At 10:15 06/12/04 +0000, Simon Peyton-Jones wrote:

| This is where I find ghc's newtype deriving to be incredibly useful. | | newtype CPError a = CPError (Either Error a) | deriving(Monad,MonadError) | | now CPError is a monad and an instance of MonadError and you are free to | override or inherit more interesting instances at will without | conflicting with the basic types for Either :)

Aha! I've always wondered whether anyone uses this feature, which I implemented at John Hughes's suggestion. I'd be interested to know if you are alone, or whether others do so too.

Not a user, but sounds maybe interesting. Can you point to documentation? #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact