Scala example source code file (LazyCombiner.scala)

This example Scala source code file (LazyCombiner.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

arraybuffer, buff, cannot, collection, combiner, elem, generics, growable, lazycombiner, mutable, newto, parallel, see, to

The LazyCombiner.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection.parallel.mutable

import scala.collection.generic.Growable
import scala.collection.generic.Sizing
import scala.collection.mutable.ArrayBuffer
import scala.collection.parallel.Combiner

/** Implements combining contents of two combiners
 *  by postponing the operation until `result` method is called. It chains
 *  the leaf results together instead of evaluating the actual collection.
 *
 *  @tparam Elem    the type of the elements in the combiner
 *  @tparam To      the type of the collection the combiner produces
 *  @tparam Buff    the type of the buffers that contain leaf results and this combiner chains together
 */
trait LazyCombiner[Elem, +To, Buff <: Growable[Elem] with Sizing] extends Combiner[Elem, To] {
//self: scala.collection.parallel.EnvironmentPassingCombiner[Elem, To] =>
  val chain: ArrayBuffer[Buff]
  val lastbuff = chain.last
  def +=(elem: Elem) = { lastbuff += elem; this }
  def result: To = allocateAndCopy
  def clear() = { chain.clear() }
  def combine[N <: Elem, NewTo >: To](other: Combiner[N, NewTo]): Combiner[N, NewTo] = if (this ne other) {
    import language.existentials // FIXME: See SI-7750
    if (other.isInstanceOf[LazyCombiner[_, _, _]]) {
      val that = other.asInstanceOf[LazyCombiner[Elem, To, Buff]]
      newLazyCombiner(chain ++= that.chain)
    } else throw new UnsupportedOperationException("Cannot combine with combiner of different type.")
  } else this
  def size = chain.foldLeft(0)(_ + _.size)

  /** Method that allocates the data structure and copies elements into it using
   *  `size` and `chain` members.
   */
  def allocateAndCopy: To
  def newLazyCombiner(buffchain: ArrayBuffer[Buff]): LazyCombiner[Elem, To, Buff]
}