foldLeft.kt

fun main(args : Array<String>) {
  val arr = array(1, 2, 3)
  println(foldLeft(0, arr, {x, y -> x + y}))
}

fun foldLeft<A, B>(z: B, array: Array<A>, f: (A, B) -> B): B {
  
  [tailRecursive] fun go(i: Int, z: B) =
    if (i == array.size()) z
    else go(i + 1, f(array.get(i), z)) 
                  
  return go(0, z)
}