Polymorphism

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Task
Polymorphism
You are encouraged to solve this task according to the task description, using any language you may know.
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

Contents

[edit] ActionScript

package
{
public class Point
{
protected var _x:Number;
protected var _y:Number;
 
public function Point(x:Number = 0, y:Number = 0)
{
_x = x;
_y = y;
}
 
public function getX():Number
{
return _x;
}
 
public function setX(x:Number):void
{
_x = x;
}
 
public function getY():Number
{
return _y;
}
 
public function setY(y:Number):void
{
_x = y;
}
 
public function print():void
{
trace("Point");
}
}
}
package {
public class Circle extends Point
{
private var r:Number;
 
public function Circle(x:Number=0, y:Number=0, r:Number=0)
{
super(x, y);
this.r = r;
}
 
public function getR():Number
{
return r;
}
 
public function setR(r:Number):void
{
this.r = r;
}
 
public override function print():void
{
trace("Circle");
}
}
}

[edit] Ada

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.

package Shapes is
type Point is tagged private;
procedure Print(Item : in Point);
function Setx(Item : in Point; Val : Integer) return Point;
function Sety(Item : in Point; Val : Integer) return Point;
function Getx(Item : in Point) return Integer;
function Gety(Item : in Point) return Integer;
function Create return Point;
function Create(X : Integer) return Point;
function Create(X, Y : Integer) return Point;
 
private
type Point is tagged record
X : Integer := 0;
Y : Integer := 0;
end record;
end Shapes;
with Ada.Text_Io; use Ada.Text_Io;
 
package body Shapes is
 
-----------
-- Print --
-----------
 
procedure Print (Item : in Point) is
begin
Put_line("Point");
end Print;
 
----------
-- Setx --
----------
 
function Setx (Item : in Point; Val : Integer) return Point is
begin
return (Val, Item.Y);
end Setx;
 
----------
-- Sety --
----------
 
function Sety (Item : in Point; Val : Integer) return Point is
begin
return (Item.X, Val);
end Sety;
 
----------
-- Getx --
----------
 
function Getx (Item : in Point) return Integer is
begin
return Item.X;
end Getx;
 
----------
-- Gety --
----------
 
function Gety (Item : in Point) return Integer is
begin
return Item.Y;
end Gety;
 
------------
-- Create --
------------
 
function Create return Point is
begin
return (0, 0);
end Create;
 
------------
-- Create --
------------
 
function Create (X : Integer) return Point is
begin
return (X, 0);
end Create;
 
------------
-- Create --
------------
 
function Create (X, Y : Integer) return Point is
begin
return (X, Y);
end Create;
 
end Shapes;

The following is the child package defining the Circle type.

package Shapes.Circles is
type Circle is new Point with private;
procedure Print(Item : Circle);
function Setx(Item : Circle; Val : Integer) return Circle;
function Sety(Item : Circle; Val : Integer) return Circle;
function Setr(Item : Circle; Val : Integer) return Circle;
function Getr(Item : Circle) return Integer;
function Create(P : Point) return Circle;
function Create(P : Point; R : Integer) return Circle;
function Create(X : Integer) return Circle;
function Create(X : Integer; Y : Integer) return Circle;
function Create(X : Integer; Y : Integer; R : Integer) return Circle;
function Create return Circle;
private
type Circle is new Point with record
R : Integer := 0;
end record;
end Shapes.Circles;
with Ada.Text_Io; use Ada.Text_IO;
 
package body Shapes.Circles is
 
-----------
-- Print --
-----------
 
procedure Print (Item : Circle) is
begin
Put_line("Circle");
end Print;
 
----------
-- Setx --
----------
 
function Setx (Item : Circle; Val : Integer) return Circle is
begin
return (Val, Item.Y, Item.R);
end Setx;
 
----------
-- Sety --
----------
 
function Sety (Item : Circle; Val : Integer) return Circle is
Temp : Circle := Item;
begin
Temp.Y := Val;
return Temp;
end Sety;
 
----------
-- Setr --
----------
 
function Setr (Item : Circle; Val : Integer) return Circle is
begin
return (Item.X, Item.Y, Val);
end Setr;
 
----------
-- Getr --
----------
 
function Getr (Item : Circle) return Integer is
begin
return Item.R;
end Getr;
 
------------
-- Create --
------------
 
function Create (P : Point) return Circle is
begin
return (P.X, P.Y, 0);
end Create;
 
------------
-- Create --
------------
 
function Create (P : Point; R : Integer) return Circle is
begin
return (P.X, P.Y, R);
end Create;
 
------------
-- Create --
------------
 
function Create (X : Integer) return Circle is
begin
return (X, 0, 0);
end Create;
 
------------
-- Create --
------------
 
function Create (X : Integer; Y : Integer) return Circle is
begin
return (X, Y, 0);
end Create;
 
------------
-- Create --
------------
 
function Create (X : Integer; Y : Integer; R : Integer) return Circle is
begin
return (X, Y, R);
end Create;
 
------------
-- Create --
------------
 
function Create return Circle is
begin
return (0, 0, 0);
end Create;
 
end Shapes.Circles;

The following procedure is an entry point for a program, serving the same purpose as the main function in C.

with Shapes.Circles; use Shapes.Circles;
use Shapes;
 
procedure Shapes_Main is
P : Point;
C : Circle;
begin
P.Print;
C.Print;
end Shapes_Main;

[edit] Aikido

 
class Point (protected x=0.0, protected y=0.0) {
public function print {
println ("Point")
}
 
public function getX { return x }
public function getY { return y }
 
public function setX(nx) { x = nx }
public function setY(ny) { y = ny }
}
 
class Circle (x=0.0, y=0.0, r=0.0) extends Point (x, y) {
public function print {
println ("Circle")
}
 
public function getR { return r }
public function setR(nr) { r = nr }
}
 
var p = new Point (1, 2)
var c = new Circle (1, 2, 3)
p.print()
c.print()
 
 

[edit] AutoHotkey

Works with: AutoHotkey 1.1

AutoHotkey does not support private or protected properties and thus does not need assignment and accessor methods. Assignment and accessor methods, as well as direct assignment and access, are shown. For more information see Objects.

