* int_stack.nit: simple class for a stack of integers implemented with a linked list.
* clock_more.nit: refine clock to add comparability between clocks.
* circular_list.nit: simple use of generic classes and nullable types to implement a double-linked circular list.
* int_stack.nit: simple class for a stack of integers implemented with a linked list.
* clock_more.nit: refine clock to add comparability between clocks.
* circular_list.nit: simple use of generic classes and nullable types to implement a double-linked circular list.