FibonacciBinet.scala

object FibonacciBinet {

  def fib(n: Int) = {
    def A = Math.pow(1 + Math.sqrt(5), n)
    def B = Math.pow(1 - Math.sqrt(5), n)
    def C = Math.pow(2, n) * Math.sqrt(5)

    Math.floor((A - B) / C)
  }

  fib(0)
  fib(1)
  fib(2)
  fib(3)
  fib(4)
  fib(12)
}