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Scala example source code file (Diev.scala)

This example Scala source code file (Diev.scala) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Scala by Example" TM.

Learn more about this Scala project at its project page.

Java - Scala tags/keywords

between, boolean, coincidence, diev, enum, int, option, searchresult, show, unit, vector

The Diev.scala Scala example source code

package scalaz

import scala.annotation.tailrec
import scala.collection.mutable.ListBuffer
import syntax.enum._

/**
 * Implementation of a Discrete Interval Encoding Tree [[http://web.engr.oregonstate.edu/~erwig/diet/]] that
 * is actually implemented using a Vector and is balanced at all times as a result.
 */
sealed abstract class Diev[A] {
  def +(interval: (A, A)): Diev[A]

  def +(value: A): Diev[A]

  def -(interval: (A, A)): Diev[A]

  def -(value: A): Diev[A]

  def ++(other: Diev[A]): Diev[A]

  def --(other: Diev[A]): Diev[A]

  def intervals: Vector[(A, A)]

  def contains(value: A): Boolean

  def contains(interval: (A, A)): Boolean

  def map[B](f: A => B)(implicit EB: Enum[B]): Diev[B]

  def flatMap[B](f: A => Diev[B])(implicit EB: Enum[B]): Diev[B]

  def filter(f: A => Boolean): Diev[A]

  def foreach(f: A => Unit): Unit

  def foldLeft[B](z: B)(f: (B, A) => B): B

  def toSet(): Set[A]

  def toList(): List[A]
}

object DievInterval {
  def subtractInterval[A](minuend: (A, A), subtraend: (A, A))(implicit E: Enum[A]): Vector[(A, A)] = {
    val startOverlap = if(subtraend._1 > minuend._1) Vector((minuend._1, subtraend._1.pred)) else Vector()
    //println("startOverlap = " + startOverlap)
    val endOverlap = if(subtraend._2 < minuend._2) Vector((subtraend._2.succ, minuend._2)) else Vector()
    //println("endOverlap = " + endOverlap)
    startOverlap ++ endOverlap
  }

  def fixIntervalOrder[A](interval: (A, A))(implicit E: Enum[A]): (A, A) = if (interval._2 < interval._1) interval.swap else interval
}

trait DievImplementation {
  import syntax.std.option._
  import std.anyVal._
  import DievInterval._
  protected[this] case class DieVector[A](intervals: Vector[(A, A)] = Vector())(implicit EA: Enum[A]) extends Diev[A] {
    val liftedIntervals = intervals.lift

    private[this] sealed abstract class SearchResult
    private[this] sealed case class Coincidence(position: Int) extends SearchResult
    private[this] sealed case class Between(before: Option[Int], after: Option[Int]) extends SearchResult {
      def adjacentBefore(interval: (A, A)): Option[Int] = before.filter{pos => intervals(pos)._2.succ === interval._1}
      def adjacentAfter(interval: (A, A)): Option[Int] = after.filter{pos => intervals(pos)._1.pred === interval._2}
    }

    private def construct(prefixCount: Int, middle: Vector[(A, A)], suffixStart: Int): Diev[A] = {
      DieVector(intervals.take(prefixCount) ++ middle ++ intervals.drop(suffixStart))
    }

    private[this] def binarySearch(value: A): SearchResult = {
      @tailrec
      def innerSearch(min: Int = 0, max: Int = intervals.size): SearchResult = {
        if (max <= min) {
          val adjustedPosition = 0.max(min.min(max).min(intervals.size - 1))
          liftedIntervals(adjustedPosition) match {
            case Some((start, end)) => {
              if (start <= value && value <= end) Coincidence(adjustedPosition)
              else {
                if (value < start) Between(liftedIntervals(adjustedPosition - 1).map(_ => adjustedPosition - 1), adjustedPosition.some)
                else Between(adjustedPosition.some, liftedIntervals(adjustedPosition + 1).map(_ => adjustedPosition + 1))
              }
            }
            case _ => Between(None, None)
          }
        } else {
          val mid = min + ((max - min) / 2)

          intervals(mid) match {
            case (start, end) => {
              if (start <= value && value <= end) Coincidence(mid)
              else {
                if (value < start) innerSearch(min, mid - 1)
                else innerSearch(mid + 1, max)
              }
            }
          }
        }
      }

      val resultOfSearch = innerSearch()
      //println("resultOfSearch = " + resultOfSearch)
      resultOfSearch
    }

