On Aug 27, 2010, at 11:12 AM, Heinrich Apfelmus wrote:
Is it actually necessary to use a type class here? The situation is very similar to
Luke Palmer. Haskell Antipattern: Existential Typeclass. http://lukepalmer.wordpress.com/2010/01/24/
I suggest to use good old data types
data Key = Key { encrypt :: B.ByteString -> B.ByteString, decrypt :: B.ByteString -> B.ByteString, keyLength :: BitLength, serialize :: B.ByteString}
rsa :: RandomGen g => BitLength -> g -> ((Key,Key), g)
In general, I like this approach, but what are encrypt privateKey or decrypt publicKey supposed to do? A type-class solution also does not *prevent* programmers to perform such non-sensical calls, but the data-type solution *forces* programmers to provide non-sensical encrypt and decrypt functions when creating the public and private keys.
class (Binary p, Serialize p) => AsymCipher p where generateKeypair :: RandomGen g => g -> BitLength -> Maybe ((p,p),g) encryptAsym :: p -> B.ByteString -> B.ByteString decryptAsym :: p -> B.ByteString -> B.ByteString asymKeyLength :: p -> BitLength
Why not use generateKeypair :: MonadRandom m => BitLength -> m (Maybe (p,p)) where MonadRandom is from [1]. Sebastian [1]: http://hackage.haskell.org/package/MonadRandom -- Underestimating the novelty of the future is a time-honored tradition. (D.G.)