Scala example source code file (Map.scala)

This example Scala source code file (Map.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, abstractmap, b, b1, canbuildfrom, iterable, map, maplike, mutablemapfactory, withdefault

The Map.scala Scala example source code

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



package scala
package collection
package mutable

import generic._

/** A base trait for maps that can be mutated.
 *  $mapNote
 *  $mapTags
 *  @since 1.0
 *  @author  Matthias Zenger
 */
trait Map[A, B]
  extends Iterable[(A, B)]
//     with GenMap[A, B]
     with scala.collection.Map[A, B]
     with MapLike[A, B, Map[A, B]] {

  override def empty: Map[A, B] = Map.empty

  override def seq: Map[A, B] = this

  /** The same map with a given default function.
   *
   *  Invoking transformer methods (e.g. `map`) will not preserve the default value.
   *
   *  @param d     the function mapping keys to values, used for non-present keys
   *  @return      a wrapper of the map with a default value
   */
  def withDefault(d: A => B): mutable.Map[A, B] = new Map.WithDefault[A, B](this, d)

  /** The same map with a given default value.
   *
   *  Invoking transformer methods (e.g. `map`) will not preserve the default value.
   *
   *  @param d     default value used for non-present keys
   *  @return      a wrapper of the map with a default value
   */
  def withDefaultValue(d: B): mutable.Map[A, B] = new Map.WithDefault[A, B](this, x => d)
}

/** $factoryInfo
 *  The current default implementation of a $Coll is a `HashMap`.
 *  @define coll mutable map
 *  @define Coll `mutable.Map`
 */
object Map extends MutableMapFactory[Map] {
  /** $canBuildFromInfo */
  implicit def canBuildFrom[A, B]: CanBuildFrom[Coll, (A, B), Map[A, B]] = new MapCanBuildFrom[A, B]

  def empty[A, B]: Map[A, B] = new HashMap[A, B]

  class WithDefault[A, B](underlying: Map[A, B], d: A => B) extends scala.collection.Map.WithDefault(underlying, d) with Map[A, B] {
    override def += (kv: (A, B)) = {underlying += kv; this}
    def -= (key: A) = {underlying -= key; this}
    override def empty = new WithDefault(underlying.empty, d)
    override def updated[B1 >: B](key: A, value: B1): WithDefault[A, B1] = new WithDefault[A, B1](underlying.updated[B1](key, value), d)
    override def + [B1 >: B](kv: (A, B1)): WithDefault[A, B1] = updated(kv._1, kv._2)
    override def - (key: A): WithDefault[A, B] = new WithDefault(underlying - key, d)

    /** If these methods aren't overridden to thread through the underlying map,
     *  successive calls to withDefault* have no effect.
     */
    override def withDefault(d: A => B): mutable.Map[A, B] = new WithDefault[A, B](underlying, d)
    override def withDefaultValue(d: B): mutable.Map[A, B] = new WithDefault[A, B](underlying, x => d)
  }
}

/** Explicit instantiation of the `Map` trait to reduce class file size in subclasses. */
abstract class AbstractMap[A, B] extends scala.collection.AbstractMap[A, B] with Map[A, B]