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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
import scala.annotation.nowarn
trait SeqView[+A] extends SeqOps[A, View, View[A]] with View[A] {
override def view: SeqView[A] = this
override def map[B](f: A => B): SeqView[B] = new SeqView.Map(this, f)
override def appended[B >: A](elem: B): SeqView[B] = new SeqView.Appended(this, elem)
override def prepended[B >: A](elem: B): SeqView[B] = new SeqView.Prepended(elem, this)
override def reverse: SeqView[A] = new SeqView.Reverse(this)
override def take(n: Int): SeqView[A] = new SeqView.Take(this, n)
override def drop(n: Int): SeqView[A] = new SeqView.Drop(this, n)
override def takeRight(n: Int): SeqView[A] = new SeqView.TakeRight(this, n)
override def dropRight(n: Int): SeqView[A] = new SeqView.DropRight(this, n)
override def tapEach[U](f: A => U): SeqView[A] = new SeqView.Map(this, { (a: A) => f(a); a })
def concat[B >: A](suffix: SeqView.SomeSeqOps[B]): SeqView[B] = new SeqView.Concat(this, suffix)
def appendedAll[B >: A](suffix: SeqView.SomeSeqOps[B]): SeqView[B] = new SeqView.Concat(this, suffix)
def prependedAll[B >: A](prefix: SeqView.SomeSeqOps[B]): SeqView[B] = new SeqView.Concat(prefix, this)
override def sorted[B >: A](implicit ord: Ordering[B]): SeqView[A] = new SeqView.Sorted(this, ord)
@nowarn("""cat=deprecation&origin=scala\.collection\.Iterable\.stringPrefix""")
override protected[this] def stringPrefix: String = "SeqView"
}
object SeqView {
/** A `SeqOps` whose collection type and collection type constructor are unknown */
private type SomeSeqOps[+A] = SeqOps[A, AnyConstr, _]
/** A view that doesn’t apply any transformation to an underlying sequence */
@SerialVersionUID(3L)
class Id[+A](underlying: SomeSeqOps[A]) extends AbstractSeqView[A] {
def apply(idx: Int): A = underlying.apply(idx)
def length: Int = underlying.length
def iterator: Iterator[A] = underlying.iterator
override def knownSize: Int = underlying.knownSize
override def isEmpty: Boolean = underlying.isEmpty
}
@SerialVersionUID(3L)
class Map[+A, +B](underlying: SomeSeqOps[A], f: A => B) extends View.Map[A, B](underlying, f) with SeqView[B] {
def apply(idx: Int): B = f(underlying(idx))
def length: Int = underlying.length
}
@SerialVersionUID(3L)
class Appended[+A](underlying: SomeSeqOps[A], elem: A) extends View.Appended(underlying, elem) with SeqView[A] {
def apply(idx: Int): A = if (idx == underlying.length) elem else underlying(idx)
def length: Int = underlying.length + 1
}
@SerialVersionUID(3L)
class Prepended[+A](elem: A, underlying: SomeSeqOps[A]) extends View.Prepended(elem, underlying) with SeqView[A] {
def apply(idx: Int): A = if (idx == 0) elem else underlying(idx - 1)
def length: Int = underlying.length + 1
}
@SerialVersionUID(3L)
class Concat[A](prefix: SomeSeqOps[A], suffix: SomeSeqOps[A]) extends View.Concat[A](prefix, suffix) with SeqView[A] {
def apply(idx: Int): A = {
val l = prefix.length
if (idx < l) prefix(idx) else suffix(idx - l)
}
def length: Int = prefix.length + suffix.length
}
@SerialVersionUID(3L)
class Reverse[A](underlying: SomeSeqOps[A]) extends AbstractSeqView[A] {
def apply(i: Int) = underlying.apply(size - 1 - i)
def length = underlying.size
def iterator: Iterator[A] = underlying.reverseIterator
override def knownSize: Int = underlying.knownSize
override def isEmpty: Boolean = underlying.isEmpty
}
@SerialVersionUID(3L)
class Take[+A](underlying: SomeSeqOps[A], n: Int) extends View.Take(underlying, n) with SeqView[A] {
def apply(idx: Int): A = if (idx < n) {
underlying(idx)
} else {
throw new IndexOutOfBoundsException(s"$idx is out of bounds (min 0, max ${if (underlying.knownSize >= 0) knownSize - 1 else "unknown"})")
}
def length: Int = underlying.length min normN
}
@SerialVersionUID(3L)
class TakeRight[+A](underlying: SomeSeqOps[A], n: Int) extends View.TakeRight(underlying, n) with SeqView[A] {
