Scala example source code file (IndexedSeqLike.scala)

This example Scala source code file (IndexedSeqLike.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, abstractiterator, annotation, elements, indexedseq, int, iterablelike, iterator, repr, serializable, serialversionuid

The IndexedSeqLike.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2006-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection

import mutable.ArrayBuffer
import scala.annotation.tailrec

/** A template trait for indexed sequences of type `IndexedSeq[A]`.
 *
 *  $indexedSeqInfo
 *
 *  This trait just implements `iterator` in terms of `apply` and `length`.
 *  However, see `IndexedSeqOptimized` for an implementation trait that overrides operations
 *  to make them run faster under the assumption of fast random access with `apply`.
 *
 *  @define  Coll  IndexedSeq
 *  @define indexedSeqInfo
 *  Indexed sequences support constant-time or near constant-time element
 *  access and length computation. They are defined in terms of abstract methods
 *  `apply` for indexing and `length`.
 *
 *  Indexed sequences do not add any new methods to `Seq`, but promise
 *  efficient implementations of random access patterns.
 *
 *  @tparam A    the element type of the $coll
 *  @tparam Repr the type of the actual $coll containing the elements.
 *  @author Martin Odersky
 *  @version 2.8
 *  @since   2.8
 *  @define willNotTerminateInf
 *  @define mayNotTerminateInf
 */
trait IndexedSeqLike[+A, +Repr] extends Any with SeqLike[A, Repr] {
  self =>

  def seq: IndexedSeq[A]
  override def hashCode()= scala.util.hashing.MurmurHash3.seqHash(seq)  // TODO - can we get faster via "indexedSeqHash" ?

  override protected[this] def thisCollection: IndexedSeq[A] = this.asInstanceOf[IndexedSeq[A]]
  override protected[this] def toCollection(repr: Repr): IndexedSeq[A] = repr.asInstanceOf[IndexedSeq[A]]

  /** The class of the iterator returned by the `iterator` method.
   *  multiple `take`, `drop`, and `slice` operations on this iterator are bunched
   *  together for better efficiency.
   */
  // pre: start >= 0, end <= self.length
  @SerialVersionUID(1756321872811029277L)
  protected class Elements(start: Int, end: Int) extends AbstractIterator[A] with BufferedIterator[A] with Serializable {
    private var index = start
    private def available = (end - index) max 0

    def hasNext: Boolean = index < end

    def next(): A = {
      if (index >= end)
        Iterator.empty.next()

      val x = self(index)
      index += 1
      x
    }

    def head = {
      if (index >= end)
        Iterator.empty.next()

      self(index)
    }

    override def drop(n: Int): Iterator[A] =
      if (n <= 0) new Elements(index, end)
      else if (index + n >= end) new Elements(end, end)
      else new Elements(index + n, end)
    override def take(n: Int): Iterator[A] =
      if (n <= 0) Iterator.empty
      else if (n <= available) new Elements(index, index + n)
      else new Elements(index, end)
    override def slice(from: Int, until: Int): Iterator[A] =
      this take until drop from
  }

  override /*IterableLike*/
  def iterator: Iterator[A] = new Elements(0, length)

  /* Overridden for efficiency */
  override def toBuffer[A1 >: A]: mutable.Buffer[A1] = {
    val result = new mutable.ArrayBuffer[A1](size)
    copyToBuffer(result)
    result
  }
}