+ redef fun iterator: ArrayIterator[E] do
+ var res = _free_iterator
+ if res == null then return new ArrayIterator[E](self)
+ res._index = 0
+ _free_iterator = null
+ return res
+ end
+
+ # An old iterator, free to reuse.
+ # Once an iterator is `finish`, it become reusable.
+ # Since some arrays are iterated a lot, this avoid most of the
+ # continuous allocation/garbage-collection of the needed iterators.
+ private var free_iterator: nullable ArrayIterator[E] = null
+