On Wed, Apr 27, 2011 at 09:46:08PM +0200, Maciej Marcin Piechotka wrote:
I believe following should work
class Serializer ObjectA where get = check =<< (ObjectA <$> get <*> get <*> get) where check obj@(ObjectA len id attr) | len < 10 && id == 0 = return obj | otherwise = empty
class Serializer ObjectB where get = check =<< (ObjectB <$> get <*> get <*> get) where check obj@(ObjectB len id attr) | len > 10 && id == 1 = return obj | otherwise = empty
parseEitherAB :: Get (Either ObjectA ObjectB) parseEitherAB = (Left <$> get) <|> (Right <$> get)
Hum, that's still not automatic but using Control.Applictive to write one-liners seems a good-enough solution. I will try it. thanks ,) /john