taming Either

taming_either.scala

class RichEither[L, R](val either: Either[L, R]) {
  def mapRight[RR](f: R => RR): Either[L, RR] = either match {
    case Left(l) => Left(l)
    case Right(r) => Right(f(r))
  }
}

implicit def either2rich[L, R](either: Either[L, R]) = new RichEither(either)

/*
 def readFile(name: File): Either[String, String] = { ... }

 def parseJson(raw: String): Either[String, JObject] = { ... }

 def parsePerson(json: JObject): Either[String, Person] = { ... }
 
 readFile("foo.json").mapRight(parseJson).mapRight(parsePerson)
 */