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Talk:Functor hierarchy proposal

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Revision as of 21:46, 15 January 2007 by Twanvl (Talk | contribs)

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Um, it would be good if it was something like:

class (Idiom f) => Monad f where
  fmap f m = m >>= return . f -- or ap . return ?
  ap mf mv = mf >>= \f -> mv >>= \v -> return $ f v
  (>>=) :: f a -> (a -> f b) -> f b

Or am I missing the point?

Serhei 15:24, 29 January 2006 (UTC)

You can't put defaults for one class in another. Though that could be another proposal. —Ashley Y 21:02, 29 January 2006 (UTC)
Wasn't this part of John Meacham's class system proposal? What happend to this? -- Wolfgang Jeltsch 19:25, 2 February 2006 (UTC)
<*>
should really be merged with
ap
, right ? (Btw, why such a symmetric operator symbol as
<*>
 ?
<*
or some other assymetric one would be better .. even plain
`ap`
is not so bad, imho.) Also, it would be nice to change
sequence
,
sequence_
,
mapM
and
mapM_
to only require
Applicative
instead of
Monad
. (Or one could merge these four into something like
Data.FunctorM.FunctorM
, which should use
Applicative
anyway.) -- StefanLjungstrand 10:18, 3 November 2006 (UTC)

I think it makes sense to take return out of Applicative. Either into a separate step between Functor and Applicative, or into a new class altogether:

class Boxable f where
     return :: a -> f a
class (Functor f, Boxable f) => Applicative f where
     ...

But maybe this is just overengineering.

Twanvl 21:46, 15 January 2007 (UTC)