module Main where

data User = User String Integer
  deriving (Eq, Show)

class ToJson a where
  toJson :: a -> String

instance ToJson User where
  toJson (User name phone) =
    "{\"name\"" ++ name ++ "\", \"phone\":" ++ show phone ++ "}"

main :: IO ()
main = putStrLn . toJson $ User "Rob" 3452341234