get = do urltag <- getWord8 idx <- getWord16be len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (URLInfo {tag=urltag, urlid=idx, urllen=len, url=strdata}) instance Binary DescrInfo where put _ = do BinaryPut.putWord8 0 get = do tag <- getWord8 len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (DescrInfo {descrtag=tag, descrlen=len, descr=strdata}) instance Binary TitleInfo where put _ = do BinaryPut.putWord8 0 get = do tag <- getWord8 len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (TitleInfo {titletag=tag, titlelen=len, title=strdata}) instance Binary KeywordsInfo where put _ = do BinaryPut.putWord8 0 get = do tag <- getWord8 len <- getWord16be strdata <- BinaryGet.getLazyByteString (fromIntegral len) return (KeywordsInfo {keywordstag=tag, keywordslen=len, keywords=strdata}) instance Binary URLSet where put _ = do BinaryPut.putWord8 0 get = do remainingByteData <- BinaryGet.getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData x :: KeywordsInfo <- decode remainingByteData return (URLSet {urlinfo=i, titleinfo=j, descrinfo=k, keywordsinfo=x})
instance Binary SpiderDatabase where put _ = do BinaryPut.putWord8 0 get = do magicnumbera <- BinaryGet.getWord16be magicnumberb <- BinaryGet.getWord16be major <- BinaryGet.getWord16be minor <- BinaryGet.getWord16be header <- BinaryGet.getWord16be poolct <- BinaryGet.getWord16be -- ******************************* -- Get the remaining byte string data, -- So that we can use lazy bytestring to load to load the -- the data types. -- ******************************* remainingByteData <- BinaryGet.getRemainingLazyByteString -- pool <- (replicate (fromIntegral poolct) (decode remainingByteData)) z :: URLSet <- decode remainingByteData return (SpiderDatabase {magicNumberA=magicnumbera, magicNumberB=magicnumberb, majorVers=major, minorVers=minor, headerTag=header, poolLen=poolct }) main = do putStrLn "Running Spider Database Reader" args <- getArgs db :: SpiderDatabase <- decodeFile (args !! 0) putStrLn $ show db putStrLn "Done"
*** *** Error:
DbReader.hs:119:22: No instance for (Binary (Get URLInfo)) arising from a use of `decode' at DbReader.hs:119:22-45 Possible fix: add an instance declaration for (Binary (Get URLInfo)) In a 'do' expression: i :: URLInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData ....
DbReader.hs:120:24: No instance for (Binary (Get TitleInfo)) arising from a use of `decode' at DbReader.hs:120:24-47 Possible fix: add an instance declaration for (Binary (Get TitleInfo)) In a 'do' expression: j :: TitleInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData ....
DbReader.hs:121:24: No instance for (Binary (Get DescrInfo)) arising from a use of `decode' at DbReader.hs:121:24-47 Possible fix: add an instance declaration for (Binary (Get DescrInfo)) In a 'do' expression: k :: DescrInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData ....
DbReader.hs:122:27: No instance for (Binary (Get KeywordsInfo)) arising from a use of `decode' at DbReader.hs:122:27-50 Possible fix: add an instance declaration for (Binary (Get KeywordsInfo)) In a 'do' expression: x :: KeywordsInfo <- decode remainingByteData In the expression: do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData .... In the definition of `get': get = do remainingByteData <- getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData ....
DbReader.hs:142:21: No instance for (Binary (Get URLSet)) arising from a use of `decode' at DbReader.hs:142:21-44 Possible fix: add an instance declaration for (Binary (Get URLSet)) In a 'do' expression: z :: URLSet <- decode remainingByteData In the expression: do magicnumbera <- getWord16be magicnumberb <- getWord16be major <- getWord16be minor <- getWord16be .... In the definition of `get': get = do magicnumbera <- getWord16be magicnumberb <- getWord16be major <- getWord16be .... make: *** [dbreader] Error 1
-- Berlin Brown [berlin dot brown at gmail dot com] http://botspiritcompany.com/botlist/?
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On Jan 3, 2008, at 18:13 , bbrown wrote:
DbReader.hs:119:22: No instance for (Binary (Get URLInfo)) arising from a use of `decode' at DbReader.hs:119:22-45
Without looking more closely, this suggests to me that you have mismatched or incorrectly encapsulated monads (for example, treating a value in the Get monad as if it were pure). This might be related to the way you specify the types of the values obtained from decode. (I haven't used Data.Binary.) -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH
Like the previous no experience with Data.Binary, but my (rusty) monad experience is enough to see the source of the problem: bbrown wrote:
The issue stems from here, it says I didn't define an instance, but I did:
instance Binary URLSet where put _ = do BinaryPut.putWord8 0 get = do remainingByteData <- BinaryGet.getRemainingLazyByteString i :: URLInfo <- decode remainingByteData j :: TitleInfo <- decode remainingByteData k :: DescrInfo <- decode remainingByteData x :: KeywordsInfo <- decode remainingByteData return (URLSet {urlinfo=i, titleinfo=j, descrinfo=k, keywordsinfo=x})
Data.Binary seems to use the Get monad which looks to be a garden variety parsing monad. For line in the do block: i :: URLInfo <- decode remainingByteData Because of the way do notation works x::a <- is expecting a value of M a for a monad M, above Get URLInfo, inplying a type of ByteString -> (Get URLInfo) for decode and therefore the comiler is looking for the corresponding Binary instance (and of course, not finding it since, quite properly, your binary instance is URLInfo not Get URLInfo). If you can't follow this, find a monad tutorial and look at how do notation expands to >>= and >>. The code you have almost certainly isn't doing what you want/expect (even if you fix the bad monad nesting you are trying to repeatedly decode the same data as different types). Not knowing exactly how your data is encoded it is hard to be certain of the correct code but something like this seems more likely (untried): instance Binary URLSet where put _ = do BinaryPut.putWord8 0 get = do i :: URLInfo <- get j :: TitleInfo <- get k :: DescrInfo <- get x :: KeywordsInfo <- get return (URLSet {urlinfo=i, titleinfo=j, descrinfo=k, keywordsinfo=x}) This assumes that the data contains the structures serialized in order. In this case for i the type of get is inferred to Get URLInfo - which will work since URLInfo has a Binary instance. You also have a similar issue in the SpiderDatabase instance. Clive
participants (4)
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bbrown -
Brandon S. Allbery KF8NH -
Clive Brettingham-Moore -
Daniel Fischer