private class CartesianIterator[E]
	super Iterator[SequenceRead[E]]
	var collection: CartesianCollection[E]

	# The array of iterations that will be increased in the lexicographic order.
	var iterators = new Array[Iterator[E]]

	init
	do
		for c in collection.collections do
			var it = c.iterator
			iterators.add it
			if not it.is_ok then is_ok = false
		end
	end

	redef var is_ok = true

	redef fun item
	do
		var len = iterators.length
		var res = new Array[E].with_capacity(len)
		for i in [0..len[ do
			var it = iterators[i]
			res.add(it.item)
		end
		return res
	end

	redef fun next
	do
		var rank = iterators.length - 1

		# Odometer-like increment starting from the last iterator
		loop
			var it = iterators[rank]
			it.next
			if it.is_ok then return

			# The iterator if over
			if rank == 0 then
				# It it is the first, then the whole thing is over
				is_ok = false
				return
			end

			# If not, restart the iterator and increment the previous one
			# (like a carry)
			iterators[rank] = collection.collections[rank].iterator
			rank -= 1
		end
	end
end