Inheritance and Specialization of Methods and Functions

Method Inheritance with shapes Here's an example of inheritance and specialization using methods

define SHAPE:  				// abstract - no attributes
       method:area()			// one method with no implementation - all shapes have area
define SQUARE < SHAPE			// square is a subclass of shape
       side number			// with attribute side
       method:area() = side * side	// and area side * side
define CIRCLE < SHAPE			// circle is a subclass of shape
       radius number			// it has one attribute radius
       method:area() = pi * radius**2	// it specializes the area method

let s1 = SQUARE.new(side=5)             // create a square
let c1 = CIRCLE.new(radius=3)           // create a circle
let shapes = {s1,c1}  			// a collection of two different shape subclasses
for s in shapes                         // for every shape
    if s.area() > 10 then message end   // find their areas
end

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How would this be accomplished with functions?

Does this approach make sense?

Functions not defined as part of a class, but arguments may be instances of the classes)

function:area(SHAPE)				  // this doesn't seem necessary
function:area(SQUARE) = square.side * square.side // defines area for a square
function:area(CIRCLE) = pi * circle.radius**2	  // defines area for a cicle
// basically area is an overloaded function in this example

define SHAPE:  					// abstract - no attributes
define SQUARE < SHAPE				// square is a subclass of shape
       side number				// with attribute side
define CIRCLE < SHAPE				// circle is a subclass of shape
       radius number				// it has one attribute radius

let s1 = SQUARE.new(side=5)                     // create a square
let c1 = CIRCLE.new(radius=3)                   // create a circle
let shapes = {s1,c1}  				// a collection of two different shape subclasses
for s in shapes                                 // for every shape
    if area(s) > 10 then message end            // find the area
end