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/*
 * Scala (https://www.scala-lang.org)
 *
 * Copyright EPFL and Lightbend, Inc.
 *
 * Licensed under Apache License 2.0
 * (http://www.apache.org/licenses/LICENSE-2.0).
 *
 * See the NOTICE file distributed with this work for
 * additional information regarding copyright ownership.
 */

package scala
package collection

import generic._

/**
 *  A map from keys of type `K` to values of type `V`.
 *
 *  $mapNote
 *
 *  '''Note:''' If you do not have specific implementations for `add` and `-` in mind,
 *        you might consider inheriting from `DefaultMap` instead.
 *
 *  '''Note:''' If your additions and mutations return the same kind of map as the map
 *        you are defining, you should inherit from `MapLike` as well.
 *
 *  @tparam K     the type of the keys in this map.
 *  @tparam V     the type of the values associated with keys.
 *
 *  @since 1.0
 */
trait Map[K, +V] extends Iterable[(K, V)] with GenMap[K, V] with MapLike[K, V, Map[K, V]] {
  def empty: Map[K, V] = Map.empty

  override def seq: Map[K, V] = this
}

/** $factoryInfo
 *  @define Coll `Map`
 *  @define coll map
 */
object Map extends MapFactory[Map] {
  def empty[K, V]: immutable.Map[K, V] = immutable.Map.empty

  /** $mapCanBuildFromInfo */
  implicit def canBuildFrom[K, V]: CanBuildFrom[Coll, (K, V), Map[K, V]] =
    ReusableCBF.asInstanceOf[CanBuildFrom[Coll, (K, V), Map[K, V]]]
  private[this] val ReusableCBF = new MapCanBuildFrom[Nothing, Nothing]

  /** An abstract shell used by { mutable, immutable }.Map but not by collection.Map
   *  because of variance issues.
   */
  abstract class WithDefault[K, +V](underlying: Map[K, V], d: K => V) extends AbstractMap[K, V] with Map[K, V] with Serializable {
    override def size               = underlying.size
    def get(key: K)                 = underlying.get(key) // removed in 2.9: orElse Some(default(key))
    def iterator                    = underlying.iterator
    override def default(key: K): V = d(key)
  }

}

/** Explicit instantiation of the `Map` trait to reduce class file size in subclasses. */
abstract class AbstractMap[K, +V] extends AbstractIterable[(K, V)] with Map[K, V]