MyPoint := new Point(1, 8)
MyPoint.Print()
MyCircle := new Circle(4, 7, 9)
MyCircle2 := MyCircle.Copy()
MyCircle.SetX(2) ;Assignment method
MyCircle.y := 3 ;Direct assignment
MyCircle.Print()
MyCircle2.Print()
MyCircle.SetX(100), MyCircle.SetY(1000), MyCircle.r := 10000
MsgBox, % MyCircle.__Class
. "`n`nx:`t" MyCircle.GetX()
. "`ny:`t" MyCircle.y
. "`nr:`t" MyCircle.GetR()
return
 
class Point
{
Copy()
{
return this.Clone()
}
GetX()
{
return this.x
}
GetY()
{
return this.y
}
__New(x, y)
{
this.x := x
this.y := y
}
Print()
{
MsgBox, % this.__Class
. "`n`nx:`t" this.x
. "`ny:`t" this.y
}
SetX(aValue)
{
this.x := aValue
}
SetY(aValue)
{
this.y := aValue
}
}
 
class Circle extends Point
{
GetR()
{
return this.r
}
__New(x, y, r)
{
this.r := r
base.__New(x, y)
}
Print()
{
MsgBox, % this.__Class
. "`n`nx:`t" this.x
. "`ny:`t" this.y
. "`nr:`t" this.r
}
SetR(aValue)
{
this.r := aValue
}
}

[edit] BASIC

[edit] BBC BASIC

      INSTALL @lib$ + "CLASSLIB"
 
REM Create parent class with void 'doprint' method:
DIM PrintableShape{doprint}
PROC_class(PrintableShape{})
 
REM Create derived class for Point:
DIM Point{x#, y#, setxy, retx, rety, @constructor, @@destructor}
PROC_inherit(Point{}, PrintableShape{})
DEF Point.setxy (x,y) : Point.x# = x : Point.y# = y : ENDPROC
DEF Point.retx = Point.x#
DEF Point.rety = Point.y#
DEF Point.@constructor Point.x# = 1.23 : Point.y# = 4.56 : ENDPROC
DEF Point.@@destructor : ENDPROC
DEF Point.doprint : PRINT Point.x#, Point.y# : ENDPROC
PROC_class(Point{})
 
REM Create derived class for Circle:
DIM Circle{x#, y#, r#, setxy, setr, retx, rety, retr, @con, @@des}
PROC_inherit(Circle{}, PrintableShape{})
DEF Circle.setxy (x,y) : Circle.x# = x : Circle.y# = y : ENDPROC
DEF Circle.setr (r) : Circle.r# = r : ENDPROC
DEF Circle.retx = Circle.x#
DEF Circle.rety = Circle.y#
DEF Circle.retr = Circle.r#
DEF Circle.@con Circle.x# = 3.2 : Circle.y# = 6.5 : Circle.r# = 7 : ENDPROC
DEF Circle.@@des : ENDPROC
DEF Circle.doprint : PRINT Circle.x#, Circle.y#, Circle.r# : ENDPROC
PROC_class(Circle{})
 
REM Test the polymorphic 'doprint' function:
PROC_new(mypoint{}, Point{})
PROC(mypoint.doprint)
PROC_discard(mypoint{})
PROC_new(mycircle{}, Circle{})
PROC(mycircle.doprint)
PROC_discard(mycircle{})
END

Output:

      1.23      4.56
       3.2       6.5         7

[edit] C

[edit] C++

class Point
{
protected:
int x, y;
public:
Point(int x0 = 0, int y0 = 0) : x(x0), y(y0) {}
Point(const Point& p) : x(p.x), y(p.y) {}
virtual ~Point() {}
const Point& operator=(const Point& p)
{
if(this != &p)
{
x = p.x;
y = p.y;
}
return *this;
}
int getX() { return x; }
int getY() { return y; }
int setX(int x0) { x = x0; }
int setY(int y0) { y = y0; }
virtual void print() { printf("Point\n"); }
};
 
class Circle : public Point
{
private:
int r;
public:
Circle(Point p, int r0 = 0) : Point(p), r(r0) {}
Circle(int x0 = 0, int y0 = 0, int r0 = 0) : Point(x0, y0), r(r0) {}
virtual ~Circle() {}
const Circle& operator=(const Circle& c)
{
if(this != &c)
{
x = c.x;
y = c.y;
r = c.r;
}
return *this;
}
int getR() { return r; }
int setR(int r0) { r = r0; }
virtual void print() { printf("Circle\n"); }
};
 
int main()
{
Point* p = new Point();
Point* c = new Circle();
p->print();
c->print();
return 0;
}

Pattern: Curiously Recurring Template Pattern

// CRTP: Curiously Recurring Template Pattern
template <typename Derived>
class PointShape
{
protected:
int x, y;
public:
PointShape(int x0, int y0) : x(x0), y(y0) { }
~PointShape() { }
int getX() { return x; }
int getY() { return y; }
int setX(int x0) { x = x0; }
int setY(int y0) { y = y0; }
 
