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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2011, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
package generic
/** This trait represents collection-like objects that can be reduced
* using a '+' operator. It defines variants of `-` and `--`
* as convenience methods in terms of single-element removal `-`.
* @tparam A the type of the elements of the $coll.
* @tparam Repr the type of the $coll itself
* @author Martin Odersky
* @version 2.8
* @since 2.8
* @define coll collection
* @define Coll Subtractable
*/
trait Subtractable[A, +Repr <: Subtractable[A, Repr]] { self =>
/** The representation object of type `Repr` which contains the collection's elements
*/
protected def repr: Repr
/** Creates a new $coll from this $coll with an element removed.
* @param elem the element to remove
* @return a new collection that contains all elements of the current $coll
* except one less occurrence of `elem`.
*/
def -(elem: A): Repr
/** Creates a new $coll from this $coll with some elements removed.
*
* This method takes two or more elements to be removed. Another overloaded
* variant of this method handles the case where a single element is
* removed.
* @param elem1 the first element to remove.
* @param elem2 the second element to remove.
* @param elems the remaining elements to remove.
* @return a new $coll that contains all elements of the current $coll
* except one less occurrence of each of the given elements.
*/
def -(elem1: A, elem2: A, elems: A*): Repr =
this - elem1 - elem2 -- elems
/** Creates a new $coll from this $coll by removing all elements of another
* collection.
*
* @param xs the collection containing the removed elements.
* @return a new $coll that contains all elements of the current $coll
* except one less occurrence of each of the elements of `elems`.
*/
def --(xs: GenTraversableOnce[A]): Repr = (repr /: xs.seq) (_ - _)
}
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