pauldraper · December 22, 2013 02:38 · Dec 22, 2013
diff --git a/BiMap.scala b/BiMap.scala
@@ -0,0 +1,50 @@
+import scala.collection.mutable.Map
+
+class BiMap[A,B] extends BiMapHelper(Map[A,B](), Map[B,A]()) {
+
+}
+
+object BiMap {
+
+   def apply[A,B](elems:(A,B)*) = new BiMap[A,B] ++= elems
+
+}
+
+/**
+ * This allows a bi-directional map to be created from any two maps.
+ * These maps must be the inverse of each other to work.
+ */
+class BiMapHelper[A,B](forward:Map[A,B], backward:Map[B,A]) extends Map[A,B] {
+
+  def inverse = new BiMapHelper(backward, forward)
+
+  def get(key:A) = forward get key
+
+  def iterator = forward.iterator
+
+  def +=(kv:(A,B)) = {
+    forward += kv
+    backward += kv.swap
+    this
+  }
+
+  def -=(key:A) = {
+    backward --= (forward get key)
+    forward -= key
+    this
+  }
+
+  override def empty = {
+    forward.empty
+    backward.empty
+    this
+  }
+
+  override def size = forward.size
+}
+
+object BiMapHelper {
+
+  def apply[A,B](forward:Map[A,B], backward:Map[B,A]) = new BiMapHelper(forward, backward)
+
+}