Re: [Haskell-cafe] Re: Binary [was MD5]

Aaron Denney wrote:

On 2007-11-17, Andrew Coppin wrote:

...

pack8into16 :: [Word8] -> Word16 pack8into32 :: [Word8] -> Word32 unpack16into8 :: Word16 -> [Word8] unpack32into8 :: Word32 -> [Word8] pack8into16s :: [Word8] -> [Word16] pack8into32s :: [Word8] -> [Word32] etc.

I had to write all these myself, by hand, and then check that I got everything the right way round and so forth. (And every now and then I find an edge case where these functions go wrong.)

Well, you know, some of these are really the wrong signatures:

pack8into16 :: (Word8, Word8) -> Word16 pack8into32 :: (Word8, Word8, Word8, Word8) -> Word32 unpack16into8 :: Word16 -> (Word8, Word8) unpack32into8 :: Word32 -> (Word8, Word8, Word8, Word8)

curry the above to taste.

Yeah, but unpack16into8s = concatMap unpack16into8 ;-) Now if you just define some function splitN :: Int -> [x] -> [[x]] (I'm sure we've debated why this isn't defined already...), we can even write pack8into16s = map pack8into16 . splitN 16 And so we continue...