Re: [web-devel] Automatically making every Cereal.Serialize instance of PersistField - bad idea?

28 Jan 2011

      I should have added, as long as the type-checker terminates and doesn't go into an infinite loop, is there any danger in doing this?

On Jan 28, 2011, at 2:24 PM, Max Cantor wrote:
...
With a bit of code, you can save a lot of effort if you add new types to Persistent:
instance Cereal.Serialize a => PersistField a where
 toPersistValue a = PersistByteString $ Cereal.encode a
 fromPersistValue (PersistByteString b) = Cereal.decode b
 fromPersistValue _ = Left "bad type for cereal encoded data"
 sqlType _ = SqlBlob
 isNullable _ = False
BUT, this requires UndecidableInstances.  Is this a bad idea?
mc