JSON data model in Haskell (mostly from scratch) with a compact printing function

Json.hs

{-# LANGUAGE OverloadedStrings #-}
module Json (
  Value,
  -- core API
  true, false, nil, number, text, array, object,
  -- utils and demo
  objects, (.:), jprint, run
) where

import Data.Monoid
-- need a few non-std imports for efficiency
-- e.g.: Never use String in Haskell
import Data.Text (Text, unpack, pack, intercalate)
import Data.Map.Strict (Map, foldlWithKey', empty, insert, toList)

-- core data type
data Value
  = Null
  | JBool Bool
  | JNumber Double
  | JString Text
  | JArray [Value]
  | JObject Object

-- convenience wrapper
newtype Object = Object (Map Text Value)

-- convenience functions
array = JArray
true = JBool True
false = JBool False
number = JNumber
text = JString
nil = Null
object = JObject

objects :: Object
objects = Object empty

infixl 5 .:
(.:) :: Object -> (Text,Value) -> Object
(Object o) .: (k,v) = Object (insert k v o)

jprint :: Value -> Text
jprint val =
  case val of
    Null -> "null"
    (JBool x) -> if x then "true" else "false"
    (JNumber x) -> pack (show x)
    (JString x) -> x
    (JArray xs) -> "[" <> intercalate "," (map jprint xs) <> "]"
    (JObject o) -> "{" <> pprintMap o <> "}"
  where pprintMap (Object m) =
          intercalate "," (map (\(k,v) -> k <> ":" <> jprint v) $ toList m)

run :: IO ()
run =
  let objs = object (objects .: ("foo", text "FOO") .: ("bar", text "BAR"))
      val = JArray [objs, number 3, nil, true, false]
  in print (jprint val)

Uses this json.cabal file:

-- Initial json.cabal generated by cabal init.  For further documentation, 
-- see http://haskell.org/cabal/users-guide/

name:                json
version:             0.1.0.0
synopsis:            Json
-- description:         
license:             GPL-3
license-file:        LICENSE
author:              Allele Dev
maintainer:          allele.dev@gmail.com
-- copyright:           
category:            Data
build-type:          Simple
-- extra-source-files:  
cabal-version:       >=1.10

library
  exposed-modules:     Json
  -- other-modules:       
  other-extensions:    OverloadedStrings
  build-depends:       base >=4.8 && <4.9, containers >=0.5 && <0.6, text
  hs-source-dirs:      src
  default-language:    Haskell2010