Generate a sequence of Fibonacci number in Scala [

Question

This question already has an answer here:

• What is the fastest way to write Fibonacci function in Scala? 8 answers

  def fibSeq(n: Int): List[Int] = {
    var ret = scala.collection.mutable.ListBuffer[Int](1, 2)
    while (ret(ret.length - 1) < n) {
      val temp = ret(ret.length - 1) + ret(ret.length - 2)
      if (temp >= n) {
        return ret.toList
      }
      ret += temp
    }
    ret.toList
  }

So the above is my code to generate a Fibonacci sequence using Scala to a value n. I am wondering if there is a more elegant way to do this in Scala?

Answer 1

This is a bit more elegant:

val fibs: Stream[Int] = 0 #:: fibs.scanLeft(1)(_ + _)

With Streams you "take" a number of values, which you can then turn into a List:

scala> fibs take 10 toList
res42: List[Int] = List(0, 1, 1, 2, 3, 5, 8, 13, 21, 34)

Update: I've written a blog post which goes more detail regarding how this solution works, and why you end up with a Fibonacci sequence!