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We want to implement Iterators in Funnel. The following definition
describes the abstract Iterator class:
abstract class Iterator = {
abstract def next
abstract def hasNext
def toList = ...
def toString = ...
}
A ListIterator inherits from Iterator and defines the two abstract
methods next and hasNext:
final class ListIterator(xs) extends Iterator = {
def next = ...
def hasNext = ...
}
The ListIterator class is final, so subclassing should not be
possible. Implement the Iterator and ListIterator classes in Funnel.
Here's a framework:
import "List.fn"
import "Predef.fn"
type ConcreteIterator = (toList, toString)
type Iterator = (with ConcreteIterator, next, hasNext)
val Iterator = {
...
}
val ListIterator = {
...
}
// execute some example code
val xs = List.make5(2, 4, 6, 8, 9)
ListIterator.new(xs).toString