// compile-time virtual function
void print() { reinterpret_cast<const Derived*>(this)->printType(); }
};
 
class Point : public PointShape<Point>
{
public:
Point(int x0 = 0, int y0 = 0) : PointShape(x0, y0) { }
Point(const Point& p) : PointShape(p.x, p.y) { }
~Point() {}
const Point& operator=(const Point& p)
{
if(this != &p)
{
x = p.x;
y = p.y;
}
return *this;
}
void printType() { printf("Point\n"); }
};
 
class Circle : public PointShape<Circle>
{
private:
int r;
public:
Circle(int x0 = 0, int y0 = 0, int r0 = 0) : PointShape(x0, y0), r(r0) { }
Circle(Point p, int r0 = 0) : PointShape(p.x, p.y), r(r0) { }
~Circle() {}
const Circle& operator=(const Circle& c)
{
if(this != &c)
{
x = c.x;
y = c.y;
r = c.r;
}
return *this;
}
int getR() { return r; }
int setR(int r0) { r = r0; }
void printType() { printf("Circle\n"); }
};
 
int main()
{
Point* p = new Point();
Point* c = new Circle();
p->print();
c->print();
return 0;
}

[edit] C#

using System;
class Point
{
protected int x, y;
public Point() : this(0) {}
public Point(int x) : this(x,0) {}
public Point(int x, int y) { this.x = x; this.y = y; }
public int X { get { return x; } set { x = value; } }
public int Y { get { return y; } set { y = value; } }
public virtual void print() { System.Console.WriteLine("Point"); }
}
 
public class Circle : Point
{
private int r;
public Circle(Point p) : this(p,0) { }
public Circle(Point p, int r) : base(p) { this.r = r; }
public Circle() : this(0) { }
public Circle(int x) : this(x,0) { }
public Circle(int x, int y) : this(x,y,0) { }
public Circle(int x, int y, int r) : base(x,y) { this.r = r; }
public int R { get { return r; } set { r = value; } }
public override void print() { System.Console.WriteLine("Circle"); }
 
public static void main(String args[])
{
Point p = new Point();
Point c = new Circle();
p.print();
c.print();
}
}

[edit] Clojure

Clojure 1.2.

(defprotocol Printable 
(print-it [this] "Prints out the Printable."))
 
(deftype Point [x y]
Printable
(print-it [this] (println (str "Point: " x " " y))))
 
(defn create-point
"Redundant constructor function."
[x y] (Point. x y))
 
(deftype Circle [x y r]
Printable
(print-it [this] (println (str "Circle: " x " " y " " r))))
 
(defn create-circle
"Redundant consturctor function."
[x y r] (Circle. x y r))

[edit] Common Lisp

(defclass point ()
((x :initarg :x :initform 0 :accessor x)
(y :initarg :y :initform 0 :accessor y)))
 
(defclass circle (point)
((radius :initarg :radius :initform 0 :accessor radius)))
 
(defgeneric shallow-copy (object))
(defmethod shallow-copy ((p point))
(make-instance 'point :x (x p) :y (y p)))
(defmethod shallow-copy ((c circle))
(make-instance 'circle :x (x c) :y (y c) :radius (radius c)))
 
(defgeneric print-shape (shape))
(defmethod print-shape ((p point))
(print 'point))
(defmethod print-shape ((c circle))
(print 'circle))
 
(let ((p (make-instance 'point :x 10))
(c (make-instance 'circle :radius 5)))
(print-shape p)
(print-shape c))

[edit] D

import std.stdio: writeln;
 
class Point {
private int x, y;
this(int x_=0, int y_=0) { x = x_; y = y_; }
this(Point p_) { x = p_.getX(); y = p_.getY(); }
int getX() { return x; }
void setX(int x_) { this.x = x_; }
int getY() { return y; }
void setY(int y_) { this.y = y_; }
}
 
class Circle : Point {
private int r;
this(int x_=0, int y_=0, int r_=0) {
super(x_, y_);
r = r_;
}
this(Point p, int r_=0) {
super(p);
r = r_;
}
this(Circle c_) {
super(c_.getX(), c_.getY());
r = c_.getR();
}
int getR() { return r; }
void setR(int r0) { this.r = r0; }
}
 
void main() {
auto p = new Point();
auto c = new Circle();
writeln(p);
writeln(c);
}

[edit] Delphi

type
{ TPoint }
 
TMyPoint = class
private
FX: Integer;
FY: Integer;
public
constructor Create; overload;
constructor Create(X0: Integer; Y0: Integer); overload;
constructor Create(MyPoint: TMyPoint); overload;
destructor Destroy; override;
 
procedure Print; virtual;
 
property X: Integer read FX write FX;
property Y: Integer read FY write FY;
end;
 
{ TCircle }
 
TCircle = class(TMyPoint)
private
FR: Integer;
public
constructor Create(X0: Integer; Y0: Integer; R0: Integer); overload;
constructor Create(MyPoint: TMyPoint; R0: Integer); overload;
constructor Create(Circle: TCircle); overload;
destructor Destroy; override;
 
procedure Print; override;
 
property R: Integer read FR write FR;
end;
 
implementation
 
uses Dialogs;
 
{ TCircle }
 
constructor TCircle.Create(X0: Integer; Y0: Integer; R0: Integer);
begin
inherited Create(X0, Y0);
FR := R0;
end;
 
constructor TCircle.Create(MyPoint: TMyPoint; R0: Integer);
begin
inherited Create(MyPoint);
FR := R0;
end;
 
constructor TCircle.Create(Circle: TCircle);
begin
Create;
if not(Circle = Self) then
begin
FX := Circle.X;
FY := Circle.Y;
FR := Circle.R;
end;
end;
 
destructor TCircle.Destroy;
begin
inherited Destroy;
end;
 
procedure TCircle.Print;
begin
ShowMessage('Circle');
end;
 
