ПСЯПР шестая

Lab6.scala

object Main extends App {
  def identity[T](value: T): T = value

  class Box[T] {
    self =>
    var value: Option[T] = None

    def save(arg: T): Unit = value = Some(arg)

    def get: T = value.get

    def map[R](f: T => R): Box[R] = new Box[R]{
      override def get: R = f(self.get)
    }

    def contraMap[R](g: R => T): Box[R] = new Box[R] {
      override def save(arg: R): Unit = self.save(g(arg))
    }

    def xmap[R](f: T => R, g: R => T): Box[R] = new Box[R]{
      override def save(arg: R): Unit = self.save(g(arg))
      override def get: R = f(self.get)
    }
  }

  def testCovariative(): Unit = {
    println("***Testing Covariative Functor***")

    val box = new Box[Int]
    box.save(51)

    val toBinaryFunc: Int => String = Integer.toBinaryString

    val mappedBox = box map toBinaryFunc
    println("Example use value:" + mappedBox.get)

    val identityBox: Box[Int] = box map identity
    println("Pass Identity Rule:" + (identityBox.get == box.get))

    val squareFunc: Int => Int = (t) => t * t
    val squaredBinaryBox = box map (squareFunc andThen toBinaryFunc)
    println("Pass Composition Rule:" + (squaredBinaryBox.get == "101000101001"))
  }

  def testContravariative(): Unit = {
    println("\n***Testing Contravariative Functor***")

    val box = new Box[Int]
    box.save(0)

    val parseFunc= (s:String)=>Integer.parseInt(s,16)

    val contraMappedBox = box contraMap parseFunc
    contraMappedBox.save("AF")
    println("Example use value:" + box.get)

    val identityBox: Box[Int] = box contraMap identity
    identityBox.save(0)
    println("Pass Identity Rule:" + (box.get==0))

    val squareFunc: Int => Int = (t) => t * t
    val squaredBinaryBox = box contraMap (parseFunc andThen squareFunc)
    val squaredBinaryBox2 = box.contraMap(squareFunc).contraMap(parseFunc)
    squaredBinaryBox.save("A")
    val result1 = box.get
    squaredBinaryBox2.save("A")
    val result2 = box.get
    println("Pass Composition Rule:" + (result1==result2))
  }

  def testInvariative(): Unit = {
    println("\n***Testing Invariative Functor***")

    val box = new Box[String]
    box.save("101")

    val toBinaryFunc: Int => String  = Integer.toBinaryString
    val fromBinaryFunc: String=>Int = i=>Integer.parseInt(i,2)

    val xBox = box xmap (fromBinaryFunc,toBinaryFunc)
    println("Example use value:" + xBox.get)

    val identityBox: Box[String] = box xmap (identity, identity)
    identityBox.save("2")
    println("Pass Identity Rule:" + (identityBox.get=="2"))

    val b1: Box[Int] = box.xmap(fromBinaryFunc, toBinaryFunc).xmap(i=>i+3,i=>i-3);
    val b2: Box[Int] = box xmap (fromBinaryFunc andThen (i=>i+3),((i:Int)=>i-3) andThen toBinaryFunc);

    b1.save(10)
    val result1 = b1.get

    b2.save(10)
    val result2 = b2.get

    println("Pass Composition Rule:" + (result1==result2))
  }

  testCovariative()
  testContravariative()
  testInvariative()
}

Не готова еще

Теперь работает