I'm still learning Scala so this may be very wrong for a number of reasons. I'm not even sure about the meaning of the <: operator

tailrecmaxcomparable

  // for: http://stackoverflow.com/questions/14011181/how-can-i-find-the-index-of-the-maximum-value-in-a-list-in-scala

  @tailrec
  final def maxindex[T <: Ordered[T]](list:Iterable[T], defaultIndex:Int = -1, defaultValue:T=None, currentIndex:Int = 0):(Int, T) = list match { 
    case Nil => (defaultIndex, defaultValue)
    case head::tail =>
      if (head > defaultValue)
        maxindex(tail, currentIndex, head, currentIndex+1)
      else
        maxindex(tail, defaultIndex, defaultValue, currentIndex+1)
  }