Would it be an accurate summary of this thread that people are asking for (not including quibbles about naming and a few types): class Ord a => Enum a where succ :: a -> a pred :: a -> a fromEnum :: a -> Int(eger) toEnum :: Int(eger) -> a -- No instance for Float/Double class Ord a => Range a where rangeFromTo :: a -> a -> [a] -- subsumes Ix.range / Enum.enumFromTo rangeFromThenTo :: a -> a -> a -> [a] inRange :: (a, a) -> a -> Bool -- Does have instances for Float/Double. List ranges desugar to this. -- Also has instances for tuples class Range a => InfiniteRange a where -- [1] rangeFrom :: a -> [a] rangeFromThen :: a -> a -> [a] -- Has instances for Float/Double -- No instances for tuples class Range a => Ix a where index :: (a, a) -> a -> Int rangeSize :: (a, a) -> Int -- Again no instances for Float/Double. Having an instance here implies -- that the rangeFrom* are "complete", containing all 'inRange' values class (RealFrac a, Floating a) => RealFloat a where ... -- existing stuff (.<.), (.<=.), (.>.), (.>=.), (.==.) :: a -> a -> Bool -- these are IEEE semantics when applicable instance Ord Float where ... -- real Ord instance where NaN has a place There would be the obvious properties stated for types that are instances of both Enum and Range, but this allows for non-Enum types to still be Range instances. If there's general agreement on this, then we at least have a proposal, and one that doesn't massively complicate the existing system. The next step, I suppose would be to implement it in an AltPrelude module and (sadly, since Enum is changing meaning) a trivial GHC language extension. Then the real hard work of convincing more people to use it would start. If that succeeds, the next hard work would be finding a compatible way to make the transition... I'm not happy with InfiniteRange, but I imagine the alternative (runtime errors) won't be popular in the present crowd. -- Chris