Kuncak writes:
> Why don't we have "deriving Functor" in Haskell?
>
> Functor is in Prelude, so it could be known to the compiler.
> I am aware that one does not write modular interpreter every day,
> but I think that turning a type constructor into functor is something
> which is done quite often.
>
> Am I missing something or is it just not important enough?
Hi.
I don't know how significant this is, but types declared as Functor
instances have kind (*->*), whereas types with any derived instances
have kind *. Perhaps those extra variables in fmap's type make
matters more complicated.
Regards,
Tom
