Similarly, I'm using the following to get around type parameters that don't
provide Bounded:
data AddBounds a = MinBound | NoBound a | MaxBound
deriving (Eq, Ord, Read, Show)
instance Bounded (AddBounds a) where
minBound = MinBound
maxBound = MaxBound
On Dec 2, 2007 3:25 PM, Ross Paterson
On Sun, Dec 02, 2007 at 09:57:50AM -0800, Conal Elliott wrote:
My proposed addition:
-- | Ordered monoid under 'max'. newtype Max a = Max { getMax :: a } deriving (Eq, Ord, Read, Show, Bounded)
instance (Ord a, Bounded a) => Monoid (Max a) where mempty = Max minBound Max a `mappend` Max b = Max (a `max` b)
Funny, I was thinking of proposing a Max type that adjoined a synthetic identity, as we did in the finger tree paper:
data Max a = NoMax | Max a deriving (Eq, Ord, Read, Show)
instance Ord a => Monoid (Max a) where mempty = NoMax NoMax `mappend` b = b a `mappend` NoMax = a Max x `mappend` Max y = Max (x `max` y)
and similarly for Min. One could even define
getMax :: Bounded a => Max a -> a getMax NoMax = minBound getMax (Max x) = x _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries