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Scala example source code file (LongMap.scala)

This example Scala source code file (LongMap.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

annotation, b, collection, generics, long, longmap, longmapiterator, mutable, none, s, si-5548, some, t, unit

The LongMap.scala Scala example source code

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

package scala
package collection
package immutable

import scala.collection.generic.{ CanBuildFrom, BitOperations }
import scala.collection.mutable.{ Builder, MapBuilder }
import scala.annotation.tailrec

/** Utility class for long maps.
 *  @author David MacIver
 */
private[immutable] object LongMapUtils extends BitOperations.Long {
  def branchMask(i: Long, j: Long) = highestOneBit(i ^ j)

  def join[T](p1: Long, t1: LongMap[T], p2: Long, t2: LongMap[T]): LongMap[T] = {
    val m = branchMask(p1, p2)
    val p = mask(p1, m)
    if (zero(p1, m)) LongMap.Bin(p, m, t1, t2)
    else LongMap.Bin(p, m, t2, t1)
  }

  def bin[T](prefix: Long, mask: Long, left: LongMap[T], right: LongMap[T]): LongMap[T] = (left, right) match {
    case (left, LongMap.Nil) => left
    case (LongMap.Nil, right) => right
    case (left, right) => LongMap.Bin(prefix, mask, left, right)
  }
}

import LongMapUtils._

/** A companion object for long maps.
 *
 *  @define Coll  `LongMap`
 *  @define mapCanBuildFromInfo
 *    The standard `CanBuildFrom` instance for `$Coll` objects.
 *    The created value is an instance of class `MapCanBuildFrom`.
 *  @since 2.7
 */
object LongMap {
  /** $mapCanBuildFromInfo */
  implicit def canBuildFrom[A, B] = new CanBuildFrom[LongMap[A], (Long, B), LongMap[B]] {
    def apply(from: LongMap[A]): Builder[(Long, B), LongMap[B]] = apply()
    def apply(): Builder[(Long, B), LongMap[B]] = new MapBuilder[Long, B, LongMap[B]](empty[B])
  }

  def empty[T]: LongMap[T]  = LongMap.Nil
  def singleton[T](key: Long, value: T): LongMap[T] = LongMap.Tip(key, value)
  def apply[T](elems: (Long, T)*): LongMap[T] =
    elems.foldLeft(empty[T])((x, y) => x.updated(y._1, y._2))

  private[immutable] case object Nil extends LongMap[Nothing] {
    // Important, don't remove this! See IntMap for explanation.
    override def equals(that : Any) = that match {
      case (that: AnyRef) if (this eq that) => true
      case (that: LongMap[_]) => false // The only empty LongMaps are eq Nil
      case that => super.equals(that)
    }
  }

  private[immutable] case class Tip[+T](key: Long, value: T) extends LongMap[T] {
    def withValue[S](s: S) =
      if (s.asInstanceOf[AnyRef] eq value.asInstanceOf[AnyRef]) this.asInstanceOf[LongMap.Tip[S]]
      else LongMap.Tip(key, s)
  }
  private[immutable] case class Bin[+T](prefix: Long, mask: Long, left: LongMap[T], right: LongMap[T]) extends LongMap[T] {
    def bin[S](left: LongMap[S], right: LongMap[S]): LongMap[S] = {
      if ((this.left eq left) && (this.right eq right)) this.asInstanceOf[LongMap.Bin[S]]
      else LongMap.Bin[S](prefix, mask, left, right)
    }
  }
}

// Iterator over a non-empty LongMap.
private[immutable] abstract class LongMapIterator[V, T](it: LongMap[V]) extends AbstractIterator[T] {

  // Basically this uses a simple stack to emulate conversion over the tree. However
  // because we know that Longs are only 64 bits we can have at most 64 LongMap.Bins and
  // one LongMap.Tip sitting on the tree at any point. Therefore we know the maximum stack
  // depth is 65
  var index = 0
  var buffer = new Array[AnyRef](65)

  def pop() = {
    index -= 1
    buffer(index).asInstanceOf[LongMap[V]]
  }

  def push(x: LongMap[V]) {
    buffer(index) = x.asInstanceOf[AnyRef]
    index += 1
  }
  push(it)

  /**
   * What value do we assign to a tip?
   */
  def valueOf(tip: LongMap.Tip[V]): T

  def hasNext = index != 0
  final def next: T =
    pop() match {
      case LongMap.Bin(_,_, t@LongMap.Tip(_, _), right) => {
        push(right)
        valueOf(t)
      }
      case LongMap.Bin(_, _, left, right) => {
        push(right)
        push(left)
        next
      }
      case t@LongMap.Tip(_, _) => valueOf(t)
      // This should never happen. We don't allow LongMap.Nil in subtrees of the LongMap
      // and don't return an LongMapIterator for LongMap.Nil.
      case LongMap.Nil => sys.error("Empty maps not allowed as subtrees")
    }
}

private[immutable] class LongMapEntryIterator[V](it: LongMap[V]) extends LongMapIterator[V, (Long, V)](it){
  def valueOf(tip: LongMap.Tip[V]) = (tip.key, tip.value)
}

private[immutable] class LongMapValueIterator[V](it: LongMap[V]) extends LongMapIterator[V, V](it){
  def valueOf(tip: LongMap.Tip[V]) = tip.value
}

private[immutable] class LongMapKeyIterator[V](it: LongMap[V]) extends LongMapIterator[V, Long](it){
  def valueOf(tip: LongMap.Tip[V]) = tip.key
}

/**
 *  Specialised immutable map structure for long keys, based on
 *  <a href="http://citeseer.ist.psu.edu/okasaki98fast.html">Fast Mergeable Long Maps</a>
 *  by Okasaki and Gill. Essentially a trie based on binary digits of the integers.
 *
 *  Note: This class is as of 2.8 largely superseded by HashMap.
 *
 *  @tparam T      type of the values associated with the long keys.
 *
 *  @since 2.7
 *  @define Coll `immutable.LongMap`
 *  @define coll immutable long integer map
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 */
sealed abstract class LongMap[+T]
extends AbstractMap[Long, T]
   with Map[Long, T]
   with MapLike[Long, T, LongMap[T]] {

  override def empty: LongMap[T] = LongMap.Nil

  override def toList = {
    val buffer = new scala.collection.mutable.ListBuffer[(Long, T)]
    foreach(buffer += _)
    buffer.toList
  }

  /**
   * Iterator over key, value pairs of the map in unsigned order of the keys.
   *
   * @return an iterator over pairs of long keys and corresponding values.
   */
  def iterator: Iterator[(Long, T)] = this match {
    case LongMap.Nil => Iterator.empty
    case _ => new LongMapEntryIterator(this)
  }

  /**
   * Loops over the key, value pairs of the map in unsigned order of the keys.
   */
  override final def foreach[U](f: ((Long, T)) =>  U): Unit = this match {
    case LongMap.Bin(_, _, left, right) => { left.foreach(f); right.foreach(f) }
    case LongMap.Tip(key, value) => f((key, value))
    case LongMap.Nil =>
  }

  override def keysIterator: Iterator[Long] = this match {
    case LongMap.Nil => Iterator.empty
    case _ => new LongMapKeyIterator(this)
  }

  /**
   * Loop over the keys of the map. The same as keys.foreach(f), but may
   * be more efficient.
   *
   * @param f The loop body
   */
  final def foreachKey(f: Long => Unit): Unit = this match {
    case LongMap.Bin(_, _, left, right) => { left.foreachKey(f); right.foreachKey(f) }
    case LongMap.Tip(key, _) => f(key)
    case LongMap.Nil =>
  }

  override def valuesIterator: Iterator[T] = this match {
    case LongMap.Nil => Iterator.empty
    case _ => new LongMapValueIterator(this)
  }

  /**
   * Loop over the values of the map. The same as values.foreach(f), but may
   * be more efficient.
   *
   * @param f The loop body
   */
  final def foreachValue(f: T => Unit): Unit = this match {
    case LongMap.Bin(_, _, left, right) => { left.foreachValue(f); right.foreachValue(f) }
    case LongMap.Tip(_, value) => f(value)
    case LongMap.Nil =>
  }

  override def stringPrefix = "LongMap"

  override def isEmpty = this == LongMap.Nil

  override def filter(f: ((Long, T)) => Boolean): LongMap[T] = this match {
    case LongMap.Bin(prefix, mask, left, right) => {
      val (newleft, newright) = (left.filter(f), right.filter(f))
      if ((left eq newleft) && (right eq newright)) this
      else bin(prefix, mask, newleft, newright)
    }
    case LongMap.Tip(key, value) =>
      if (f((key, value))) this
      else LongMap.Nil
    case LongMap.Nil => LongMap.Nil
  }

  def transform[S](f: (Long, T) => S): LongMap[S] = this match {
    case b@LongMap.Bin(prefix, mask, left, right) => b.bin(left.transform(f), right.transform(f))
    case t@LongMap.Tip(key, value) => t.withValue(f(key, value))
    case LongMap.Nil => LongMap.Nil
  }

  final override def size: Int = this match {
    case LongMap.Nil => 0
    case LongMap.Tip(_, _) => 1
    case LongMap.Bin(_, _, left, right) => left.size + right.size
  }

