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|
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2010, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection
import generic._
import mutable.{Builder, AddingBuilder}
import PartialFunction._
/** A template trait for sets of type `Set[A]`.
*
* This trait provides most of the operations of a `Set` independently of its representation.
* It is typically inherited by concrete implementations of sets.
*
* $setnote
*
* @tparam A the type of the elements of the set
* @tparam This the type of the set itself.
*
* @author Martin Odersky
* @version 2.8
* @define setnote
* To implement a concrete set, you need to provide implementations of the
* following methods:
* {{{
* def contains(key: A): Boolean
* def iterator: Iterator[A]
* def +(elem: A): This
* def -(elem: A): This
* }}}
* If you wish that methods like `take`, `drop`,
* `filter` return the same kind of set, you should also override:
* {{{
* def empty: This
* }}}
* It is also good idea to override methods `foreach` and
* `size` for efficiency.
* @define coll set
* @define Coll Set
* @define willNotTerminateInf
* @define mayNotTerminateInf
*/
trait SetLike[A, +This <: SetLike[A, This] with Set[A]]
extends IterableLike[A, This]
with Addable[A, This]
with Subtractable[A, This] {
self =>
/* The empty set of the same type as this set
* @return an empty set of type `This`.
*/
def empty: This
/** A common implementation of `newBuilder` for all sets in terms
* of `empty`. Overridden for mutable sets in
* <a href="mutable/SetLike.html" target="ContentFrame">
* `mutable.SetLike`</a>.
*/
override protected[this] def newBuilder: Builder[A, This] = new AddingBuilder[A, This](empty)
/** Tests if some element is contained in this set.
*
* @param elem the element to test for membership.
* @return `true` if `elem` is contained in this set, `false` otherwise.
*/
def contains(elem: A): Boolean
/** Creates a new set with an additional element, unless the element is
* already present.
*
* @param elem the element to be added
* @return a new set that contains all elements of this set and that also
* contains `elem`.
*/
def + (elem: A): This
/** Creates a new set with a given element removed from this set.
*
* @param elem the element to be removed
* @return a new set that contains all elements of this set but that does not
* contain `elem`.
*/
def - (elem: A): This
/** Tests if this set is empty.
*
* @return `true` if there is no element in the set, `false` otherwise.
*/
override def isEmpty: Boolean = size == 0
/** 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 = 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: Set[A]): This = filter(that.contains)
/** 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`.
* @note Same as `intersect`.
*/
def &(that: Set[A]): This = intersect(that)
/** This method is an alias for `intersect`.
* It computes an intersection with set `that`.
* It removes all the elements that are not present in `that`.
*
* @param that the set to intersect with
*/
@deprecated("use & instead") def ** (that: Set[A]): 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: Set[A]): This = this.++(that)
/** Computes the union between this 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`.
* @note Same as `union`.
*/
def | (that: Set[A]): 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: Set[A]): This = --(that)
/** 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`.
* @note Same as `diff`.
*/
def &~(that: Set[A]): 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: Set[A]): Boolean = forall(that.contains)
/** Defines the prefix of this object's `toString` representation.
* @return a string representation which starts the result of `toString` applied to this set.
* Unless overridden this is simply `"Set"`.
*/
override def stringPrefix: String = "Set"
override def toString = super[IterableLike].toString
override def hashCode() = this map (_.hashCode) sum
/** Compares this set with another object for equality.
*
* @param that the other object
* @return `true` if `that` is a set which contains the same elements
* as this set.
* @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 subsequuent ClassCastException is treated as a `false` result.
*/
override def equals(that: Any): Boolean = that match {
case that: Set[_] =>
(this eq that) ||
(that canEqual this) &&
(this.size == that.size) &&
(try this subsetOf that.asInstanceOf[Set[A]]
catch { case ex: ClassCastException => false })
case _ =>
false
}
}
|
