[Haskell-cafe] Failure and comonads

[Einar Karttunen]

Hello

With the resent discussion on comonads on #haskell (mostly due to Uustalo's
excellent paper) I am wondering is it possible to model failure with 
comonads?

It seems to me that Reader,Writer and State can be implemented with both
monads and comonads. IO can be implemented as a monad but OI wants 
linear types. Streams make fine comonads. Is there anything corresponding
to Maybe or List?

- Einar Karttunen