Levity-polymorphic Num typeclass

LevNum.hs

{-# LANGUAGE MagicHash #-}
{-# LANGUAGE TypeInType #-}

module LevNum where

import GHC.Prim
import GHC.Exts (TYPE)

class LevNum (a :: TYPE r) where
  levAdd :: a -> a -> a

instance LevNum Int  where levAdd = (+)
instance LevNum Int# where levAdd = (+#)