Marvin3 and Object Orientation

Marvin3 supports object-oriented programming through the use of classes. Inheritance is not supported at the moment but it will surely be added in the later stages of the development.

To declare a class you use @ symbol.

    @class-name
        [constructing code] [me]
        :method1-name [method2 code] ;
        :method2-name [method2 code] ;
    ;

For example, consider the following 2D point class

    @Point
        !y !x  me
        :x %x ;  
        :y %y ; 
        :distance lhs .x %x - sqr lhs .y %y - sqr sqrt ; 
    ;

To instantiate a Point

    5 10 Point !point-a  # create a point at(5,10)
    42 4 Point !point-b  # create a point at (42,4)
    %point-a %point-b .distance println

Marvin3 classes have the following properties:

• All data is private, all methods are public
• The constructor is not a special method as it is in many languages(e.g., Python's __init__), it is the body of the class.
• In class, use me keyword to access to the instance (just like C++'s this or Object Pascal's self)
• If you want your class to leave the instance on the stack, you must push the instance on the stack by calling me in the body.
• To create a new member variable or modify an existing one, simply popto (e.g., !y). To read one, pushfrom (e.g., %y)
• You can read the values of global variables, if they are not shadowed by a member variable
• You can access methods inside a class by, me .method-name
• You can instantiate a class by simply calling it
• A method of an object can be called by .method-name if the object is on the stack