Purely functional JSON in Scala

Example Argonaut JSON Scala code:

package argonaut.doc
import scalaz._, Scalaz._
import argonaut._, Argonaut._
object QuickStartExample extends App {
val input = """
{ "name": "Mark", "age": 191 },
{ "name": "Fred", "age": 33, "greeting": "hey ho, lets go!" },
{ "name": "Barney", "age": 35, "address": {
"street": "rock street", "number": 10, "post_code": 2039
// parse the string as json, attempt to decode it to a list of person,
// otherwise just take it as an empty list.
val people = input.decodeOption[List[Person]].getOrElse(Nil)
// work with your data types as you normally would
val nice = people.map(person =>
person.copy(greeting = person.greeting.orElse(Some("Hello good sir!"))))
// convert back to json, and then to a pretty printed string, alternative
// ways to print may be nospaces, spaces2, or a custom format
val result = nice.asJson
assert(result.array.exists(_.length == 3))
case class Address(street: String, number: Int, postcode: Int)
object Address {
// Define codecs easily from case classes
implicit def AddressCodecJson: CodecJson[Address] =
casecodec3(Address.apply, Address.unapply)("street", "number", "post_code")
case class Person(name: String, age: Int, address: Option[Address], greeting: Option[String])
object Person {
implicit def AddressCodecJson: CodecJson[Person] =
casecodec4(Person.apply, Person.unapply)("name", "age", "address", "greeting")