Xlisp Object Terminology

There are, as previously mentioned, many different languages with object-oriented extensions and facilities. The terminology, operations and styles of these are very different. Some of the main definitions for XLISP's object-oriented extensions are:

Object data type

The OBJECT DATA TYPE is a built-in data type of XLISP. Members of the object data type are object instances and classes.

Object instances

An OBJECT INSTANCE is a composite structure that contains internal state information, methods (the code which respond to messages), a pointer to the object instance's defining class and a pointer to the object's super-class. XLISP contains no built-in object instances.

Class objects

A CLASS OBJECT is, essentially, the template for defining the derived object instances. A class object, although used differently from a simple object instance, is structurally a member of the object data type. It is also contains the linking mechanism that allows you to build class hierarchies (sub-classes and super-classes). XLISP contains two built-in class objects: OBJECT and CLASS.

Message selector

The MESSAGE SELECTOR is the symbol that is used to select a particular action (Method) from the object.

Message

The MESSAGE is the combination of the message selector and the data (if any) to be sent to the object.

Method

The METHOD is the actual code that gets executed when the object receives the Message.