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scalalazy-evaluationscala-2.13

Scala compilation issue "forward reference extends over definition of value"

Compilation error occurs for the below snippet only when it is method level implementation and error does not occur when it is defined in main. What is the difference ? Scala version used is 2.13.5.

class FibonacciGenerator  {
  def generate(total: Int): List[Int] = {
    val fibSeries: LazyList[Int] = LazyList.cons(1, LazyList.cons(1, fibSeries.zip(fibSeries.tail).map { t => t._1 + t._2 }))
    fibSeries.take(total).toList
  }
}

Same implementation does not fail below.

object Misc extends App {

  val x: LazyList[Int] = LazyList.cons(1, LazyList.cons(1, x.zip(x.tail).map{t => t._1 + t._2}))
  println(x)
  println(x.take(10).toList)
Solution

  • The difference is that in the latter case you are using objects which are created lazily

    An object... is created lazily when it is referenced, like a lazy val.

    In the first case it should work if you declare lazy val fibSeries.