Hi,
I'm getting the compile error:
Gamgine/Image/PNG/Internal/Parser.hs:14:10:
Functional dependencies conflict between instance declarations:
instance Monad m => Stream LB.ByteString m Word8
-- Defined at Gamgine/Image/PNG/Internal/Parser.hs:14:10
instance Monad m => Stream LB.ByteString m Char
-- Defined in ‘Text.Parsec.Prim’
The relevant stuff from the parsec 3.1.9 code[1] is:
{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleContexts,
UndecidableInstances #-}
...
import qualified Data.ByteString.Lazy.Char8 as CL
import qualified Data.ByteString.Char8 as C
...
class (Monad m) => Stream s m t | s -> t where
uncons :: s -> m (Maybe (t,s))
instance (Monad m) => Stream CL.ByteString m Char where
uncons = return . CL.uncons
instance (Monad m) => Stream C.ByteString m Char where
uncons = return . C.uncons
And from my code[2] is:
{-# LANGUAGE BangPatterns, FlexibleInstances, MultiParamTypeClasses,
FlexibleContexts #-}
...
import qualified Data.ByteString.Lazy as LB
...
instance (Monad m) => Stream LB.ByteString m Word8 where
uncons = return . LB.uncons
As you can see, the instances are for different ByteString types,
therefore I don't quite get where GHC sees here any conflicts.
Greetings,
Daniel
[1] https://github.com/aslatter/parsec/blob/master/Text/Parsec/Prim.hs
[2]
https://github.com/dan-t/Gamgine/blob/master/Gamgine/Image/PNG/Internal/Parser.hs
_______________________________________________
Glasgow-haskell-users mailing list
Glasgow-haskell-users@haskell.org
http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users
