Scala example source code file (ArrayOps.scala)

This example Scala source code file (ArrayOps.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

anyval, array, arraylike, arrayops, b, classtag, int, reflection, t, t2, wrappedarray

The ArrayOps.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection
package mutable

import scala.compat.Platform.arraycopy
import scala.reflect.ClassTag
import scala.runtime.ScalaRunTime._
import parallel.mutable.ParArray

/** This class serves as a wrapper for `Array`s with all the operations found in
 *  indexed sequences. Where needed, instances of arrays are implicitly converted
 *  into this class.
 *
 *  The difference between this class and `WrappedArray` is that calling transformer
 *  methods such as `filter` and `map` will yield an array, whereas a `WrappedArray`
 *  will remain a `WrappedArray`.
 *
 *  @since 2.8
 *
 *  @tparam T   type of the elements contained in this array.
 *
 *  @define Coll `Array`
 *  @define orderDependent
 *  @define orderDependentFold
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 */
@deprecatedInheritance("ArrayOps will be sealed to facilitate greater flexibility with array/collections integration in future releases.", "2.11.0")
trait ArrayOps[T] extends Any with ArrayLike[T, Array[T]] with CustomParallelizable[T, ParArray[T]] {

  private def elementClass: Class[_] =
    arrayElementClass(repr.getClass)

  override def copyToArray[U >: T](xs: Array[U], start: Int, len: Int) {
    var l = math.min(len, repr.length)
    if (xs.length - start < l) l = xs.length - start max 0
    Array.copy(repr, 0, xs, start, l)
  }

  override def toArray[U >: T : ClassTag]: Array[U] = {
    val thatElementClass = arrayElementClass(implicitly[ClassTag[U]])
    if (elementClass eq thatElementClass)
      repr.asInstanceOf[Array[U]]
    else
      super.toArray[U]
  }

  def :+[B >: T: ClassTag](elem: B): Array[B] = {
    val result = Array.ofDim[B](repr.length + 1)
    Array.copy(repr, 0, result, 0, repr.length)
    result(repr.length) = elem
    result
  }

  def +:[B >: T: ClassTag](elem: B): Array[B] = {
    val result = Array.ofDim[B](repr.length + 1)
    result(0) = elem
    Array.copy(repr, 0, result, 1, repr.length)
    result
  }

  override def par = ParArray.handoff(repr)

  /** Flattens a two-dimensional array by concatenating all its rows
   *  into a single array.
   *
   *  @tparam U        Type of row elements.
   *  @param asTrav    A function that converts elements of this array to rows - arrays of type `U`.
   *  @return          An array obtained by concatenating rows of this array.
   */
  def flatten[U](implicit asTrav: T => scala.collection.Traversable[U], m: ClassTag[U]): Array[U] = {
    val b = Array.newBuilder[U]
    b.sizeHint(map{case is: scala.collection.IndexedSeq[_] => is.size case _ => 0}.sum)
    for (xs <- this)
      b ++= asTrav(xs)
    b.result()
  }

  /** Transposes a two dimensional array.
   *
   *  @tparam U       Type of row elements.
   *  @param asArray  A function that converts elements of this array to rows - arrays of type `U`.
   *  @return         An array obtained by replacing elements of this arrays with rows the represent.
   */
  def transpose[U](implicit asArray: T => Array[U]): Array[Array[U]] = {
    val bb: Builder[Array[U], Array[Array[U]]] = Array.newBuilder(ClassTag[Array[U]](elementClass))
    if (isEmpty) bb.result()
    else {
      def mkRowBuilder() = Array.newBuilder(ClassTag[U](arrayElementClass(elementClass)))
      val bs = asArray(head) map (_ => mkRowBuilder())
      for (xs <- this) {
        var i = 0
        for (x <- asArray(xs)) {
          bs(i) += x
          i += 1
        }
      }
      for (b <- bs) bb += b.result()
      bb.result()
    }
  }
  
