Haskell JSON

SimpleJson.hs

module SimpleJson
  ( JValue(..)
  , put
  ) where

import Data.List (intercalate)

-- union type
data JValue
  = JString String
  | JNumber Float
  | JBool Bool
  | JArray [JValue]
  | JObject [(String, JValue)]
  | JNull
  deriving (Show, Eq)

-- Json to string
renderJValue :: JValue -> String
renderJValue value =
  case value of
    JString string -> show string
    JNumber number -> show number
    JBool True -> "true"
    JBool False -> "false"
    JNull -> "null"
    JArray list ->
      let values = intercalate ", " $ map renderJValue list
       in "[" ++ values ++ "]"
    JObject pairs ->
      let values =
            map (\(key, val) -> show key ++ ":" ++ renderJValue val) pairs
          keyValues = intercalate ", " values
       in "{ " ++ keyValues ++ " }"

-- print
put :: JValue -> IO ()
put = putStrLn . renderJValue

-- Run program
main :: IO ()
main = put $ JArray [JString "Peter"] -- prints: ["Peter"]