Insertion sort imperative and functional

InsertionSort.scala

/**
  * Created by vincentdupont on 26/8/16.
  */

import util.Random

object InsertionSort extends App {
  def sortImp(a: Array[Int]) : Array[Int] = {
    var key, i : Int = 0
    for (j <- 1 until a.length) {
      key = a(j)
      i = j-1
      while (i >= 0 && a(i) > key) {
        a(i+1) = a(i)
        i -= 1
      }
      a(i+1) = key
    }
    a
  }
  var randomArray = Seq.fill(6)(Random.nextInt(100)).toArray
  assert(sortImp(randomArray) sameElements randomArray.sorted)

  def sortFun(a: List[Int]) : List[Int] = {

    def insert(b: List[Int]) : List[Int] = b match {
      case Nil => List(a.head)
      case y::ys => if (a.head < y) a.head :: y :: ys else y :: insert(ys)
    }

    a match {
      case Nil => Nil
      case x::Nil => List(x)
      case x::xs => insert(sortFun(xs))
    }

  }

  assert(sortFun(List()) == Nil)
  assert(sortFun(List(5)) == List(5))
  val randomList = Seq.fill(6)(Random.nextInt(100)).toList
  assert(sortFun(randomList) equals randomList.sorted)

}