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Standard library for the Scala Programming Language
/*
* 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
package immutable
import generic._
import parallel.immutable.ParSet
/** A generic trait for immutable sets.
* $setNote
* $setTags
*
* @since 1.0
* @author Matthias Zenger
* @author Martin Odersky
* @define Coll `immutable.Set`
* @define coll immutable set
*/
trait Set[A] extends Iterable[A]
// with GenSet[A]
with scala.collection.Set[A]
with GenericSetTemplate[A, Set]
with SetLike[A, Set[A]]
with Parallelizable[A, ParSet[A]]
{
override def companion: GenericCompanion[Set] = Set
/** Returns this $coll as an immutable set, perhaps accepting a
* wider range of elements. Since it already is an
* immutable set, it will only be rebuilt if the underlying structure
* cannot be expanded to include arbitrary element types.
* For instance, `BitSet` and `SortedSet` will be rebuilt, as
* they require `Int` and sortable elements respectively.
*
* When in doubt, the set will be rebuilt. Rebuilt sets never
* need to be rebuilt again.
*/
override def toSet[B >: A]: Set[B] = {
// This way of building sets typically has the best benchmarks, surprisingly!
val sb = Set.newBuilder[B]
foreach(sb += _)
sb.result()
}
override def seq: Set[A] = this
protected override def parCombiner = ParSet.newCombiner[A] // if `immutable.SetLike` gets introduced, please move this there!
}
/** $factoryInfo
* @define Coll `immutable.Set`
* @define coll immutable set
*/
object Set extends ImmutableSetFactory[Set] {
override def newBuilder[A]: mutable.Builder[A, Set[A]] = new SetBuilderImpl[A]
/** $setCanBuildFromInfo */
implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, Set[A]] =
ReusableCBF.asInstanceOf[CanBuildFrom[Coll, A, Set[A]]]
private[this] val ReusableCBF = setCanBuildFrom[Any]
/** An optimized representation for immutable empty sets */
@SerialVersionUID(-2443710944435909512L)
private object EmptySet extends AbstractSet[Any] with Set[Any] with Serializable {
override def size: Int = 0
def contains(elem: Any): Boolean = false
def + (elem: Any): Set[Any] = new Set1(elem)
def - (elem: Any): Set[Any] = this
def iterator: Iterator[Any] = Iterator.empty
override def foreach[U](f: Any => U): Unit = ()
override def toSet[B >: Any]: Set[B] = this.asInstanceOf[Set[B]]
override def ++[B >: Any, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Set[Any], B, That]): That = {
if (bf eq Set.canBuildFrom) that match {
case hs: HashSet[Any] if hs.size > 4 => hs.asInstanceOf[That]
case EmptySet => EmptySet.asInstanceOf[That]
case hs: Set1[Any] => hs.asInstanceOf[That]
case hs: Set2[Any] => hs.asInstanceOf[That]
case hs: Set3[Any] => hs.asInstanceOf[That]
case hs: Set4[Any] => hs.asInstanceOf[That]
case _ => super.++(that)
}
else if (bf eq HashSet.canBuildFrom) that match {
case hs: HashSet[Any] => hs.asInstanceOf[That]
case _ => super.++(that)
} else super.++(that)
}
}
private[collection] def emptyInstance: Set[Any] = EmptySet
@SerialVersionUID(3L)
private abstract class SetNIterator[A](n: Int) extends AbstractIterator[A] with Serializable {
private[this] var current = 0
private[this] var remainder = n
def hasNext = remainder > 0
def apply(i: Int): A
def next(): A =
if (hasNext) {
val r = apply(current)
current += 1
remainder -= 1
r
} else Iterator.empty.next()
override def drop(n: Int): Iterator[A] = {
if (n > 0) {
current += n
remainder = Math.max(0, remainder - n)
}
this
}
}
/** An optimized representation for immutable sets of size 1 */
@SerialVersionUID(1233385750652442003L)
class Set1[A] private[collection] (elem1: A) extends AbstractSet[A] with Set[A] with Serializable {
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) Set.empty
else this
def iterator: Iterator[A] =
Iterator.single(elem1)
override def foreach[U](f: A => U): Unit = {
f(elem1)
}
override def exists(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1)
}
override def forall(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1)
}
override private[scala] def filterImpl(pred: A => Boolean, isFlipped: Boolean): Set[A] =
if (pred(elem1) != isFlipped) this else Set.empty
override def find(@deprecatedName('f) p: A => Boolean): Option[A] = {
if (p(elem1)) Some(elem1)
else None
}
override def head: A = elem1
override def tail: Set[A] = Set.empty
// Why is Set1 non-final? Need to fix that!
