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{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeOperators #-}
module Main where
import Data.Proxy (Proxy(..))
import GHC.Generics
main :: IO ()
main = do
print (fullyStrict (Proxy :: Proxy (StrictMaybe Bool)))
print (fullyStrict (Proxy :: Proxy (Maybe Bool)))
data StrictMaybe a = StrictNothing | StrictJust !a
deriving (FullyStrict, Generic)
instance FullyStrict Bool
instance FullyStrict a => FullyStrict (Maybe a)
class FullyStrict a where
fullyStrict :: proxy a -> Bool
default fullyStrict :: (GFullyStrict (Rep a)) => proxy a -> Bool
fullyStrict _ = gfullyStrict (Proxy :: Proxy (Rep a p))
class GFullyStrict f where
gfullyStrict :: proxy (f p) -> Bool
instance GFullyStrict V1 where
gfullyStrict _ = True
instance GFullyStrict U1 where
gfullyStrict _ = True
instance FullyStrict c => GFullyStrict (Rec0 c) where
gfullyStrict _ = fullyStrict (Proxy :: Proxy c)
instance GFullyStrict f => GFullyStrict (D1 c f) where
gfullyStrict _ = gfullyStrict (Proxy :: Proxy (f p))
instance GFullyStrict f => GFullyStrict (C1 c f) where
gfullyStrict _ = gfullyStrict (Proxy :: Proxy (f p))
instance (GFullyStrict f, Selector c) => GFullyStrict (S1 c f) where
gfullyStrict _ = gfullyStrict (Proxy :: Proxy (f p))
&& selDecidedStrictness (undefined :: S1 c f p) /= DecidedLazy
instance (GFullyStrict f, GFullyStrict g) => GFullyStrict (f :+: g) where
gfullyStrict _ =
gfullyStrict (Proxy :: Proxy (f p)) && gfullyStrict (Proxy :: Proxy (g p))
instance (GFullyStrict f, GFullyStrict g) => GFullyStrict (f :*: g) where
gfullyStrict _ =
gfullyStrict (Proxy :: Proxy (f p)) && gfullyStrict (Proxy :: Proxy (g p))
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