{ TMyPoint }
 
constructor TMyPoint.Create;
begin
inherited Create;
end;
 
constructor TMyPoint.Create(X0: Integer; Y0: Integer);
begin
Create;
FX := X0;
FY := Y0;
end;
 
constructor TMyPoint.Create(MyPoint: TMyPoint);
begin
Create;
if not(MyPoint = Self) then
begin
FX := MyPoint.X;
FY := MyPoint.Y;
end;
end;
 
destructor TMyPoint.Destroy;
begin
inherited Destroy;
end;
 
procedure TMyPoint.Print;
begin
ShowMessage('MyPoint');
end;
var
MyPoint: TMyPoint;
Circle: TCircle;
begin
MyPoint := TMyPoint.Create;
try
MyPoint.Print;
Circle := TCircle.Create;
try
Circle.Print;
finally
FreeAndNil(Circle);
end;
finally
FreeAndNil(MyPoint);
end;
end;

[edit] E

def makePoint(x, y) {
def point implements pbc {
to __printOn(out) { out.print(`<point $x,$y>`) }
to __optUncall() { return [makePoint, "run", [x, y]] }
to x() { return x }
to y() { return y }
to withX(new) { return makePoint(new, y) }
to withY(new) { return makePoint(x, new) }
}
return point
}
 
def makeCircle(x, y, r) {
def circle extends makePoint(x, y) implements pbc {
to __printOn(out) { out.print(`<circle $x,$y r $r>`) }
to __optUncall() { return [makeCircle, "run", [x, y, r]] }
to r() { return r }
to withX(new) { return makeCircle(new, y, r) }
to withY(new) { return makeCircle(x, new, r) }
to withR(new) { return makeCircle(x, y, new) }
}
return circle
}

(It is unidiomatic to have mutation operations on an object of this sort in E, so this example has variation operations instead. __optUncall is used for serialization, and is the closest analogue to a copy constructor. E does not have destructors, but only post-mortem finalizers (which are registered after the object is created). The "extends" is only implementation inheritance; it is not necessary to enable polymorphism.)

def p := makePoint(0.5, 0.5)
def c := makeCircle(1, 1, 2)
println(p)
println(c)

[edit] Eiffel

class
POINT
inherit
ANY
redefine
out
end
create
make, make_origin
 
feature -- Initialization
 
make (a_x, a_y: INTEGER)
-- Create with values `a_x' and `a_y'
do
set_x (a_x)
set_y (a_y)
ensure
x_set: x = a_x
y_set: y = a_y
end
 
make_origin
-- Create at origin
do
ensure
x_set: x = 0
y_set: y = 0
end
 
feature -- Access
 
x: INTEGER assign set_x
-- Horizontal axis coordinate
 
y: INTEGER assign set_y
-- Vertical axis coordinate
 
feature -- Element change
 
set_x (a_x: INTEGER)
-- Set `x' coordinate to `a_x'
do
x := a_x
ensure
x_set: x = a_x
end
 
set_y (a_y: INTEGER)
-- Set `y' coordinate to `a_y'
do
y := a_y
ensure
y_set: y = a_y
end
 
feature -- Output
 
out: STRING
-- Display as string
do
Result := "Point: x = " + x.out + " y = " + y.out
end
end


class
CIRCLE
 
inherit
POINT
rename
make as point_make
redefine
make_origin,
out
end
create
make, make_origin, make_from_point
 
feature -- Initialization
 
make (a_x, a_y, a_r: INTEGER)
-- Create with values `a_x' and `a_y' and `a_r'
require
non_negative_radius_argument: a_r >= 0
do
point_make (a_x, a_y)
set_r (a_r)
ensure
x_set: x = a_x
y_set: y = a_y
r_set: r = a_r
end
 
make_origin
-- Create at origin with zero radius
do
Precursor
ensure then
r_set: r = 0
end
 
make_from_point (a_p: POINT; a_r: INTEGER)
-- Initialize from `a_r' with radius `a_r'.
require
non_negative_radius_argument: a_r >= 0
do
set_x (a_p.x)
set_y (a_p.y)
set_r (a_r)
ensure
x_set: x = a_p.x
y_set: y = a_p.y
r_set: r = a_r
end
 
feature -- Access
 
r: INTEGER assign set_r
-- Radius
 
feature -- Element change
 
set_r (a_r: INTEGER)
-- Set radius (`r') to `a_r'
require
non_negative_radius_argument: a_r >= 0
do
r := a_r
ensure
r_set: r = a_r
end
 
feature -- Output
 
out: STRING
-- Display as string
do
Result := "Circle: x = " + x.out + " y = " + y.out + " r = " + r.out
end
 
invariant
 
non_negative_radius: r >= 0
 
end


class
APPLICATION
 
create
make
 
feature {NONE} -- Initialization
 
make
-- Run application.
local
my_point: POINT
my_circle: CIRCLE
do
create my_point.make_origin
print (my_point.out + "%N")
 
create {CIRCLE} my_point.make_origin
print (my_point.out + "%N")
 
create my_point.make (10, 15)
print (my_point.out + "%N")
 
create {CIRCLE} my_point.make (20, 25, 5)
print (my_point.out + "%N")
 
create my_circle.make (30, 35, 10)
print (my_circle.out + "%N")
 
create my_circle.make_from_point (my_point, 35)
print (my_circle.out + "%N")
end
 
end

Output:

 
Point: x = 0 y = 0
Circle: x = 0 y = 0 r = 0
Point: x = 10 y = 15
Circle: x = 20 y = 25 r = 5
Circle: x = 30 y = 35 r = 10
Circle: x = 20 y = 25 r = 35
 

Notes:

The Eiffel example varies slightly from the problem description. The polymorphic feature is out rather than print. Both out and print are inherited by every Eiffel class from class ANY. However, it is customary in Eiffel to redefine the query out to provide a string describing an instance, versus redefining print. So, this example is written to reflect the Eiffel convention.

