Generate a sequence of Fibonacci number in Scala [duplicate]

Question

    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!

Answer 2

There are many ways to define the Fibonacci sequence, but my favorite is this one:

val fibs:Stream[Int] = 0 #:: 1 #:: (fibs zip fibs.tail).map{ t => t._1 + t._2 } 

This creates a stream that is evaluated lazily when you want a specific Fibonacci number.

EDIT: First, as Luigi Plinge pointed out, the "lazy" at the beginning was unnecessary. Second, go look at his answer, he pretty much did the same thing only more elegantly.