Polymorphism: Difference between revisions

 

Create two classes Point(x,y) and Circle(x,y,r) with a polymorphic function print, accessors for (x,y,r), copy constructor, assignment and destructor and every possible default constructors

This example is constructed using a parent package and a child package. The parent package defines the Point type. The child package defines the Circle type.

 

 

 

* See [[Polymorphism (BASIC)]]

 

* See [[Polymorphism (C)]]

 

}

 

using System;

class Point

}

 

(defclass point ()

((x :initarg :x :initform 0 :accessor x)

(print-shape c))

 

def makePoint(x, y) {

def point implements pbc {

println(c)

 

Polymorhism is achieved through the type class Show

 

}

 

class point ?(x=0.0) ?(y=0.0) () = (* extra () used to erase the optional parameters *)

object

print (new point ~y:2.1 ())

 

What polymorphic function means in the context of Perl is as clear as mud. subs already can take anything as parameter by default. Destructors are automatic, so I dropped them.

{

};

 

When class is defined in Pop11 it automatically defines default

constructors, slot accessors and copy operations. So it is enough

print(instance2);

 

Multiple constructors are not needed because Python supports default values for arguments. Accessors are not needed because Python attributes are public. It is possible to add managed attributes later without changing the interface and existing client code. For the print function, use the standard __repr__ methods, used when printing an object. Destructors are not needed of course.

 

</pre>

 

We use attr_accessor to provide all the accessor and assignment operations. Default arguments eliminate the need for multiple constructors. The built-in puts uses the object's to_s method.