default int[] next() {
		final var index = new int[size()];
		return next(index) ? index : null;
	}
Return the next index value or {@code null} if no further value is
available.
{@snippet class="CombinatorialSnippets" region="Cursor.loop2"}

@return the next element or {@code null} if no further value is available
jenetics.incubator/src/main/java/io/jenetics/incubator/combinatorial/Cursor.java