argonaut_read.scala

//reads input string, checks if its json, and if it is returns an encoded object of the first type that parses correctly.
def read[A](input: String)(implicit decoder: DecodeJson[A]): Option[A] = { // require that the decodeJson for type A be in scope
  JsonParser.parse(input).toOption match {
    case None => {
      throw new AlgorithmException(s"input failed to parse.")
    }
    case Some(json: Json) => {
      val decoded = decoder.decodeJson(json).toOption
      decoded
    }
  }
}