Hasell show typeclass

HaskellShowTypeClass.hs

import Data.Text

data MyCaseClass
  = MyCaseClass
  { _id :: Int
  , name :: Text
  }

data MyOtherCaseClass
  = MyOtherCaseClass
  { __id :: Int
  , _name :: Text
  }


class MyShow a where
  myShow :: a -> String

instance MyShow Int where
  myShow x = "int " ++ show x

instance MyShow Text where
  myShow x = "a string " ++ show x

instance MyShow a => MyShow (Maybe a) where
  myShow x =
    case x of
      Just y  -> "Some " ++ myShow y
      Nothing -> "Nothing"

instance (MyShow a, MyShow b) => MyShow (Either a b) where
  myShow x =
    case x of
      Left  l -> "left " ++ myShow l
      Right r -> "right " ++ myShow r

instance MyShow MyCaseClass where
  myShow (MyCaseClass _id name) =
    myShow _id ++ " " ++ myShow name

main = do
  putStrLn $ myShow $ (233 :: Int)
  putStrLn $ myShow $ pack "Hello"
  putStrLn $ myShow $ Just (223 :: Int)
  putStrLn $ myShow $ Just $ pack "hello"
  putStrLn $ myShow $ (Right (83 :: Int) :: Either Int Int)
  putStrLn $ myShow $ MyCaseClass { _id = 1, name = (pack "eric") }