isOrder.scala

def isSorted[A](as: Array[A], gt: (A,A) => Boolean): Boolean = {
  @annotation.tailrec
  def loop(n:Int) : Boolean =
    if (n >= as.length - 1)          true
    else if (gt(as(n), as(n+1))) loop(n+1)
    else                             false
  loop(0)
}

println(isSorted[Int](Array(1,2,3), _<_))
println(isSorted[Int](Array(3,1,2), _<_))
println(isSorted[Int](Array(), _<_))
println(isSorted[Int](Array(1), _<_))