  final def get(key: Long): Option[T] = this match {
    case LongMap.Bin(prefix, mask, left, right) => if (zero(key, mask)) left.get(key) else right.get(key)
    case LongMap.Tip(key2, value) => if (key == key2) Some(value) else None
    case LongMap.Nil => None
  }

  final override def getOrElse[S >: T](key: Long, default: => S): S = this match {
    case LongMap.Nil => default
    case LongMap.Tip(key2, value) => if (key == key2) value else default
    case LongMap.Bin(prefix, mask, left, right) =>
      if (zero(key, mask)) left.getOrElse(key, default) else right.getOrElse(key, default)
  }

  final override def apply(key: Long): T = this match {
    case LongMap.Bin(prefix, mask, left, right) => if (zero(key, mask)) left(key) else right(key)
    case LongMap.Tip(key2, value) => if (key == key2) value else sys.error("Key not found")
    case LongMap.Nil => sys.error("key not found")
  }

  def + [S >: T] (kv: (Long, S)): LongMap[S] = updated(kv._1, kv._2)

  override def updated[S >: T](key: Long, value: S): LongMap[S] = this match {
    case LongMap.Bin(prefix, mask, left, right) =>
      if (!hasMatch(key, prefix, mask)) join(key, LongMap.Tip(key, value), prefix, this)
      else if (zero(key, mask)) LongMap.Bin(prefix, mask, left.updated(key, value), right)
      else LongMap.Bin(prefix, mask, left, right.updated(key, value))
    case LongMap.Tip(key2, value2) =>
      if (key == key2) LongMap.Tip(key, value)
      else join(key, LongMap.Tip(key, value), key2, this)
    case LongMap.Nil => LongMap.Tip(key, value)
  }

  /**
   * Updates the map, using the provided function to resolve conflicts if the key is already present.
   *
   * Equivalent to
   * {{{
   *   this.get(key) match {
   *     case None => this.update(key, value)
   *     case Some(oldvalue) => this.update(key, f(oldvalue, value)
   *   }
   * }}}
   *
   * @tparam S     The supertype of values in this `LongMap`.
   * @param key    The key to update.
   * @param value  The value to use if there is no conflict.
   * @param f      The function used to resolve conflicts.
   * @return       The updated map.
   */
  def updateWith[S >: T](key: Long, value: S, f: (T, S) => S): LongMap[S] = this match {
    case LongMap.Bin(prefix, mask, left, right) =>
      if (!hasMatch(key, prefix, mask)) join(key, LongMap.Tip(key, value), prefix, this)
      else if (zero(key, mask)) LongMap.Bin(prefix, mask, left.updateWith(key, value, f), right)
      else LongMap.Bin(prefix, mask, left, right.updateWith(key, value, f))
    case LongMap.Tip(key2, value2) =>
      if (key == key2) LongMap.Tip(key, f(value2, value))
      else join(key, LongMap.Tip(key, value), key2, this)
    case LongMap.Nil => LongMap.Tip(key, value)
  }

  def -(key: Long): LongMap[T] = this match {
    case LongMap.Bin(prefix, mask, left, right) =>
      if (!hasMatch(key, prefix, mask)) this
      else if (zero(key, mask)) bin(prefix, mask, left - key, right)
      else bin(prefix, mask, left, right - key)
    case LongMap.Tip(key2, _) =>
      if (key == key2) LongMap.Nil
      else this
    case LongMap.Nil => LongMap.Nil
  }

  /**
   * A combined transform and filter function. Returns an `LongMap` such that
   * for each `(key, value)` mapping in this map, if `f(key, value) == None`
   * the map contains no mapping for key, and if `f(key, value)`.
   *
   * @tparam S    The type of the values in the resulting `LongMap`.
   * @param f     The transforming function.
   * @return      The modified map.
   */
  def modifyOrRemove[S](f: (Long, T) => Option[S]): LongMap[S] = this match {
      case LongMap.Bin(prefix, mask, left, right) => {
        val newleft = left.modifyOrRemove(f)
        val newright = right.modifyOrRemove(f)
        if ((left eq newleft) && (right eq newright)) this.asInstanceOf[LongMap[S]]
        else bin(prefix, mask, newleft, newright)
      }
    case LongMap.Tip(key, value) => f(key, value) match {
      case None => LongMap.Nil
      case Some(value2) =>
        //hack to preserve sharing
        if (value.asInstanceOf[AnyRef] eq value2.asInstanceOf[AnyRef]) this.asInstanceOf[LongMap[S]]
        else LongMap.Tip(key, value2)
      }
    case LongMap.Nil => LongMap.Nil
  }

