+
+ # Returns a sub-array containing `count` elements starting from `from`.
+ #
+ # For most cases (see other case bellow),
+ # the first element is `from` and
+ # the last element is `from+count-1`.
+ #
+ # ~~~
+ # var a = [10, 20, 30, 40, 50]
+ # assert a.sub(0, 3) == [10, 20, 30]
+ # assert a.sub(3, 2) == [40, 50]
+ # assert a.sub(3, 1) == [40]
+ # ~~~
+ #
+ # If `count` is 0 or negative then an empty array is returned
+ #
+ # ~~~
+ # assert a.sub(3,0).is_empty
+ # assert a.sub(3,-1).is_empty
+ # ~~~
+ #
+ # If `from < 0` or `from+count>length` then inexistent elements are ignored.
+ # In this case the length of the result is lower than count.
+ #
+ # ~~~
+ # assert a.sub(-2, 4) == [10, 20]
+ # assert a.sub(4, 99) == [50]
+ # assert a.sub(-9, 99) == [10,20,30,40,50]
+ # assert a.sub(-99, 9).is_empty
+ # ~~~
+ fun sub(from: Int, count: Int): Array[E] do
+ if from < 0 then
+ count += from
+ from = 0
+ end
+ if count < 0 then
+ count = 0
+ end
+ var to = from + count
+ if to > length then
+ to = length
+ end
+ var res = new Array[E].with_capacity(to - from)
+ while from < to do
+ res.add(self[from])
+ from += 1
+ end
+ return res
+ end