[Haskell-cafe] Retrospective type-class extension

[Limestraël]

Then it would be:

class Functor f where
    fmap :: (a -> b) -> f a -> f b

class (Functor f) => Pointed f where
    pure :: a -> f a

class (Pointed f) => Applicative f where
    (<*>) :: f (a -> b) -> f a -> f b

class (Applicative f) => Monad f where
    join :: f (f a) -> f a

This would be a great idea, for the sake of logic, first (a monad which is
not a functor doesn't make sense), and also to eliminate redudancy (fmap =
liftM, ap = (<*>), etc.)

2010/5/20 Tony Morris <tonymorris at gmail.com>

> Ivan Miljenovic wrote:
> > On 20 May 2010 14:42, Tony Morris <tonymorris at gmail.com> wrote:
> >
> >> We all know that "class (Functor f) => Monad f" is preferable but its
> >> absence is a historical mistake. We've all probably tried once:
> >>
> >> instance (Functor f) => Monad f where
> >>
> >
> > Do you mean the reverse of this (instance (Monad m) => Functor m where) ?
> >
> Yes.
>
> --
> Tony Morris
> http://tmorris.net/
>
>
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