scheme representation of objects
how objects are represented in the problem set
- an object O is represented by a chain of Scheme closures, one for each class in the path upwards in the inheritance hierarchy
- each subclass closure contains a pointer to its superclass closure
- each closure has a self pointer that always points to the object O
confusing terminology
- the superclass closure is said to be a “part” of the subclass closure
- but not a part in the modelling sense: Vehicle is a part of Car, Wheel is not a part of Car!
how parts differ from objects
- their self pointers don’t point to themselves
- each is accessible only to the one closure that contains it