M

pemis.hs

instance (Enum a, Num a) => Num [a] where
  (*) = liftA2 (*)
  fromInteger n = [1..fromInteger n]

instance (Enum a, Real a) => Real [a] where
instance Enum [a] where

instance Integral a => Integral [a] where
  mod = liftA2 mod

instance (Applicative m, Integral (m a), Reifies s a) => Num (TaggedT s m a) where
  TaggedT x * TaggedT y = mapTaggedT ((x * y) `mod`) reflexivity
  fromInteger = tag . fromInteger

-- >>> weirdo 11 (4 × 7)
-- [1,2,3,4,5,6,7,2,4,6,8,10,1,3,3,6,9,1,4,7,10,4,8,1,5,9,2,6]
weirdo :: Int -> (forall s. Reifies s Int => TaggedT s [] Int) -> [Int]
weirdo n z = reify n (untag . asProxyOf z)

asProxyOf :: p s m a -> Proxy s -> p s m a
asProxyOf a _ = a