Scala example source code file (GenSetLike.scala)

This example Scala source code file (GenSetLike.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, boolean, classcastexception, equals, geniterablelike, genset, gensetlike, iterator, parallelizable, repr

The GenSetLike.scala Scala example source code

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

package scala
package collection


/** A template trait for sets which may possibly
 *  have their operations implemented in parallel.
 *
 *  @define Coll GenSet
 *  @define coll general set
 *  @author Martin Odersky
 *  @author Aleksandar Prokopec
 *  @since 2.9
 *  @define setNote
 *
 *  A set is a collection that contains no duplicate elements.
 */
trait GenSetLike[A, +Repr]
extends GenIterableLike[A, Repr]
   with (A => Boolean)
   with Equals
   with Parallelizable[A, parallel.ParSet[A]] {

  def iterator: Iterator[A]
  def contains(elem: A): Boolean
  def +(elem: A): Repr
  def -(elem: A): Repr

  def seq: Set[A]

  /** Tests if some element is contained in this set.
   *
   *  This method is equivalent to `contains`. It allows sets to be interpreted as predicates.
   *  @param elem the element to test for membership.
   *  @return  `true` if `elem` is contained in this set, `false` otherwise.
   */
  def apply(elem: A): Boolean = this contains elem

  /** Computes the intersection between this set and another set.
   *
   *  @param   that  the set to intersect with.
   *  @return  a new set consisting of all elements that are both in this
   *  set and in the given set `that`.
   */
  def intersect(that: GenSet[A]): Repr = this filter that

  /** Computes the intersection between this set and another set.
   *
   *  '''Note:'''  Same as `intersect`.
   *  @param   that  the set to intersect with.
   *  @return  a new set consisting of all elements that are both in this
   *  set and in the given set `that`.
   */
  def &(that: GenSet[A]): Repr = this intersect that

  /** Computes the union between of set and another set.
   *
   *  @param   that  the set to form the union with.
   *  @return  a new set consisting of all elements that are in this
   *  set or in the given set `that`.
   */
  def union(that: GenSet[A]): Repr

  /** Computes the union between this set and another set.
   *
   *  '''Note:'''  Same as `union`.
   *  @param   that  the set to form the union with.
   *  @return  a new set consisting of all elements that are in this
   *  set or in the given set `that`.
   */
  def | (that: GenSet[A]): Repr = this union that

  /** Computes the difference of this set and another set.
   *
   *  @param that the set of elements to exclude.
   *  @return     a set containing those elements of this
   *              set that are not also contained in the given set `that`.
   */
  def diff(that: GenSet[A]): Repr

  /** The difference of this set and another set.
   *
   *  '''Note:'''  Same as `diff`.
   *  @param that the set of elements to exclude.
   *  @return     a set containing those elements of this
   *              set that are not also contained in the given set `that`.
   */
  def &~(that: GenSet[A]): Repr = this diff that

  /** Tests whether this set is a subset of another set.
   *
   *  @param that  the set to test.
   *  @return     `true` if this set is a subset of `that`, i.e. if
   *              every element of this set is also an element of `that`.
   */
  def subsetOf(that: GenSet[A]): Boolean = this forall that

  /** Compares this set with another object for equality.
   *
   *  '''Note:''' This operation contains an unchecked cast: if `that`
   *        is a set, it will assume with an unchecked cast
   *        that it has the same element type as this set.
   *        Any subsequent ClassCastException is treated as a `false` result.
   *  @param that the other object
   *  @return     `true` if `that` is a set which contains the same elements
   *              as this set.
   */
  override def equals(that: Any): Boolean = that match {
    case that: GenSet[_] =>
      (this eq that) ||
      (that canEqual this) &&
      (this.size == that.size) &&
      (try this subsetOf that.asInstanceOf[GenSet[A]]
       catch { case ex: ClassCastException => false })
    case _ =>
      false
  }

  // Careful! Don't write a Set's hashCode like:
  //    override def hashCode() = this map (_.hashCode) sum
  // Calling map on a set drops duplicates: any hashcode collisions would
  // then be dropped before they can be added.
  // Hash should be symmetric in set entries, but without trivial collisions.
  override def hashCode()= scala.util.hashing.MurmurHash3.setHash(seq)
}