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{-# LANGUAGE TypeFamilies, StandaloneDeriving, FlexibleInstances, GADTs #-}
module Main where
import Data.Ix
-- Deriving Enum with phantom type parameter
data T a = R | S | T deriving( Enum, Show )
-- Tests that deriving works for data families
data family Foo a
data instance Foo Int
= A | B | C | D
deriving (Eq, Enum)
f :: Foo Int -> Bool
f A = True
f B = False
f _ = True
-- Tests that deriving works for GADTs
data Bar a where
P :: Int -> Bar Int
Q :: Bar Int
deriving instance (Eq (Bar Int))
main = do { print [R .. T]
; print (map f [B .. D])
; print [P 3 == P 3, P 4 == Q] }
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