如何使用Haskell将数据编码为JSON？

{-# LANGUAGE DeriveGeneric #-}

import Data.Aeson
import GHC.Generics

-- 定义自定义数据类型
data Person = Person
  { name :: String
  , age :: Int
  } deriving (Show, Generic)

-- 实现ToJSON实例
instance ToJSON Person

-- 将数据编码为JSON
encodePerson :: Person -> Maybe ByteString
encodePerson = encode . toJSON

-- 示例数据
person :: Person
person = Person "John Doe" 30

main :: IO ()
main = do
  let json = encodePerson person
  case json of
    Just jsonString -> putStrLn $ "JSON: " ++ unpack jsonString
    Nothing -> putStrLn "Failed to encode JSON"