[edit] Ela

Solution of this problem in Ela is similar to Haskell, as soon as Ela shares with Haskell the same features - namely, classes (typeclasses) and algebraic types.

type Point = Point x y
 
instance Show Point where
showf _ (Point x y) = "Point " ++ (show x) ++ " " ++ (show y)
 
instance Name Point where
getField nm (Point x y)
| nm == "x" = x
| nm == "y" = y
| else = fail "Undefined name."
isField nm _ = nm == "x" or nm == "y"
 
pointX = flip Point 0
 
pointY = Point 0
 
pointEmpty = Point 0 0
 
type Circle = Circle x y z
 
instance Show Circle where
showf _ (Circle x y z) =
"Circle " ++ (show x) ++ " " ++ (show y) ++ " " ++ (show z)
 
instance Name Circle where
getField nm (Circle x y z)
| nm == "x" = x
| nm == "y" = y
| nm == "z" = z
| else = fail "Undefined name."
isField nm _ = nm == "x" or nm == "y" or nm == "z"
 
circleXZ = flip Circle 0
 
circleX x = Circle x 0 0
 
circleYZ = Circle 0
 
circleY y = Circle 0 y 0
 
circleZ = Circle 0 0
 
circleEmpty = Circle 0 0 0
 
circleX 1 2

Class Show is defined in prelude and is effectively an abstraction for all "printable" entities.

Normally, algebraic types are analyzed using pattern matching, however, it is possible to provide a support for an "accessor style" approach by providing an instance for class Name (which is also defined in prelude). With this instance it is possible to write code like so:

c = circleX 12
c.x //Evaluates to 12

[edit] Factor

QUALIFIED: io  ! there already is print in io
 
GENERIC: print ( shape -- )
 
TUPLE: point x y ;
C: <point> point  ! shorthand constructor definition
 
M: point print drop "Point" io:print ;
 
TUPLE: circle radius x y ;
C: <circle> circle
 
M: circle print drop "Circle" io:print ;

[edit] Forth

Works with: 4tH version 3.62.0

There are numerous, mutually incompatible object oriented frameworks for Forth. This one works with the FOOS preprocessor extension of 4tH. Variadic functions in Forth are usually implemented by passing the number of parameters. Since it is highly unlikely that objects are allocated that low in memory it works. Note that X, Y and Z are passed in reverse order, which is quite common for any Forth program.

include lib/memcell.4th
include 4pp/lib/foos.4pp
 
:: Point ( xn n a--)
class
field: x \ x coordinate
field: y \ y coordinate
method: print \ print routine
method: setx \ set x coordinate
method: sety \ set y coordinate
method: getx \ get x coordinate
method: gety \ get y coordinate
end-class {
\ bind the methods immediately
 :method { this -> x ! } ; defines setx
 :method { this -> y ! } ; defines sety
 :method { this -> x @ } ; defines getx
 :method { this -> y @ } ; defines gety
\ because we'll use them immediately
 :method { \ e.g. in this print routine
." Point(" this => getx 0 .r ." ," this => gety 0 .r ." )" cr
} ; defines print \ and this initialization
\ object or argument count
dup type@ this type@ = \ if it is an object, a point
if \ get the coordinates and set them
dup => getx this => setx
=> gety this => sety
else \ otherwise initialize it
0 dup this => setx this => sety
case \ and check the argument count
1 of this => setx endof \ one argument : x only
2 of this => setx \ two arguments: x and y
this => sety endof
endcase
then
 
private{ x y } \ make x and y private
}
;
 
:: Circle ( xn n a --)
over >r ( arg-count object-addr)
extends Point \ save the argument count!!
field: r \ radius
method: getr \ get radius
method: setr \ set radius
end-extends r> swap { \ retrieve count
\ bind the methods immediately
 :method { this -> r ! } ; defines setr
 :method { this -> r @ } ; defines getr
\ because we'll use them immediately
 :method { \ e.g. in this print routine
." Circle(" this => getx 0 .r ." ,"
this => gety 0 .r ." ,"
this => getr 0 .r ." )" cr
} ; defines print \ and this initialization
\ object or argument count
dup type@ this type@ = \ if it is an object, a circle
if \ get the coordinates and set them
dup => getx this => setx
dup => gety this => sety
=> getr this => setr
else \ otherwise initialize it
0 this => setr
case \ and check the argument count
3 of this => setr \ three arguments: x, y and r
this => sety \ note the rest is already set
this => setx endof \ by "Point" and r was left on
endcase \ the stack!
then
 
private{ r }
}
;
 
0 new Point Point1
Point1 => print
45 23 2 new Point Point2
Point2 => print
Point2 new Point Point3
Point3 => print
78 1 new Point Point4
Point4 => print
10 45 23 3 new Circle Circle1
Circle1 => print
Point2 new Circle Circle2
Circle2 => print
Circle1 new Circle Circle3
Circle3 => print

[edit] Fortran

Fortran provides OO features with the type mechanism. This example works with the Intel 11.1.069 compiler.

