BiMap.scala

// Similar to http://stackoverflow.com/questions/9850786/is-there-such-a-thing-as-bidirectional-maps-in-scala#9851520

object BiMap {
  private[BiMap] trait MethodDistinctor
  implicit final object MethodDistinctor extends MethodDistinctor

  def apply[X, Y](tuples: (X, Y)*) = new BiMap(tuples.toMap, tuples.map(_.swap).toMap)
  def apply[X, Y](m: Map[X, Y]) = new BiMap(m, m.toSeq.map(_.swap).toMap)

}

class BiMap[X, Y](m1: Map[X, Y], m2: Map[Y, X]) {
  def apply(x: X): Y = m1(x)
  def apply(y: Y)(implicit d: BiMap.MethodDistinctor): X = m2(y)
}