# Wraps an iterator to skip nulls.
#
# ~~~nit
# var i: Iterator[Int]
#
# i = new NullSkipper[Int]([null, 1, null, 2, null: nullable Int].iterator)
# assert i.to_a == [1, 2]
#
# i = new NullSkipper[Int]([1, null, 2, 3: nullable Int].iterator)
# assert i.to_a == [1, 2, 3]
# ~~~
class NullSkipper[E: Object]
	super Iterator[E]

	# The inner iterator.
	var inner: Iterator[nullable E]

	redef fun finish do inner.finish

	redef fun is_ok do
		skip_nulls
		return inner.is_ok
	end

	redef fun item do
		skip_nulls
		return inner.item.as(E)
	end

	redef fun next do
		inner.next
		skip_nulls
	end

	private fun skip_nulls do
		while inner.is_ok and inner.item == null do inner.next
	end
end