 
module geom
 
type point
real(8), private :: x = 0
real(8), private :: y = 0
contains
procedure, public :: get_x
procedure, public :: get_y
procedure, public :: set_x
procedure, public :: set_y
procedure, public :: print => print_point
end type point
 
type, extends(point) :: circle
real(8), private :: r = 0
contains
procedure, public :: get_r
procedure, public :: set_r
procedure, public :: print => print_circle
end type circle
 
contains
 
real(8) function get_x(this)
class(point), intent(in) :: this
get_x = this%x
end function get_x
 
real(8) function get_y(this)
class(point), intent(in) :: this
get_y = this%y
end function get_y
 
subroutine set_x(this, val)
class(point), intent(inout) :: this
real(8), intent(in) :: val
this%x = val
end subroutine set_x
 
subroutine set_y(this, val)
class(point), intent(inout) :: this
real(8), intent(in) :: val
this%y = val
end subroutine set_y
 
subroutine print_point(this)
class(point), intent(in) :: this
write(*,'(2(a,f0.4),a)') 'Point(',this%x,', ',this%y,')'
end subroutine print_point
 
real(8) function get_r(this)
class(circle), intent(in) :: this
get_r = this%r
end function get_r
 
subroutine set_r(this, val)
class(circle), intent(inout) :: this
real(8), intent(in) :: val
this%r = val
end subroutine set_r
 
subroutine print_circle(this)
class(circle), intent(in) :: this
write(*,'(3(a,f0.4),a)') 'Circle(',this%x,', ',this%y,'; ',this%r,')'
end subroutine print_circle
 
end module geom
 
program inh
use geom
 
type(point) :: p
type(circle) :: c
 
p = point(2.0d0, 3.0d0)
call p%print
 
c = circle(3.0d0, 4.0d0, 5.0d0)
call c%print
 
end program inh
 
 

[edit] F#

Polymorphism is achieved by defining an interface Printable which is implemented by Point and Circle. (In real code, you should override the ToString method which every class inherits from Object.)

Due to the use of optional parameters, we only need one constructor for every class. No accessors are necessary because we use public read-only properties. (Mutable properties are possible, too, but should be avoided in idiomatic code.)

type Printable =
abstract member Print : unit -> unit
 
type Point(?x, ?y) =
member t.x = defaultArg x 0.0
member t.y = defaultArg y 0.0
interface Printable with
member t.Print() = printfn "Point(x:%f, y:%f)" t.x t.y
 
type Circle(?center, ?radius) =
member t.center = defaultArg center (new Point())
member t.radius = defaultArg radius 1.0
interface Printable with
member t.Print() =
printfn "Circle(x:%f, y:%f, r:%f)" t.center.x t.center.y t.radius

[edit] Go

package main
 
import "fmt"
 
type point struct {
x, y float64
}
 
type circle struct {
x, y, r float64
}
 
type printer interface {
print()
}
 
func (p *point) print() {
fmt.Println(p.x, p.y)
}
 
func (c *circle) print() {
fmt.Println(c.x, c.y, c.r)
}
 
func main() {
var i printer // polymorphic variable
i = newPoint(3, 4) // assign one type
i.print() // call polymorphic function
i = newCircle(5, 12, 13) // assign different type to same variable
i.print() // same call accesses different method now.
}
 
// Above is a sort of polymorphism: both types implement the printer
// interface. The print function can be called through a variable
// of type printer, without knowing the underlying type.
 
// Below is other stuff the task asks for. Note that none of it is
// needed for cases as simple as this task, and it is not idomatic
// to write any of these functions in these simple cases.
 
// Accessors are not idiomatic in Go. Instead, simply access struct
// fields directly. To allow access from another package, you "export"
// the field by capitalizing the field name.
func (p *point) getX() float64 { return p.x }
func (p *point) getY() float64 { return p.y }
func (p *point) setX(v float64) { p.x = v }
func (p *point) setY(v float64) { p.y = v }
 
func (c *circle) getX() float64 { return c.x }
func (c *circle) getY() float64 { return c.y }
func (c *circle) getR() float64 { return c.r }
func (c *circle) setX(v float64) { c.x = v }
func (c *circle) setY(v float64) { c.y = v }
func (c *circle) setR(v float64) { c.r = v }
 
// Copy constructors, not idiomatic. Structs are assignable so
// you can simply declare and assign them as needed.
func (p *point) clone() *point { r := *p; return &r }
func (c *circle) clone() *circle { r := *c; return &r }
 
// Assignment methods, not idiomatic. Just use the assignment operator.
func (p *point) set(q *point) { *p = *q }
func (c *circle) set(d *circle) { *c = *d }
 
// Constructors are idiomatic only when construction involves something
// more than just assigning initial values. By default, structs
// are created as "zero values," that is, with all fields zero,
// empty, or nil. The struct literal synax allows for all fields to
// initialized, or for any subset of fields to be initialized by name.
// These feautures take the place of trivial default constructors.
// When additional initialization is needed, it is conventional to
// name a function New, New<Type>, or within a package, new<Type>
// as shown here.
func newPoint(x, y float64) *point {
return &point{x, y}
}
func newCircle(x, y, r float64) *circle {
return &circle{x, y, r}
}
 
// Destructors are never used in Go. Objects are garbage collected.

[edit] Groovy

@Canonical
@TupleConstructor(force = true)
@ToString(includeNames = true)
class Point {
Point(Point p) { x = p.x; y = p.y }
void print() { println toString() }
Number x
Number y
}
 
@Canonical
@TupleConstructor(force = true)
@ToString(includeNames = true, includeSuper = true)
class Circle extends Point {
Circle(Circle c) { super(c); r = c.r }
void print() { println toString() }
Number r
}

Test Code:

def p = new Point(x: 3, y: 4)
def c = new Circle(x: 4, y: 3, r: 5)
 
[(p): new Point(p), (c): new Circle(c)].each { v1, v2 ->
print "Verifying $v1 == "
v2.print()
assert v1 == v2
}

Output:

Verifying Point(x:3, y:4) == Point(x:3, y:4)
Verifying Circle(r:5, super:Point(x:4, y:3)) == Circle(r:5, super:Point(x:4, y:3))

[edit] Haskell

Polymorphism is achieved through the type class Show

data Point = Point Integer Integer
instance Show Point where
show (Point x y) = "Point at "++(show x)++","++(show y)
 
-- Constructor that sets y to 0
ponXAxis = flip Point 0
 
-- Constructor that sets x to 0
ponYAxis = Point 0
 
-- Constructor that sets x and y to 0
porigin = Point 0 0
 
data Circle = Circle Integer Integer Integer
instance Show Circle where
show (Circle x y r) = "Circle at "++(show x)++","++(show y)++" with radius "++(show r)
 
-- Constructor that sets y to 0
conXAxis = flip Circle 0
 
-- Constructor that sets x to 0
conYAxis = Circle 0
 
-- Constructor that sets x and y to 0
catOrigin = Circle 0 0
 
--Constructor that sets y and r to 0
c0OnXAxis = flip (flip Circle 0) 0
 
--Constructor that sets x and r to 0
c0OnYAxis = flip (Circle 0) 0

[edit] Icon and Unicon

This is Unicon specific, as Unicon has classes, but Icon does not.