@deprecatedOverriding("This immutable set should do nothing on toSet but cast itself to a Set with a wider element type.", "2.11.8")
override def toSet[B >: A]: Set[B] = this.asInstanceOf[Set1[B]]
}
/** An optimized representation for immutable sets of size 2 */
@SerialVersionUID(-6443011234944830092L)
class Set2[A] private[collection] (elem1: A, elem2: A) extends AbstractSet[A] with Set[A] with Serializable {
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] = new SetNIterator[A](size) {
def apply(i: Int) = getElem(i)
}
private def getElem(i: Int) = i match { case 0 => elem1 case 1 => elem2 }
override def foreach[U](f: A => U): Unit = {
f(elem1); f(elem2)
}
override def exists(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1) || p(elem2)
}
override def forall(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1) && p(elem2)
}
override private[scala] def filterImpl(pred: A => Boolean, isFlipped: Boolean): Set[A] = {
var r1: A = null.asInstanceOf[A]
var n = 0
if (pred(elem1) != isFlipped) { r1 = elem1; n += 1}
if (pred(elem2) != isFlipped) { if (n == 0) r1 = elem2; n += 1}
n match {
case 0 => Set.empty
case 1 => new Set1(r1)
case 2 => this
}
}
override def find(@deprecatedName('f) p: A => Boolean): Option[A] = {
if (p(elem1)) Some(elem1)
else if (p(elem2)) Some(elem2)
else None
}
override def head: A = elem1
override def tail: Set[A] = new Set1(elem2)
// Why is Set2 non-final? Need to fix that!
@deprecatedOverriding("This immutable set should do nothing on toSet but cast itself to a Set with a wider element type.", "2.11.8")
override def toSet[B >: A]: Set[B] = this.asInstanceOf[Set2[B]]
}
/** An optimized representation for immutable sets of size 3 */
@SerialVersionUID(-3590273538119220064L)
class Set3[A] private[collection] (elem1: A, elem2: A, elem3: A) extends AbstractSet[A] with Set[A] with Serializable {
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] = new SetNIterator[A](size) {
def apply(i: Int) = getElem(i)
}
private def getElem(i: Int) = i match { case 0 => elem1 case 1 => elem2 case 2 => elem3 }
override def foreach[U](f: A => U): Unit = {
f(elem1); f(elem2); f(elem3)
}
override def exists(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1) || p(elem2) || p(elem3)
}
override def forall(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1) && p(elem2) && p(elem3)
}
override private[scala] def filterImpl(pred: A => Boolean, isFlipped: Boolean): Set[A] = {
var r1, r2: A = null.asInstanceOf[A]
var n = 0
if (pred(elem1) != isFlipped) { r1 = elem1; n += 1}
if (pred(elem2) != isFlipped) { if (n == 0) r1 = elem2 else r2 = elem2; n += 1}
if (pred(elem3) != isFlipped) { if (n == 0) r1 = elem3 else if (n == 1) r2 = elem3; n += 1}
n match {
case 0 => Set.empty
case 1 => new Set1(r1)
case 2 => new Set2(r1, r2)
case 3 => this
}
}
override def find(@deprecatedName('f) p: A => Boolean): Option[A] = {
if (p(elem1)) Some(elem1)
else if (p(elem2)) Some(elem2)
else if (p(elem3)) Some(elem3)
else None
}
override def head: A = elem1
override def tail: Set[A] = new Set2(elem2, elem3)
// Why is Set3 non-final? Need to fix that!
