I suppose I should send my reply to the list ... ---------- Forwarded message ---------- From: Antoine Latter Date: Fri, May 22, 2009 at 5:54 PM Subject: Re: [Haskell-cafe] Data.Binary suboptimal instance To: Khudyakov Alexey On Fri, May 22, 2009 at 4:36 PM, Khudyakov Alexey wrote:

...

You can! - It's again time to point out that Put shouldn't be a monad, but a monoid. But as it is, Put is a Writer monad on top of the Builder monoid. Better use that Builder monoid directly.

Could you elaborate? I didn't quite understand.

Anyway I had similar problem and simply wrote few functions. They encode/decode values of same type element by element. It's lazy enough so code could be written in following style:

Or you could go for the compromise position, where the list can be part of a complex data structure so you're not relying on EOF to find the end. (warning, I don't have my compiler handy so this may not even typecheck) import Control.Monad import Data.Monoid import Data.Binary.Builder import Data.Binary.Get data ChunkedList a    = Cons [a] (ChunkedList a) -- Non-null list    | Nil chunkSize = 50 fromList :: [a] -> ChunkedList a fromList []    = Nil fromList xs    = let (front,back) = splitAt chunkSize xs      in Cons front (fromList back) toList :: ChunkedList a -> [a] toList Nil = [] toList (Cons front back) = front ++ toList back putList :: (a -> Builder) -> [a] -> Builder putList f xs = putChunkedList (fromList xs)  where   putChunkedList Nil    = singleton 0   putChunkedList (Cons front back)    = mconcat      [ singleton (genericLength front)      , mconcat $ map f front      , putChunkedList back      ] getList :: Get a -> Get [a] getList m = toList `liftM` getChunkedList  where  getChunkedList = do    cLen <- getWord8    case cLen of      0 -> return Nil      _ -> Cons `liftM` replicateM (fromIntegral cLen) m `ap` getChunkedList