There is no destructor, as Unicon manages object destruction itself. The copy constructor is emulated by a method. Notice the 'initially' clauses. These act like constructors, in that they accept input parameters during instance construction. These parameters are null if not used, and so the initial field values are set to 0 if the entered value is null (tested using the '/' symbol).

class Circle (x, y, r)
# make a new copy of this instance
method copy ()
return Circle (x, y, r)
end
 
# print a representation of this instance
method print ()
write ("Circle (" || x || ", " || y || ", " || r || ")")
end
 
# called during instance construction, to pass in field values
initially (x, y, r)
self.x := if /x then 0 else x # set to 0 if argument not present
self.y := if /y then 0 else y
self.r := if /r then 0 else r
 
end
 
class Point (x, y)
# make a new copy of this instance
method copy ()
return Point (x, y)
end
 
# print a representation of this instance
method print ()
write ("Point (" || x || ", " || y || ")")
end
 
# called during instance construction, to pass in field values
initially (x, y)
self.x := if /x then 0 else x # set to 0 if argument not present
self.y := if /y then 0 else y
 
end
 
procedure main ()
p1 := Point ()
p2 := Point (1)
p3 := Point (1,2)
p4 := p3.copy ()
 
write ("Points:")
p1.print ()
p2.print ()
p3.print ()
p4.print ()
# demonstrate field mutator/accessor
p3.x := 3
write ("p3 value of x is: " || p3.x)
 
c1 := Circle ()
c2 := Circle (1)
c3 := Circle (1,2)
c4 := Circle (1,2,3)
 
write ("Circles:")
c1.print ()
c2.print ()
c3.print ()
c4.print ()
end
 

[edit] Inform 7

Accessors are not needed since property values are public. Constructors and destructors are not needed since objects are statically allocated and initialized.

Space is a room.
 
A point is a kind of thing.
A point has a number called X position.
A point has a number called Y position.
 
A circle is a kind of point.
A circle has a number called radius.
 
To print (P - point): say "Point: [X position of P], [Y position of P]."
To print (C - circle): say "Circle: [X position of C], [Y position of C] radius [radius of C]."
 
The origin is a point with X position 0 and Y position 0.
The circle of power is a circle with X position 100, Y position 25, radius 7.
 
When play begins:
print the origin;
print the circle of power;
end the story.

[edit] J

coclass 'Point'
create=: monad define
'X Y'=:2{.y
)
getX=: monad def 'X'
getY=: monad def 'Y'
setX=: monad def 'X=:y'
setY=: monad def 'Y=:y'
print=: monad define
smoutput 'Point ',":X,Y
)
destroy=: codestroy
coclass 'Circle'
coinsert 'Point'
create=: monad define
'X Y R'=: 3{.y
)
getR=: monad def 'R'
setR=: monad def 'R=:y'
print=: monad define
smoutput 'Circle ',":X,Y,R
)

[edit] Java

class Point {
protected int x, y;
public Point() { this(0); }
public Point(int x0) { this(x0, 0); }
public Point(int x0, int y0) { x = x0; y = y0; }
public Point(Point p) { this(p.x, p.y); }
public int getX() { return x; }
public int getY() { return y; }
public int setX(int x0) { x = x0; }
public int setY(int y0) { y = y0; }
public void print() { System.out.println("Point"); }
}
 
public class Circle extends Point {
private int r;
public Circle(Point p) { this(p, 0); }
public Circle(Point p, int r0) { super(p); r = r0; }
public Circle() { this(0); }
public Circle(int x0) { this(x0, 0); }
public Circle(int x0, int y0) { this(x0, y0, 0); }
public Circle(int x0, int y0, int r0) { super(x0, y0); r = r0; }
public Circle(Circle c) { this(c.x, c.y, c.r); }
public int getR() { return r; }
public int setR(int r0) { r = r0; }
public void print() { System.out.println("Circle"); }
 
public static void main(String args[]) {
Point p = new Point();
Point c = new Circle();
p.print();
c.print();
}
}

[edit] JavaScript

/* create new Point in one of these ways:
* var p = new Point(x,y);
* var p = new Point(a_point);
* default value for x,y is 0
*/

function Point() {
var arg1 = arguments[0];
var arg2 = arguments[1];
 
if (arg1 instanceof Point) {
this.x = arg1.x;
this.y = arg1.y;
}
else {
this.x = arg1 == null ? 0 : arg1;
this.y = arg2 == null ? 0 : arg1;
}
 
this.set_x = function(_x) {this.x = _x;}
this.set_y = function(_y) {this.y = _y;}
}
 
Point.prototype.print = function() {
var out = "Point(" + this.x + "," + this.y + ")";
print(out);
}
 
