Scala example source code file (DefaultMap.scala)

This example Scala source code file (DefaultMap.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

a, b, b1, defaultmap, map

The DefaultMap.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection

/** A default map which implements the `+` and `-` methods of maps.
 *
 *  Instances that inherit from `DefaultMap[A, B]` still have to define:
 *  {{{
 *    def get(key: A): Option[B]
 *    def iterator: Iterator[(A, B)]
 *  }}}
 *  It refers back to the original map.
 *
 *  It might also be advisable to override `foreach` or `size` if efficient
 *  implementations can be found.
 *
 *  @since 2.8
 */
trait DefaultMap[A, +B] extends Map[A, B] { self =>

  /** A default implementation which creates a new immutable map.
   */
  override def +[B1 >: B](kv: (A, B1)): Map[A, B1] = {
    val b = Map.newBuilder[A, B1]
    b ++= this
    b += ((kv._1, kv._2))
    b.result()
  }

  /** A default implementation which creates a new immutable map.
   */
  override def - (key: A): Map[A, B] = {
    val b = newBuilder
    b ++= this filter (key != _._1)
    b.result()
  }
}