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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection
package immutable
import generic._
/** <p>
* A generic trait for immutable sets. Concrete set implementations have
* to provide functionality for the abstract methods in <code>Set</code>:
* </p>
* <pre>
* <b>def</b> contains(elem: A): Boolean
* <b>def</b> iterator: Iterator[A]
* <b>def</b> + (elem: A): This
* <b>def</b> - (elem: A): This</pre>
* <p>
* where <code>This</code> is the type of the set.
* </p>
*
* @author Matthias Zenger
* @author Martin Odersky
* @version 2.8
* @since 1
*/
trait Set[A] extends Iterable[A]
with scala.collection.Set[A]
with GenericSetTemplate[A, Set]
with SetLike[A, Set[A]] {
override def companion: GenericCompanion[Set] = Set
}
object Set extends SetFactory[Set] {
implicit def builderFactory[A]: BuilderFactory[A, Set[A], Coll] = setBuilderFactory[A]
override def empty[A]: Set[A] = new EmptySet[A]
private val hashSeed = "Set".hashCode
/** An optimized representation for immutable empty sets */
@serializable
class EmptySet[A] extends Set[A] {
override def size: Int = 0
def contains(elem: A): Boolean = false
def + (elem: A): Set[A] = new Set1(elem)
def - (elem: A): Set[A] = this
def iterator: Iterator[A] = Iterator.empty
override def foreach[U](f: A => U): Unit = {}
}
/** An optimized representation for immutable sets of size 1 */
@serializable
class Set1[A](elem1: A) extends Set[A] {
override def size: Int = 1
def contains(elem: A): Boolean =
elem == elem1
def + (elem: A): Set[A] =
if (contains(elem)) this
else new Set2(elem1, elem)
def - (elem: A): Set[A] =
if (elem == elem1) new EmptySet[A]
else this
def iterator: Iterator[A] =
Iterator(elem1)
override def foreach[U](f: A => U): Unit = {
f(elem1)
}
}
/** An optimized representation for immutable sets of size 2 */
@serializable
class Set2[A](elem1: A, elem2: A) extends Set[A] {
override def size: Int = 2
def contains(elem: A): Boolean =
elem == elem1 || elem == elem2
def + (elem: A): Set[A] =
if (contains(elem)) this
else new Set3(elem1, elem2, elem)
def - (elem: A): Set[A] =
if (elem == elem1) new Set1(elem2)
else if (elem == elem2) new Set1(elem1)
else this
def iterator: Iterator[A] =
Iterator(elem1, elem2)
override def foreach[U](f: A => U): Unit = {
f(elem1); f(elem2)
}
}
/** An optimized representation for immutable sets of size 3 */
@serializable
class Set3[A](elem1: A, elem2: A, elem3: A) extends Set[A] {
override def size: Int = 3
def contains(elem: A): Boolean =
elem == elem1 || elem == elem2 || elem == elem3
def + (elem: A): Set[A] =
if (contains(elem)) this
else new Set4(elem1, elem2, elem3, elem)
def - (elem: A): Set[A] =
if (elem == elem1) new Set2(elem2, elem3)
else if (elem == elem2) new Set2(elem1, elem3)
else if (elem == elem3) new Set2(elem1, elem2)
else this
def iterator: Iterator[A] =
Iterator(elem1, elem2, elem3)
override def foreach[U](f: A => U): Unit = {
f(elem1); f(elem2); f(elem3)
}
}
/** An optimized representation for immutable sets of size 4 */
@serializable
class Set4[A](elem1: A, elem2: A, elem3: A, elem4: A) extends Set[A] {
override def size: Int = 4
def contains(elem: A): Boolean =
elem == elem1 || elem == elem2 || elem == elem3 || elem == elem4
def + (elem: A): Set[A] =
if (contains(elem)) this
else new HashSet[A] + (elem1, elem2, elem3, elem4, elem)
def - (elem: A): Set[A] =
if (elem == elem1) new Set3(elem2, elem3, elem4)
else if (elem == elem2) new Set3(elem1, elem3, elem4)
else if (elem == elem3) new Set3(elem1, elem2, elem4)
else if (elem == elem4) new Set3(elem1, elem2, elem3)
else this
def iterator: Iterator[A] =
Iterator(elem1, elem2, elem3, elem4)
override def foreach[U](f: A => U): Unit = {
f(elem1); f(elem2); f(elem3); f(elem4)
}
}
}
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