Fibonacci in Scala

fib.scala

def fib(p: Int): List[Int] = {
  def recFib(list: List[Int], len: Int): List[Int] = {
    if (len == 0) {
      list
    } else {
      list match {
        case n :: n_1 :: _ => recFib(n + n_1 :: list, len -1)
        case _ => recFib(1 :: list, len -1)
      }
    }
  }
  recFib(List(0), p).reverse
}

fib(1) == List(0, 1)
fib(2) == List(0, 1, 1)
fib(3) == List(0, 1, 1, 2)
fib(4) == List(0, 1, 1, 2, 3)
fib(5) == List(0, 1, 1, 2, 3, 5)

fib(45)