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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE ImportQualifiedPost #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
module Main where
import Data.Dependent.EnumMap.Strict qualified as DE
import Data.Dependent.EnumMap.Strict.Internal (coe1)
import Data.Dependent.Sum
import Data.Functor.Const
data Tag = A | B | C
deriving (Show)
data STag tag where
SA :: STag A
SB :: STag B
SC :: STag C
deriving instance Show (STag tag)
instance DE.Enum1 STag where
type Enum1Info STag = Const ()
fromEnum1 = \case
SA -> (0, Const ())
SB -> (1, Const ())
SC -> (2, Const ())
toEnum1 n _ = case n of
0 -> coe1 SA
1 -> coe1 SB
2 -> coe1 SC
_ -> error "invalid tag"
data Value tag where
VA :: Int -> Value A
VB :: Bool -> Value B
VC :: String -> Value c
deriving instance Show (Value tag)
main :: IO ()
main = do
print $ DE.fromList @STag @Value []
print $ DE.fromList [SB :=> VB False, SA :=> VA 3]
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