Example of open recursion: add a new object type into a low-level language run time. You implement a garbage traversal routine for it, which recurses over trav

Example of open recursion: add a new object type into a low-level language run time. You implement a garbage traversal routine for it, which recurses over traversing the child objects. The system is open to extension; the garbage collector doesn't just have a switch statement to handle all the known objects. It may have that too, but for some object kinds, it dispatches their method.