Hi,
I have a Haskell problem that keeps cropping up and I wondered if there
was any solution/work-around/dirty-hack that could help. I keep wanting
to define class instances for things like Functor or Monad, but with
restrictions on the inner type. I'll explain with an example, because I
{-# LANGUAGE MultiParamTypeClasses #-}
class Returnable m a where ret :: a - m a
class Bindable m a b where bind :: m a - (a - m b) - m b
newtype MOAMonad r m a = MOAMonad ((a - m r) - m r)
instance Monad (MOAMonad r m) where
return x = MOAMonad $ ($ x)
MOAMonad h = f = MOAMonad $ \p - h
This is a recurring problem[1] and I'm still looking for a really
satisfying solution. The only working and non-verbose solution I found
is the one Miguel suggests. Although I'm not too fond of splitting up
the monadic functions into separate type classes. A similar solution is
described
On Sun, Apr 26, 2009 at 03:23:17PM +0200, Thomas van Noort wrote:
This is a recurring problem[1] and I'm still looking for a really
satisfying solution. The only working and non-verbose solution I found is
the one Miguel suggests. Although I'm not too fond of splitting up the
monadic
