Example of tail-recursion in Scala that will not throw a StackOverflowError.

Scala Loop-Recur for zipper

// Scala analog to Clojure's loop-recur construct
def loopRecur[A](index: Int, coll: Seq[A], zippedList: List[(Int, A)]): List[(Int, A)] = {
    if (coll.isEmpty) return zippedList
    else return loopRecur(index + 1, coll.tail, zippedList ++ List((index, coll.head)))
}

// Given a sequecne of items, returns a List of tuples of the form (item index, item)
def zipIndex[A](coll: Seq[A]): List[(Int, A)] = {
    return loopRecur(0, coll, List.empty[(Int, A)])
}