Question

I’ve been playing with newtype wrappers for my indexes to avoid bugs, and I have some code like this:

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

newtype PersonIdx = PersonIdx Int
  deriving (Enum, Eq, Integral, Num, Ord, Real, Show)

To derive Integral, one must derive all its dependencies as well (hence the above list of type-classes).

Is there a way to make it derive all the dependencies of Integral along with it? I would imagine something like:

newtype PersonIdx = PersonIdx Int
  deriving (Integral(..))

Answer 1

No, there is no shortcut. You’ll have to derive from all dependent typeclasses explicitly, but can easily find these by typing :i Integral in ghci.