Serialization of Double.NaN

gistfile1.scala

// sample class with a double value
case class DoubleNanTest(price: Double)

// define typeclass instance for serialization
import dispatch.json._
implicit val DoubleNanTestFormat: Format[DoubleNanTest] = new Format[DoubleNanTest] {
  def reads(json: JsValue): DoubleNanTest = json match {
    case JsString("Double.NaN") => DoubleNanTest(scala.Double.NaN) // special treatment for NaN
    case JsNumber(n) => DoubleNanTest(n.doubleValue)
    case _ => error("Invalid DoubleNanTest")
  }
  def writes(a: DoubleNanTest): JsValue = a.price match {
    case x if x equals scala.Double.NaN => JsString("Double.NaN") // special treatment for NaN
    case x => JsNumber(BigDecimal.valueOf(x))
  }
}

// test script for serialization
describe("Serialization of double NaN") {
  it ("should serialize") {
    val x = DoubleNanTest(scala.Double.NaN)
    x.price.isNaN should equal(true)
    fromjson[DoubleNanTest](tojson(x)).price.isNaN should equal(true)
  }
}