  /**
   * Forms a union map with that map, using the combining function to resolve conflicts.
   *
   * @tparam S      The type of values in `that`, a supertype of values in `this`.
   * @param that    The map to form a union with.
   * @param f       The function used to resolve conflicts between two mappings.
   * @return        Union of `this` and `that`, with identical key conflicts resolved using the function `f`.
   */
  def unionWith[S >: T](that: LongMap[S], f: (Long, S, S) => S): LongMap[S] = (this, that) match{
    case (LongMap.Bin(p1, m1, l1, r1), that@(LongMap.Bin(p2, m2, l2, r2))) =>
      if (shorter(m1, m2)) {
        if (!hasMatch(p2, p1, m1)) join[S](p1, this, p2, that) // TODO: remove [S] when SI-5548 is fixed
        else if (zero(p2, m1)) LongMap.Bin(p1, m1, l1.unionWith(that, f), r1)
        else LongMap.Bin(p1, m1, l1, r1.unionWith(that, f))
      } else if (shorter(m2, m1)){
        if (!hasMatch(p1, p2, m2)) join[S](p1, this, p2, that) // TODO: remove [S] when SI-5548 is fixed
        else if (zero(p1, m2)) LongMap.Bin(p2, m2, this.unionWith(l2, f), r2)
        else LongMap.Bin(p2, m2, l2, this.unionWith(r2, f))
      }
      else {
        if (p1 == p2) LongMap.Bin(p1, m1, l1.unionWith(l2,f), r1.unionWith(r2, f))
        else join[S](p1, this, p2, that) // TODO: remove [S] when SI-5548 is fixed
      }
    case (LongMap.Tip(key, value), x) => x.updateWith[S](key, value, (x, y) => f(key, y, x)) // TODO: remove [S] when SI-5548 is fixed
    case (x, LongMap.Tip(key, value)) => x.updateWith[S](key, value, (x, y) => f(key, x, y))
    case (LongMap.Nil, x) => x
    case (x, LongMap.Nil) => x
  }

  /**
   * Forms the intersection of these two maps with a combining function. The
   * resulting map is a map that has only keys present in both maps and has
   * values produced from the original mappings by combining them with `f`.
   *
   * @tparam S      The type of values in `that`.
   * @tparam R      The type of values in the resulting `LongMap`.
   * @param that    The map to intersect with.
   * @param f       The combining function.
   * @return        Intersection of `this` and `that`, with values for identical keys produced by function `f`.
   */
  def intersectionWith[S, R](that: LongMap[S], f: (Long, T, S) => R): LongMap[R] = (this, that) match {
    case (LongMap.Bin(p1, m1, l1, r1), that@LongMap.Bin(p2, m2, l2, r2)) =>
      if (shorter(m1, m2)) {
        if (!hasMatch(p2, p1, m1)) LongMap.Nil
        else if (zero(p2, m1)) l1.intersectionWith(that, f)
        else r1.intersectionWith(that, f)
      } else if (m1 == m2) bin(p1, m1, l1.intersectionWith(l2, f), r1.intersectionWith(r2, f))
        else {
        if (!hasMatch(p1, p2, m2)) LongMap.Nil
        else if (zero(p1, m2)) this.intersectionWith(l2, f)
        else this.intersectionWith(r2, f)
      }
    case (LongMap.Tip(key, value), that) => that.get(key) match {
      case None => LongMap.Nil
      case Some(value2) => LongMap.Tip(key, f(key, value, value2))
    }
    case (_, LongMap.Tip(key, value)) => this.get(key) match {
      case None => LongMap.Nil
      case Some(value2) => LongMap.Tip(key, f(key, value2, value))
    }
    case (_, _) => LongMap.Nil
  }

  /**
   * Left biased intersection. Returns the map that has all the same mappings as this but only for keys
   * which are present in the other map.
   *
   * @tparam R      The type of values in `that`.
   * @param that    The map to intersect with.
   * @return        A map with all the keys both in `this` and `that`, mapped to corresponding values from `this`.
   */
  def intersection[R](that: LongMap[R]): LongMap[T] =
    this.intersectionWith(that, (key: Long, value: T, value2: R) => value)

  def ++[S >: T](that: LongMap[S]) =
    this.unionWith[S](that, (key, x, y) => y)

  @tailrec
  final def firstKey: Long = this match {
    case LongMap.Bin(_, _, l, r) => l.firstKey
    case LongMap.Tip(k, v) => k
    case LongMap.Nil => sys.error("Empty set")
  }

  @tailrec
  final def lastKey: Long = this match {
    case LongMap.Bin(_, _, l, r) => r.lastKey
    case LongMap.Tip(k , v) => k
    case LongMap.Nil => sys.error("Empty set")
  }

}

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