I have created a ticket for the proposal on GHC's Trac (see here: http://hackage.haskell.org/trac/ghc/ticket/7077). I didn't asked for the maintainer's advice before opening a ticket given that the maintener is libraries@haskell.org and there wasn't any opposition. Based on this list advice, I finally decided to just re-export GHC.Exts's newtype for the proposal's purposes, so that this proposal doesn't get bikeshedded to death on the newtype's name. Regards, ARJANEN Loïc On 2012-06-28 12:01, ARJANEN Loïc Jean David wrote :
Hello all,
I recently noticed that despite conversations about that in this mailing-list, there isn't an order-reversing newtype in Data.Ord. That newtype would be quite useful, e.g. for reverse-sorting a list or a set, so I propose we add a newtype defined thusly:
newtype Reverse a = Reverse { fromReverse :: a } deriving (Eq)
instance Ord a => Ord (Reverse a) where compare (Reverse x) (Reverse y) = compare y x
I took the implementation from the Down newtype in GHC.Exts, so we could perhaps just re-export it. This will cause breakage to code already defining a type named Reverse, so I don't know if the damage will be important. Of course, the name and definition are open to discussion.
Deadline: 12 July 2012.
P.S. : A conversation about that took place here: http://haskell.1045720.n5.nabble.com/A-Down-newtype-in-Data-Ord-td5005373.ht...
-- ARJANEN Loïc Jean David http://blog.luigiscorner.com --- "Computer science is no more about computers than astronomy is about telescopes, biology is about microscopes, or chemistry is about beakers and test tubes. Science is not about tools. It is about how we use them, and what we find out when we do." Michael R. Fellows and Ian Parberry