How to return a function in scala

Question

How can I return a function side-effecting lexical closure¹ in Scala?

For instance, I was looking at this code sample in Go:

Answer 1

You don't need a temp var when using a tuple:

def fib() = {
  var t = (1,-1)
  () => { 
    t = (t._1 + t._2, t._1)
    t._1
  }
}

But in real life you should use Apocalisp's solution.