Scala example source code file (GenMapLike.scala)

This example Scala source code file (GenMapLike.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, boolean, c, geniterable, genmap, genmaplike, iterator, repr

The GenMapLike.scala Scala example source code

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

package scala
package collection

/** A trait for all maps upon which operations may be
 *  implemented in parallel.
 *
 *  @define Coll `GenMap`
 *  @define coll general map
 *  @author Martin Odersky
 *  @author Aleksandar Prokopec
 *  @since 2.9
 *  @define mapNote
 *
 *  A map is a collection of bindings from keys to values, where there are
 *  no duplicate keys.
 */
trait GenMapLike[A, +B, +Repr] extends GenIterableLike[(A, B), Repr] with Equals with Parallelizable[(A, B), parallel.ParMap[A, B]] {
  def default(key: A): B
  def get(key: A): Option[B]
  def apply(key: A): B
  def seq: Map[A, B]
  def +[B1 >: B](kv: (A, B1)): GenMap[A, B1]
  def - (key: A): Repr

  // This hash code must be symmetric in the contents but ought not
  // collide trivially.
  override def hashCode()= scala.util.hashing.MurmurHash3.mapHash(seq)

  /**  Returns the value associated with a key, or a default value if the key is not contained in the map.
   *   @param   key      the key.
   *   @param   default  a computation that yields a default value in case no binding for `key` is
   *                     found in the map.
   *   @tparam  B1       the result type of the default computation.
   *   @return  the value associated with `key` if it exists,
   *            otherwise the result of the `default` computation.
   *   @usecase def getOrElse(key: A, default: => B): B
   *     @inheritdoc
   */
  def getOrElse[B1 >: B](key: A, default: => B1): B1

  /** Tests whether this map contains a binding for a key.
   *
   *  @param key the key
   *  @return    `true` if there is a binding for `key` in this map, `false` otherwise.
   */
  def contains(key: A): Boolean

  /** Tests whether this map contains a binding for a key. This method,
   *  which implements an abstract method of trait `PartialFunction`,
   *  is equivalent to `contains`.
   *
   *  @param key the key
   *  @return    `true` if there is a binding for `key` in this map, `false` otherwise.
   */
  def isDefinedAt(key: A): Boolean

  def keySet: GenSet[A]

  /** Collects all keys of this map in an iterable collection.
   *
   *  @return the keys of this map as an iterable.
   */
  def keys: GenIterable[A]

  /** Collects all values of this map in an iterable collection.
   *
   *  @return the values of this map as an iterable.
   */
  def values: GenIterable[B]

  /** Creates an iterator for all keys.
   *
   *  @return an iterator over all keys.
   */
  def keysIterator: Iterator[A]

  /** Creates an iterator for all values in this map.
   *
   *  @return an iterator over all values that are associated with some key in this map.
   */
  def valuesIterator: Iterator[B]

  /** Filters this map by retaining only keys satisfying a predicate.
   *  @param  p   the predicate used to test keys
   *  @return an immutable map consisting only of those key value pairs of this map where the key satisfies
   *          the predicate `p`. The resulting map wraps the original map without copying any elements.
   */
  def filterKeys(p: A => Boolean): GenMap[A, B]

  /** Transforms this map by applying a function to every retrieved value.
   *  @param  f   the function used to transform values of this map.
   *  @return a map view which maps every key of this map
   *          to `f(this(key))`. The resulting map wraps the original map without copying any elements.
   */
  def mapValues[C](f: B => C): GenMap[A, C]

  /** Compares two maps structurally; i.e. checks if all mappings
   *  contained in this map are also contained in the other map,
   *  and vice versa.
   *
   *  @param that the other map
   *  @return     `true` if both maps contain exactly the
   *              same mappings, `false` otherwise.
   */
  override def equals(that: Any): Boolean = that match {
    case that: GenMap[b, _] =>
      (this eq that) ||
      (that canEqual this) &&
      (this.size == that.size) && {
      try {
        this forall {
          case (k, v) => that.get(k.asInstanceOf[b]) match {
            case Some(`v`) =>
              true
            case _ => false
          }
        }
      } catch {
        case ex: ClassCastException =>
          println("class cast "); false
      }}
    case _ =>
      false
  }
}