ch05_BoundedSet

BoundedSet.scala

package ch05

import scala.collection.immutable.Queue

case class BoundedSet[A](data: Queue[A],capacity: Int){
  def add(elem: A): BoundedSet[A] = {
    if (elem == null) throw new NullPointerException()
    val index = data.indexOf(elem)
    val data1 = if (index == -1) data else{
      val (f, b) = data.splitAt(index)
      f ++ b.tail
    }
    val data2 = if (data1.size == capacity) data1.tail else data1
    val data3 = data2.enqueue(elem)
    BoundedSet(data3, capacity)
  }

  def contains(elem : A): Boolean = data.contains(elem)
}

BoundedSetTests.scala

package ch05

import org.scalatest.funsuite.AnyFunSuite

import scala.collection.immutable.Queue

class BoundedSetTests extends AnyFunSuite{
  test("testSingleElement" ){
    val set = BoundedSet[Int](Queue.empty, 3)
    val set1 = set.add(1)
    assert(set1.contains(1) == true)
  }

  test("testRepeatedElement" ){
    val set = BoundedSet[Int](Queue.empty, 3)
    val set1 = set.add(1)
    val set2 = set1.add(1)
    val set3 = set2.add(1)
    val set4 = set3.add(1)
    assert(set4.contains(1) == true)
  }

  test("testOverflowKeepsSecond" ){
    val set = BoundedSet[Int](Queue.empty, 3)
    val set1 = set.add(1)
    val set2 = set1.add(2)
    val set3 = set2.add(3)
    val set4 = set3.add(4)

    assert(set4.contains(2) == true)
  }

  test("testOverflowRemovesOldest" ){
    val set = BoundedSet[Int](Queue.empty, 3)
    val set1 = set.add(1)
    val set2 = set1.add(2)
    val set3 = set2.add(3)
    val set4 = set3.add(4)

    assert(set4.contains(1) == false)
  }

  test("testOverflowKeepsNewest" ){
    val set = BoundedSet[Int](Queue.empty, 3)
    val set1 = set.add(1)
    val set2 = set1.add(2)
    val set3 = set2.add(3)
    val set4 = set3.add(4)

    assert(set4.contains(4) == true)
  }

  test("testRenewal" ){
    val set = BoundedSet[Int](Queue.empty, 3)
    val set1 = set.add(1)
    val set2 = set1.add(2)
    val set3 = set2.add(1)
    val set4 = set3.add(3)
    val set5 = set4.add(4)

    assert(set5.contains(1) == true)
  }


}