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{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
module Main where
import GHC.Generics hiding (C, C1, D)
import GFunctor
class C1 a where
c1 :: a -> Int
c1 _ = 1
class C2 a where
c21 :: a -> Int
c21 = c22
c22 :: a -> Int
c22 = c21
{-# MINIMAL c21 | c22 #-}
newtype D = D Int deriving C1
instance C1 Int where c1 _ = 2
newtype F a = F1 [a]
deriving (Show, Eq, Generic, Generic1, GFunctor)
data G = G1 deriving (C1)
data H = H1 deriving (C2)
main = print (c1 (D 3))
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