    def +(interval: (A, A)): Diev[A] = {
      val correctedInterval = fixIntervalOrder(interval)
      (binarySearch(correctedInterval._1), binarySearch(correctedInterval._2)) match {
        case (Coincidence(startPosition), Coincidence(endPosition)) => {
          construct(startPosition, Vector((intervals(startPosition)._1.min(correctedInterval._1), intervals(endPosition)._2.max(correctedInterval._2))), endPosition + 1)
        }
        case (Coincidence(startPosition), between@Between(_, after)) => {
          val adjacentAfterResult = between.adjacentAfter(correctedInterval)
          construct(
            startPosition,
            Vector((intervals(startPosition)._1.min(correctedInterval._1), adjacentAfterResult.map(intervals(_)._2).getOrElse(correctedInterval._2))),
            adjacentAfterResult.map(_ + 1).orElse(after).getOrElse(intervals.size)
          )
        }
        case (earlyBound@ Between(before, after), Coincidence(endPosition)) => {
          val adjacentBeforeResult = earlyBound.adjacentBefore(correctedInterval)
          construct(
            adjacentBeforeResult.orElse(before.map(_ + 1)).getOrElse(0),
            Vector((adjacentBeforeResult.map(intervals(_)._1).getOrElse(correctedInterval._1), intervals(endPosition)._2.max(correctedInterval._2))),
            endPosition + 1
          )
        }
        //(Between(None,Some(0)),Between(Some(0),Some(1)))
        case (earlyBound@ Between(before, after), lateBound@Between(_, otherAfter)) => {
          val adjacentBeforeResult = earlyBound.adjacentBefore(correctedInterval)
          val adjacentAfterResult = lateBound.adjacentAfter(correctedInterval)
          construct(
            adjacentBeforeResult.orElse(before.map(_ + 1)).getOrElse(0),
            Vector((adjacentBeforeResult.map(intervals(_)._1).getOrElse(correctedInterval._1), adjacentAfterResult.map(intervals(_)._2).getOrElse(correctedInterval._2))),
            adjacentAfterResult.map(_ + 1).orElse(otherAfter).getOrElse(intervals.size)
          )
        }
      }
    }

    def +(value: A): Diev[A] = this + (value, value)

    def -(interval: (A, A)): Diev[A] = {
      val orderedInterval = fixIntervalOrder(interval)
      (binarySearch(orderedInterval._1), binarySearch(orderedInterval._2)) match {
        case (Coincidence(startPosition), Coincidence(endPosition)) => {
          val middle = if (startPosition == endPosition) subtractInterval(intervals(startPosition), interval)
          else subtractInterval(intervals(startPosition), interval) ++ subtractInterval(intervals(endPosition), interval)
          construct(startPosition, middle, endPosition + 1)
        }
        case (Coincidence(startPosition), Between(_, endAfter)) => {
          val middle = subtractInterval(intervals(startPosition), orderedInterval)
          construct(startPosition, middle, endAfter.getOrElse(intervals.size))
        }
        case (Between(startBefore, _), Coincidence(endPosition)) => {
          val middle = subtractInterval(intervals(endPosition), orderedInterval)
          construct(startBefore.map(startBeforePos => startBeforePos + 1).orZero, middle, endPosition + 1)
        }
        case (Between(startBefore, _), Between(_, endAfter)) => {
          construct(startBefore.map(startBeforePos => startBeforePos + 1).orZero, Vector.empty, endAfter.getOrElse(intervals.size))
        }
      }
    }

    def -(value: A): Diev[A] = this - (value, value)

    def ++(other: Diev[A]): Diev[A] = other.intervals.foldLeft(this: Diev[A])(_ + _)

    def --(other: Diev[A]): Diev[A] = other.intervals.foldLeft(this: Diev[A])(_ - _)

    def contains(value: A): Boolean = binarySearch(value) match {
      case Coincidence(_) => true
      case _ => false
    }

    def contains(interval: (A, A)): Boolean = binarySearch(interval._1) match {
      case Coincidence(position) if (intervals(position)._2 >= interval._2) => true
      case _ => false
    }

    def map[B](f: A => B)(implicit EB: Enum[B]): Diev[B] = foldLeft[Diev[B]](DieVector[B]())(_ + f(_))

    def flatMap[B](f: A => Diev[B])(implicit EB: Enum[B]): Diev[B] = foldLeft[Diev[B]](DieVector[B]())(_ ++ f(_))

    def filter(f: A => Boolean): Diev[A] = foldLeft[Diev[A]](DieVector[A]())((working, value) => if (f(value)) working + value else working)

    def foreach(f: A => Unit): Unit = foldLeft[Unit](())((_, value) => f(value))

    def foldLeft[B](z: B)(f: (B, A) => B): B = {
      intervals.foldLeft(z){(z1, interval) =>
        val range = interval._1 |-> interval._2
        range.foldLeft(z1)(f)
      }
    }

    def toSet(): Set[A] = foldLeft[Set[A]](Set[A]())(_ + _)

    def toList(): List[A] = foldLeft[ListBuffer[A]](new ListBuffer())(_ += _).toList

    override def toString(): String = intervals.foldLeft(new StringBuilder().append("("))(_.append(_)).append(")").toString
  }
}

object Diev extends DievInstances {
  def empty[A](implicit E: Enum[A]): Diev[A] = DieVector()

  def fromValuesSeq[A](values: Seq[A])(implicit E: Enum[A]): Diev[A] = values.foldLeft(empty[A])(_ + _)

  def fromIntervalsSeq[A](intervals: Seq[(A, A)])(implicit E: Enum[A]): Diev[A] = intervals.foldLeft(empty[A])(_ + _)
}

sealed abstract class DievInstances extends DievImplementation {
  import std.tuple._, std.vector._

  implicit def dievEqual[A: Equal]: Equal[Diev[A]] = Equal.equalBy[Diev[A], Vector[(A, A)]](_.intervals)(std.vector.vectorEqual[(A, A)])

  implicit def dievMonoid[A: Enum]: Monoid[Diev[A]] = new Monoid[Diev[A]] {
    def append(f1: Diev[A], f2: => Diev[A]) = f1 ++ f2

    def zero: Diev[A] = new DieVector[A]()
  }

  implicit def dievShow[A: Show]: Show[Diev[A]] = new Show[Diev[A]] {
    override def show(diev: Diev[A]) = Show[Vector[(A, A)]].show(diev.intervals)
  }
}

Other Scala examples (source code examples)

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my book on functional programming

 

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