@deprecatedOverriding("This immutable set should do nothing on toSet but cast itself to a Set with a wider element type.", "2.11.8")
override def toSet[B >: A]: Set[B] = this.asInstanceOf[Set3[B]]
}
/** An optimized representation for immutable sets of size 4 */
@SerialVersionUID(-3622399588156184395L)
class Set4[A] private[collection] (elem1: A, elem2: A, elem3: A, elem4: A) extends AbstractSet[A] with Set[A] with Serializable {
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] = new SetNIterator[A](size) {
def apply(i: Int) = getElem(i)
}
private def getElem(i: Int) = i match { case 0 => elem1 case 1 => elem2 case 2 => elem3 case 3 => elem4 }
override def foreach[U](f: A => U): Unit = {
f(elem1); f(elem2); f(elem3); f(elem4)
}
override def exists(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1) || p(elem2) || p(elem3) || p(elem4)
}
override def forall(@deprecatedName('f) p: A => Boolean): Boolean = {
p(elem1) && p(elem2) && p(elem3) && p(elem4)
}
override private[scala] def filterImpl(pred: A => Boolean, isFlipped: Boolean): Set[A] = {
var r1, r2, r3: A = null.asInstanceOf[A]
var n = 0
if (pred(elem1) != isFlipped) { r1 = elem1; n += 1}
if (pred(elem2) != isFlipped) { if (n == 0) r1 = elem2 else r2 = elem2; n += 1}
if (pred(elem3) != isFlipped) { if (n == 0) r1 = elem3 else if (n == 1) r2 = elem3 else r3 = elem3; n += 1}
if (pred(elem4) != isFlipped) { if (n == 0) r1 = elem4 else if (n == 1) r2 = elem4 else if (n == 2) r3 = elem4; n += 1}
n match {
case 0 => Set.empty
case 1 => new Set1(r1)
case 2 => new Set2(r1, r2)
case 3 => new Set3(r1, r2, r3)
case 4 => this
}
}
override def find(@deprecatedName('f) p: A => Boolean): Option[A] = {
if (p(elem1)) Some(elem1)
else if (p(elem2)) Some(elem2)
else if (p(elem3)) Some(elem3)
else if (p(elem4)) Some(elem4)
else None
}
override def head: A = elem1
override def tail: Set[A] = new Set3(elem2, elem3, elem4)
// Why is Set4 non-final? Need to fix that!
@deprecatedOverriding("This immutable set should do nothing on toSet but cast itself to a Set with a wider element type.", "2.11.8")
override def toSet[B >: A]: Set[B] = this.asInstanceOf[Set4[B]]
}
/** Builder for Set.
*/
private final class SetBuilderImpl[A] extends mutable.ReusableBuilder[A, Set[A]] {
import scala.collection.immutable.HashSet.HashSetBuilder
private[this] var elems: Set[A] = Set.empty[A]
private[this] var switchedToHashSetBuilder: Boolean = false
private[this] var hashSetBuilder: HashSetBuilder[A] = _
override def clear(): Unit = {
elems = Set.empty[A]
if (hashSetBuilder ne null)
hashSetBuilder.clear()
switchedToHashSetBuilder = false
}
override def result(): Set[A] =
if (switchedToHashSetBuilder) hashSetBuilder.result() else elems
override def +=(elem: A) = {
if (switchedToHashSetBuilder) {
hashSetBuilder += elem
} else if (elems.size < 4) {
elems = elems + elem
} else {
// assert(elems.size == 4)
if (elems.contains(elem)) {
() // do nothing
} else {
convertToHashSetBuilder()
hashSetBuilder += elem
}
}
this
}
private def convertToHashSetBuilder(): Unit = {
switchedToHashSetBuilder = true
if (hashSetBuilder eq null)
hashSetBuilder = new HashSetBuilder
hashSetBuilder ++= elems
}
override def ++=(xs: TraversableOnce[A]): this.type = {
xs match {
case _ if switchedToHashSetBuilder =>
hashSetBuilder ++= xs
case set: collection.Set[A] if set.size > 4 =>
convertToHashSetBuilder()
hashSetBuilder ++= set
case _ => super.++= (xs)
}
this
}
}
}