  /** Converts an array of pairs into an array of first elements and an array of second elements.
   *  
   *  @tparam T1    the type of the first half of the element pairs
   *  @tparam T2    the type of the second half of the element pairs
   *  @param asPair an implicit conversion which asserts that the element type
   *                of this Array is a pair.
   *  @param ct1    a class tag for T1 type parameter that is required to create an instance
   *                of Array[T1]
   *  @param ct2    a class tag for T2 type parameter that is required to create an instance
   *                of Array[T2]
   *  @return       a pair of Arrays, containing, respectively, the first and second half
   *                of each element pair of this Array.
   */
  // implementation NOTE: ct1 and ct2 can't be written as context bounds because desugared
  // implicits are put in front of asPair parameter that is supposed to guide type inference
  def unzip[T1, T2](implicit asPair: T => (T1, T2), ct1: ClassTag[T1], ct2: ClassTag[T2]): (Array[T1], Array[T2]) = {
    val a1 = new Array[T1](length)
    val a2 = new Array[T2](length)
    var i = 0
    while (i < length) {
      val e = apply(i)
      a1(i) = e._1
      a2(i) = e._2
      i += 1
    }
    (a1, a2)
  }
  
  /** Converts an array of triples into three arrays, one containing the elements from each position of the triple.
   *  
   *  @tparam T1      the type of the first of three elements in the triple
   *  @tparam T2      the type of the second of three elements in the triple
   *  @tparam T3      the type of the third of three elements in the triple
   *  @param asTriple an implicit conversion which asserts that the element type
   *                  of this Array is a triple.
   *  @param ct1    a class tag for T1 type parameter that is required to create an instance
   *                of Array[T1]
   *  @param ct2    a class tag for T2 type parameter that is required to create an instance
   *                of Array[T2]
   *  @param ct3    a class tag for T3 type parameter that is required to create an instance
   *                of Array[T3]
   *  @return         a triple of Arrays, containing, respectively, the first, second, and third
   *                  elements from each element triple of this Array.
   */
  // implementation NOTE: ct1, ct2, ct3 can't be written as context bounds because desugared
  // implicits are put in front of asPair parameter that is supposed to guide type inference
  def unzip3[T1, T2, T3](implicit asTriple: T => (T1, T2, T3), ct1: ClassTag[T1], ct2: ClassTag[T2],
    ct3: ClassTag[T3]): (Array[T1], Array[T2], Array[T3]) = {
    val a1 = new Array[T1](length)
    val a2 = new Array[T2](length)
    val a3 = new Array[T3](length)
    var i = 0
    while (i < length) {
      val e = apply(i)
      a1(i) = e._1
      a2(i) = e._2
      a3(i) = e._3
      i += 1
    }
    (a1, a2, a3)
  }
  

  def seq = thisCollection

}

/**
 * A companion object for `ArrayOps`.
 *
 * @since 2.8
 */
object ArrayOps {

  /** A class of `ArrayOps` for arrays containing reference types. */
  final class ofRef[T <: AnyRef](override val repr: Array[T]) extends AnyVal with ArrayOps[T] with ArrayLike[T, Array[T]] {

    override protected[this] def thisCollection: WrappedArray[T] = new WrappedArray.ofRef[T](repr)
    override protected[this] def toCollection(repr: Array[T]): WrappedArray[T] = new WrappedArray.ofRef[T](repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofRef[T]()(ClassTag[T](arrayElementClass(repr.getClass)))

    def length: Int = repr.length
    def apply(index: Int): T = repr(index)
    def update(index: Int, elem: T) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `byte`s. */
final class ofByte(override val repr: Array[Byte]) extends AnyVal with ArrayOps[Byte] with ArrayLike[Byte, Array[Byte]] {

    override protected[this] def thisCollection: WrappedArray[Byte] = new WrappedArray.ofByte(repr)
    override protected[this] def toCollection(repr: Array[Byte]): WrappedArray[Byte] = new WrappedArray.ofByte(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofByte

    def length: Int = repr.length
    def apply(index: Int): Byte = repr(index)
    def update(index: Int, elem: Byte) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `short`s. */
final class ofShort(override val repr: Array[Short]) extends AnyVal with ArrayOps[Short] with ArrayLike[Short, Array[Short]] {

    override protected[this] def thisCollection: WrappedArray[Short] = new WrappedArray.ofShort(repr)
    override protected[this] def toCollection(repr: Array[Short]): WrappedArray[Short] = new WrappedArray.ofShort(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofShort

