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|
{-# LANGUAGE DeriveGeneric #-}
import Data.Hashable
import Data.Hashable.Lifted
import GHC.Generics (Generic)
data Foo
= Foo1 Int Char Bool
| Foo2 String ()
deriving (Eq, Generic)
instance Hashable Foo
data Bar = Bar Double Float
deriving (Eq, Generic)
instance Hashable Bar
-- printHash :: (Hashable a, Show a) => a -> IO ()
-- printHash = print . hash
main :: IO ()
main = do
putStrLn "Hashing Foo1"
print . hash $ Foo1 22 'y' True
putStrLn "Hashing Foo2"
print . hash $ Foo2 "hello" ()
putStrLn "Hashing Bar"
print . hash $ Bar 55.50 9.125
-----------------------------------
-- Higher Rank Hashable Examples --
-----------------------------------
{- TODO:
newtype WriterT w m a = WriterT { runWriterT :: m (a, w) }
data Free f a = Pure a | Free (f (Free f a))
instance (Hashable w, Hashable1 m) => Hashable1 (WriterT w m) where
liftHashWithSalt h s (WriterT m) =
liftHashWithSalt (liftHashWithSalt2 h hashWithSalt) s m
instance Hashable1 f => Hashable1 (Free f) where
liftHashWithSalt h = go where
go s x = case x of
Pure a -> h s a
Free p -> liftHashWithSalt go s p
instance (Hashable w, Hashable1 m, Hashable a) => Hashable (WriterT w m a) where
hashWithSalt = hashWithSalt1
instance (Hashable1 f, Hashable a) => Hashable (Free f a) where
hashWithSalt = hashWithSalt1
-}
|
