Circular.sc

// scala 2.13.4

import $ivy.`org.scalacheck::scalacheck:1.15.3`
import org.scalacheck.Gen
import scala.collection.AbstractIterator


// 11 -> 22 -> 33

class CircularIterator extends AbstractIterator[Int] {

  private var value: Int = 11

  private def inc: Unit = value match {
    case 11 => value = 22
    case 22 => value = 33
    case 33 => value = 11
  }

  override def hasNext: Boolean = true

  override def next(): Int = {
    val result = value
    inc
    result
  }
}

def genCircularInt: Gen[Int] = {
  val it = new CircularIterator
  Gen.const(0).map(_ => it.next())
}