Re: Monads, Functors and typeclasses

[Alex Ferguson]

Koen Claessen:
> In fact, the connection between Monad and Functor is much stronger than
> the connection between MonadZero and Monad; the former relation can be
> expressed in terms of a direct default definition.

But alas, not in Haskell; this would be possible, though, if the
rules against circular instance declarations and overlapping
instances were relaxed, though.  The question is though, does this
happen sufficiently often (a subtype instance completely determining
its supertype's methods) to be worth bending the language sufficiently
to admit it?

Slainte,
Alex.