Alec Benzer
I was speaking more generally, not specifically about the Haskell typeclasses Num and Enum (although actually irrational numbers aren't enumerable now that I think of it, but I also guess that's a relatively moot point since you can't really represent irrational numbers in a programming language)
There is a Num instance, which doesn't make sense to be an Enum instance: instance Num a => Num (a -> a) where f + g = \x -> f x + g x -- ... This makes some formulas look much nicer and more convenient to write: constOne :: Floating a => a -> a constOne = sin^2 + cos^2 Unfortunately Eq and Show are superclasses of Num, so you need a few bogus instances: instance Eq (a -> a) where (==) = undefined instance Show (a -> a) where show = const "<function>" As an alternative you can do this with the reader functor, too, although it doesn't look nearly as nice for the above formula: constOne :: Floating a => a -> a constOne = (+) <$> (^2) . sin <*> (^2) . cos It looks great for other formulas, though, and is more general: splits :: [a] -> [([a], [a])] splits = zip <$> inits <*> tails Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/