    def length: Int = repr.length
    def apply(index: Int): Short = repr(index)
    def update(index: Int, elem: Short) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `char`s. */
final class ofChar(override val repr: Array[Char]) extends AnyVal with ArrayOps[Char] with ArrayLike[Char, Array[Char]] {

    override protected[this] def thisCollection: WrappedArray[Char] = new WrappedArray.ofChar(repr)
    override protected[this] def toCollection(repr: Array[Char]): WrappedArray[Char] = new WrappedArray.ofChar(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofChar

    def length: Int = repr.length
    def apply(index: Int): Char = repr(index)
    def update(index: Int, elem: Char) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `int`s. */
final class ofInt(override val repr: Array[Int]) extends AnyVal with ArrayOps[Int] with ArrayLike[Int, Array[Int]] {

    override protected[this] def thisCollection: WrappedArray[Int] = new WrappedArray.ofInt(repr)
    override protected[this] def toCollection(repr: Array[Int]): WrappedArray[Int] = new WrappedArray.ofInt(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofInt

    def length: Int = repr.length
    def apply(index: Int): Int = repr(index)
    def update(index: Int, elem: Int) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `long`s. */
final class ofLong(override val repr: Array[Long]) extends AnyVal with ArrayOps[Long] with ArrayLike[Long, Array[Long]] {

    override protected[this] def thisCollection: WrappedArray[Long] = new WrappedArray.ofLong(repr)
    override protected[this] def toCollection(repr: Array[Long]): WrappedArray[Long] = new WrappedArray.ofLong(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofLong

    def length: Int = repr.length
    def apply(index: Int): Long = repr(index)
    def update(index: Int, elem: Long) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `float`s. */
final class ofFloat(override val repr: Array[Float]) extends AnyVal with ArrayOps[Float] with ArrayLike[Float, Array[Float]] {

    override protected[this] def thisCollection: WrappedArray[Float] = new WrappedArray.ofFloat(repr)
    override protected[this] def toCollection(repr: Array[Float]): WrappedArray[Float] = new WrappedArray.ofFloat(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofFloat

    def length: Int = repr.length
    def apply(index: Int): Float = repr(index)
    def update(index: Int, elem: Float) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `double`s. */
final class ofDouble(override val repr: Array[Double]) extends AnyVal with ArrayOps[Double] with ArrayLike[Double, Array[Double]] {

    override protected[this] def thisCollection: WrappedArray[Double] = new WrappedArray.ofDouble(repr)
    override protected[this] def toCollection(repr: Array[Double]): WrappedArray[Double] = new WrappedArray.ofDouble(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofDouble

    def length: Int = repr.length
    def apply(index: Int): Double = repr(index)
    def update(index: Int, elem: Double) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays containing `boolean`s. */
final class ofBoolean(override val repr: Array[Boolean]) extends AnyVal with ArrayOps[Boolean] with ArrayLike[Boolean, Array[Boolean]] {

    override protected[this] def thisCollection: WrappedArray[Boolean] = new WrappedArray.ofBoolean(repr)
    override protected[this] def toCollection(repr: Array[Boolean]): WrappedArray[Boolean] = new WrappedArray.ofBoolean(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofBoolean

    def length: Int = repr.length
    def apply(index: Int): Boolean = repr(index)
    def update(index: Int, elem: Boolean) { repr(index) = elem }
  }

  /** A class of `ArrayOps` for arrays of `Unit` types. */
final class ofUnit(override val repr: Array[Unit]) extends AnyVal with ArrayOps[Unit] with ArrayLike[Unit, Array[Unit]] {

    override protected[this] def thisCollection: WrappedArray[Unit] = new WrappedArray.ofUnit(repr)
    override protected[this] def toCollection(repr: Array[Unit]): WrappedArray[Unit] = new WrappedArray.ofUnit(repr)
    override protected[this] def newBuilder = new ArrayBuilder.ofUnit

    def length: Int = repr.length
    def apply(index: Int): Unit = repr(index)
    def update(index: Int, elem: Unit) { repr(index) = elem }
  }
}