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diff --git a/src/library/scalax/collection/generic/Subtractable.scala b/src/library/scalax/collection/generic/Subtractable.scala
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+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2003-2009, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+// $Id: Iterable.scala 15188 2008-05-24 15:01:02Z stepancheg $
+
+package scalax.collection.generic
+
+/** This class represents collections that can be reduced using a -= operator.
+ *
+ *  @autor   Martin Odersky
+ *  @owner   Martin Odersky
+ *  @version 2.8
+ */
+trait Subtractable[+C <: Subtractable[C, A], A] {
+
+  protected def thisCC: C
+
+  /** Removes a single element from this collection and returns
+   *  either the collection itself (if it is mutable), or a new collection
+   *  with the removed element.
+   *
+   *  @param elem  the element to remove.
+   */
+  def -(elem: A): C
+
+  /** Removes two or more elements from this collection and returns
+   *  either the collection itself (if it is mutable), or a new collection
+   *  with the removed elements.
+   *
+   *  @param elem1 the first element to remove.
+   *  @param elem2 the second element to remove.
+   *  @param elems the remaining elements to remove.
+   */
+  def -(elem1: A, elem2: A, elems: A*): C =
+    thisCC - elem1 - elem2 -- elems.asInstanceOf[Iterable[A]] // !@!
+
+  /** Removes a number of elements provided by an iterable object
+   *  via its <code>elements</code> method and returns
+   *  either the collection itself (if it is mutable), or a new collection
+   *  with the removed elements.
+   *
+   *  @param iter     the iterable object.
+   */
+  def --(iter: Iterable[A]): C = (thisCC /: iter) (_ - _)
+
+  /** Removes a number of elements provided by an iterator
+   *  via its <code>elements</code> method and returns
+   *  either the collection itself (if it is mutable), or a new collection
+   *  with the removed elements.
+   *
+   *  @param iter   the iterator
+   */
+  def --(iter: Iterator[A]): C = (thisCC /: iter) (_ - _)
+
+}
+
+
+
+