private[this] val delta = (underlying.size - (n max 0)) max 0
def length = underlying.size - delta
@throws[IndexOutOfBoundsException]
def apply(i: Int) = underlying.apply(i + delta)
}
@SerialVersionUID(3L)
class Drop[A](underlying: SomeSeqOps[A], n: Int) extends View.Drop[A](underlying, n) with SeqView[A] {
def length = (underlying.size - normN) max 0
@throws[IndexOutOfBoundsException]
def apply(i: Int) = underlying.apply(i + normN)
override def drop(n: Int): SeqView[A] = new Drop(underlying, this.n + n)
}
@SerialVersionUID(3L)
class DropRight[A](underlying: SomeSeqOps[A], n: Int) extends View.DropRight[A](underlying, n) with SeqView[A] {
private[this] val len = (underlying.size - (n max 0)) max 0
def length = len
@throws[IndexOutOfBoundsException]
def apply(i: Int) = underlying.apply(i)
}
@SerialVersionUID(3L)
class Sorted[A, B >: A] private (private[this] var underlying: SomeSeqOps[A],
private[this] val len: Int,
ord: Ordering[B])
extends SeqView[A] {
outer =>
// force evaluation immediately by calling `length` so infinite collections
// hang on `sorted`/`sortWith`/`sortBy` rather than on arbitrary method calls
def this(underlying: SomeSeqOps[A], ord: Ordering[B]) = this(underlying, underlying.length, ord)
@SerialVersionUID(3L)
private[this] class ReverseSorted extends SeqView[A] {
private[this] lazy val _reversed = new SeqView.Reverse(_sorted)
def apply(i: Int): A = _reversed.apply(i)
def length: Int = len
def iterator: Iterator[A] = Iterator.empty ++ _reversed.iterator // very lazy
override def knownSize: Int = len
override def isEmpty: Boolean = len == 0
override def to[C1](factory: Factory[A, C1]): C1 = _reversed.to(factory)
override def reverse: SeqView[A] = outer
override protected def reversed: Iterable[A] = outer
override def sorted[B1 >: A](implicit ord1: Ordering[B1]): SeqView[A] =
if (ord1 == Sorted.this.ord) outer
else if (ord1.isReverseOf(Sorted.this.ord)) this
else new Sorted(elems, len, ord1)
}
@volatile private[this] var evaluated = false
private[this] lazy val _sorted: Seq[A] = {
val res = {
val len = this.len
if (len == 0) Nil
else if (len == 1) List(underlying.head)
else {
val arr = new Array[Any](len) // Array[Any] =:= Array[AnyRef]
underlying.copyToArray(arr)
java.util.Arrays.sort(arr.asInstanceOf[Array[AnyRef]], ord.asInstanceOf[Ordering[AnyRef]])
// casting the Array[AnyRef] to Array[A] and creating an ArraySeq from it
// is safe because:
// - the ArraySeq is immutable, and items that are not of type A
// cannot be added to it
// - we know it only contains items of type A (and if this collection
// contains items of another type, we'd get a CCE anyway)
// - the cast doesn't actually do anything in the runtime because the
// type of A is not known and Array[_] is Array[AnyRef]
immutable.ArraySeq.unsafeWrapArray(arr.asInstanceOf[Array[A]])
}
}
evaluated = true
underlying = null
res
}
private[this] def elems: SomeSeqOps[A] = {
val orig = underlying
if (evaluated) _sorted else orig
}
def apply(i: Int): A = _sorted.apply(i)
def length: Int = len
def iterator: Iterator[A] = Iterator.empty ++ _sorted.iterator // very lazy
override def knownSize: Int = len
override def isEmpty: Boolean = len == 0
override def to[C1](factory: Factory[A, C1]): C1 = _sorted.to(factory)
override def reverse: SeqView[A] = new ReverseSorted
// we know `_sorted` is either tiny or has efficient random access,
// so this is acceptable for `reversed`
override protected def reversed: Iterable[A] = new ReverseSorted
override def sorted[B1 >: A](implicit ord1: Ordering[B1]): SeqView[A] =
if (ord1 == this.ord) this
else if (ord1.isReverseOf(this.ord)) reverse
else new Sorted(elems, len, ord1)
}
}
/** Explicit instantiation of the `SeqView` trait to reduce class file size in subclasses. */
@SerialVersionUID(3L)
abstract class AbstractSeqView[+A] extends AbstractView[A] with SeqView[A]