sort.scala

def isSorted[A](as: Array[A], ordered: (A,A) => Boolean): Boolean = {
  if (as.length <= 1) true
  else {
    @annotation.tailrec
    def checkSort(n: Int): Boolean = {
      if (n >= as.length) true
      else if (!ordered(as(n - 1), as(n))) false
      else checkSort(n+1)
    }

    checkSort(1)
  }
}