[Haskell-cafe] two problems with Data.Binary and Data.ByteString

[Bertram Felgenhauer]

Tim Newsham wrote:
[snip]
> I would have expected this to fix my problems:
>
>   binEof :: Get ()
>   binEof = do
>       more <- not <$> isEmpty
>       when more $ error "expected EOF"
>
>   decodeFully :: Binary b => B.ByteString -> b
>   decodeFully = runGet (get << binEof)
>     where a << b = a >>= (\x -> b >> return x)

Remember that the Get monad is lazy; the result of binEof is never
used, so the action is not performed.

decodeFully :: Binary b => B.ByteString -> b
decodeFully = runGet (get << binEof)
  where a << b = a >>= (\x -> b >>= \y -> y `seq` return x)
works, for example, and also
  where a << b = a >>= (\x -> b >>= \y -> return (y `seq` x))
and
  where (<<) = liftM2 (flip seq)

HTH,

Bertram