The FunctorM library
hallgren at cse.ogi.edu
Wed Mar 23 22:14:41 EST 2005
Iavor Diatchki wrote:
>Just to avoid confusion I think the suggestions were:
>class Functor f => Monad f where ...
>class Functor f => FunctorM f where ...
>I know the first one differs from the Haskell report, but perhaps this
>is a flaw in the library design that should be fixed.
Yes, I think this should be fixed, and perhaps it could be done in a
backward compatible way? If classes were allowed to declare default
methods for superclasses, then you could have
class Functor f where fmap :: ...
class Functor m => Monad m where
...the usual stuff...
fmap = liftM
instance Monad T where ...
for some T, would implicitly introduce an instance Functor T, if it is
not defined explicitly...
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