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diff --git a/src/library/scala/collection/immutable/Queue.scala b/src/library/scala/collection/immutable/Queue.scala
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+++ b/src/library/scala/collection/immutable/Queue.scala
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+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003-2005, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+** $Id$
+\*                                                                      */
+
+package scala.collection.immutable;
+
+
+object Queue {
+  val Empty: Queue[All] = new Queue();
+}
+
+/** <code>Queue</code> objects implement data structures that allow to
+ *  insert and retrieve elements in a first-in-first-out (FIFO) manner.
+ *
+ *  @author  Erik Stenman
+ *  @version 1.0, 08/07/2003
+ */
+[serializable]
+class Queue[+A](elem: A*) extends Seq[A] {
+  protected val in: List[A] = Nil;
+  protected val out: List[A] = itToList(elem.elements);
+
+  protected def itToList[B >: A](elems: Iterator[B]): List[B] =
+    if (elems.hasNext) {
+      val hd = elems.next;
+      hd :: itToList(elems)
+    }
+    else
+      Nil;
+
+  protected def mkQueue[A](i: List[A], o: List[A]): Queue[A] =
+    new Queue[A]() {
+      override protected val in = i;
+      override protected val out = o
+    };
+
+  /** Returns the <code>n</code>-th element of this queue.
+   *  The first element is at position 0.
+   *
+   *  @param n index of the element to return
+   *  @return the element at position <code>n</code> in this list.
+   *  @throws java.lang.RuntimeException if the list is too short.
+   */
+  def apply(n: Int): A =
+    if (n < out.length) out.apply(n)
+    else in.reverse.apply(n - out.length);
+
+  /** Returns the elements in the list as an iterator
+   */
+  def elements: Iterator[A] = (out ::: in.reverse).elements;
+
+  /** Checks if the queue is empty.
+   *
+   *  @return true, iff there is no element in the queue.
+   */
+  def isEmpty: Boolean = in.isEmpty && out.isEmpty;
+
+  /** Returns the length of the queue.
+   */
+  def length = in.length + out.length;
+
+  /** Creates a new queue with element added at the end
+   *  of the old queue.
+   *
+   *  @param  elem        the element to insert
+   */
+  def +[B >: A](elem: B) = mkQueue(elem :: in, out);
+
+  /** Returns a new queue with all all elements provided by
+   *  an <code>Iterable</code> object added at the end of
+   *  the queue.
+   *  The elements are prepended in the order they
+   *  are given out by the iterator.
+   *
+   *  @param  iter        an iterable object
+   */
+  def +[B >: A](iter: Iterable[B]) = {
+    var q: List[B] = in;
+    iter.elements.foreach(e => q = e :: q);
+    mkQueue(q, out);
+  }
+
+  /** Returns a new queue with all elements added.
+   *
+   *  @param  elems       the elements to add.
+   */
+  def enqueue [B >: A](elems: B*) = this + elems;
+
+  /** Returns a tuple with the first element in the queue,
+   *  and a new queue with this element removed.
+   *
+   *  @return the first element of the queue.
+   */
+  def dequeue: Pair[A, Queue[A]] = {
+    val Pair(newOut, newIn) =
+      if (out.isEmpty) Pair(in.reverse, Nil)
+      else Pair(out, in);
+    if (newOut.isEmpty) error("queue empty");
+    else Pair(newOut.head, mkQueue(newIn, newOut.tail));
+  }
+
+  /** Returns the first element in the queue, or throws an error if there
+   *  is no element contained in the queue.
+   *
+   *  @return the first element.
+   */
+  def front: A =
+    if (out.isEmpty) {
+      if (in.isEmpty) error("queue empty") else in.last;
+    } else
+      out.head;
+
+  /** Returns a string representation of this queue. The resulting string
+   *  begins with the string <code>start</code> and is finished by the string
+   *    <code>end</code>. Inside, the string representations of elements (w.r.t.
+   *  the method <code>toString()</code>) are separated by the string
+   *  <code>sep</code>.
+   *  <p/>
+   *  Ex: <br/>
+   *  <code>Queue(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"</code>
+   *
+   *  @param start starting string.
+   *  @param sep separator string.
+   *  @param end ending string.
+   *  @return a string representation of this list.
+   */
+  def mkString(start: String, sep: String, end: String): String =
+    (out ::: in.reverse).mkString(start, sep, end);
+
+  /** Returns a string representation of this queue.
+   */
+  override def toString() = (out ::: in.reverse).mkString("Queue(", ",", ")");
+
+  /** Compares two queues for equality by comparing
+   *  each element in the queues.
+   *
+   *  @return true, iff the two queues are structurally equal.
+   */
+  override def equals(o: Any): Boolean = o match {
+    case q: Queue[Any] =>
+      /* A function that compares the element at
+         position index in q with the element at
+         the same position in this (queue).
+         If they are equal the next element is
+         compared. */
+      def eqe(index: Int): Boolean = (
+        /* If all elements are compared
+        the queues are equal. */
+        index >= this.length ||
+        /* Otherwise: compare the elements */
+        (q.apply(index) == this.apply(index) &&
+         /* if they are equal compare the rest. */
+         eqe(index + 1))
+      );
+        /* If the length of the ques are the same,
+         compare each element, starting at index 0. */
+      (q.length == this.length) && eqe(0);
+
+    case _ => false; /* o is not a queue: not equal to this. */
+  }
+
+  override def hashCode(): Int =
+    if (isEmpty) 0
+    else {
+      val q: Pair[A,Queue[A]] = dequeue;
+      q._1.hashCode() + q._2.hashCode();
+    }
+}