Is there such a thing as bidirectional maps in Scala?

Question

I\'d like to link 2 columns of unique identifiers and be able to get a first column value by a second column value as well as a second column value by a first column value. Some

Answer 1

Guava has a bimap that you can use along with

import scala.collection.JavaConversions._

Answer 2

My BiMap approach:

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

case class BiMap[X, Y](map: Map[X, Y]) {
  def this(tuples: (X,Y)*) = this(tuples.toMap)
  private val reverseMap = map map (_.swap)
  require(map.size == reverseMap.size, "no 1 to 1 relation")
  def apply(x: X): Y = map(x)
  def apply(y: Y)(implicit d: BiMap.MethodDistinctor): X = reverseMap(y)
  val domain = map.keys
  val codomain = reverseMap.keys
}

val biMap = new BiMap(1 -> "A", 2 -> "B")
println(biMap(1)) // A
println(biMap("B")) // 2

Of course one can add syntax for <-> instead of ->.