Hi Jake
https://hackage.haskell.org/package/applicative-numbers can generate those
instances.
Regards
Adam
On Apr 22, 2016 10:23 AM, "Jake"
Is it possible to automatically derive instances of Numeric type classes like Num, Fractional, Real, Floating, etc?
I currently have two datatypes, Pair and Triple, that are defined like this:
data Pair a = Pair a a data Triple a = Triple a a a
I wrote these pretty trivial instances for Num and Floating:
instance Num a => Num (Pair a) where (+) = liftA2 (+) (*) = liftA2 (*) abs = liftA abs negate = liftA negate signum = liftA signum fromInteger = pure . fromInteger
instance Fractional a => Fractional (Pair a) where (/) = liftA2 (/) recip = liftA recip fromRational = pure . fromRational
and practically identical instances for Triple as well.
Is there anyway to have GHC derive these instances and the other numeric type classes?
Thanks, Jake
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