/* create new Circle in one of these ways:
* var c = new Circle(x,y,r);
* var c = new Circle(a_circle);
* var c = new Circle(a_point,r);
* default value for x,y,r is 0
*/

function Circle() {
var arg1 = arguments[0];
var arg2 = arguments[1];
var arg3 = arguments[2];
 
if (arg1 instanceof Circle) {
this.x = arg1.x;
this.y = arg1.y;
this.r = arg1.r;
}
else if (arg1 instanceof Point) {
this.x = arg1.x;
this.y = arg1.y;
this.r = arg2 == null ? 0 : arg2;
}
else {
this.x = arg1 == null ? 0 : arg1;
this.y = arg2 == null ? 0 : arg2;
this.r = arg3 == null ? 0 : arg3;
}
 
this.set_x = function(_x) {this.x = _x;}
this.set_y = function(_y) {this.y = _y;}
this.set_r = function(_r) {this.r = _r;}
}
 
Circle.prototype.print = function() {
var out = "Circle(" + this.x + "," + this.y + "," + this.r + ")";
print(out);
}

[edit] Julia

There is no obvious inheritance hierarchy here to get polymorphism. Julia has multiple dispatch, so the appropriate implementation of the print function will be called at runtime depending on the type of the arguments provided. The import of Base.print is done to allow the print function to dispatch on some new types you define.

It would not be idiomatic to define setters and getters for a type like this in Julia. One would just access the fields directly. There is no need to explicitly define a constructor since that is automatically provided. You only roll your own if you need more elaborate initialization or you need to set default values.

 
 
import Base.print
 
type Point
x::Float64
y::Float64
end
 
print(p::Point) = println("Point($(p.x), $(p.y))")
 
x(p::Point) = p.x
y(p::Point) = p.y
 
setx(p::Point, x) = (p.x = x)
sety(p::Point, y) = (p.y = y)
 
type Circle
x::Float64
y::Float64
r::Float64
end
 
x(c::Circle) = c.x
y(c::Circle) = c.y
r(c::Circle) = c.r
 
setx(c::Circle, x) = (c.x = x)
sety(c::Circle, y) = (c.y = y)
setr(c::Circle, r) = (c.r = r)
 
print(c::Circle) = println("Circle($(c.x), $(c.y), $(c.r))")
 

[edit] Lua

Lua does not have a standard definition of objects or classes, so a basic and typical protoctype-based OOP model will be used. In Lua all objects are tables, and through the use of metatables, polymorphism can be achieved in many ways, this is only one of them.

-- Point
local Point = {x = 0, y = 0}
 
function Point:new(o)
o = o or {}
setmetatable(o, self)
self.__index = self
return o
end
 
function Point:print()
print("Point(" .. self.x .. ", " .. self.y .. ")")
end
 
function Point:copy()
return Point:new{x = self.x, y = self.y}
end
 
-- Circle
local Circle = Point:new()
Circle.r = 0
 
function Circle:print()
print("Circle(" .. self.x .. ", " .. self.y .. ", " .. self.r .. ")")
end
 
function Circle:copy()
return Circle:new{x = self.x, y = self.y, r = self.r}
end

[edit] NetRexx

Note: Based on default values in method prototypes, NetRexx will automatically generate intermediate constructors and methods, thus ensuring that none are omitted.

/* NetRexx */
 
options replace format comments java crossref savelog symbols binary
 
-- -----------------------------------------------------------------------------
class RCPolymorphism public final
 
method main(args = String[]) public constant
 
parry = [Point -
Point() -
, Point(1.0) -
, Point(1.0, 2.0) -
, Point(Point(0.3, 0.2)) -
, Circle() -
, Circle(2.0, 2.0) -
, Circle(5.0, 6.0, 7.0) -
, Circle(Point(8.0, 9.0)) -
, Circle(Point(8.0, 9.0), 4.0) -
, Circle(Circle(1.5, 1.4, 1.3)) -
]
 
loop pp = 0 to parry.length - 1
parry[pp].print
end pp
 
return
 
-- -----------------------------------------------------------------------------
class RCPolymorphism.Point public binary
 
properties private
x = double
y = double
className = Point.class.getSimpleName
 
method Point(x_ = double 0.0, y_ = double 0.0)
setX(x_)
setY(y_)
return
 
method Point(p = Point)
this(p.getX, p.getY)
return
 
method display public returns String
hx = '@'Rexx(Integer.toHexString(hashCode())).right(8, 0)
str = Rexx(className).left(10)':'hx': (x,y) = (' || -
Rexx(getX()).format(null, 3)',' -
Rexx(getY()).format(null, 3)')'
return str
 
method getX public returns double
return x
 
method getY public returns double
return y
 
method setX(x_ = double 0.0) inheritable
x = x_
return
 
method setY(y_ = double 0.0) inheritable
y = y_
return
 
method print inheritable
say display
return
 
-- -----------------------------------------------------------------------------
class RCPolymorphism.Circle public extends RCPolymorphism.Point binary
 
properties private
r = double
className = Circle.class.getSimpleName
 
method Circle(x_ = double 0.0, y_ = double 0.0, r_ = double 0.0)
super(x_, y_)
setR(r_)
return
 
method Circle(p_ = RCPolymorphism.Point, r_ = double 0.0)
this(p_.getX, p_.getY, r_)
return
 
method Circle(c_ = Circle)
this(c_.getX, c_.getY, c_.getR)
return
 
method getR public returns double
return r
 
method setR(r_ = double 0.0) inheritable
r = r_
return
 
method display public returns String
hx = '@'Rexx(Integer.toHexString(hashCode())).right(8, 0)
str = Rexx(className).left(10)':'hx': (x,y,r) = (' || -
Rexx(getX()).format(null, 3)',' -
Rexx(getY()).format(null, 3)',' -
Rexx(getR()).format(null, 3)')'
return str
 
Output
Point     :@0eb42cbf: (x,y) = (0.000, 0.000)
Point     :@17dfafd1: (x,y) = (1.000, 0.000)
Point     :@3343c8b3: (x,y) = (1.000, 2.000)
Point     :@272d7a10: (x,y) = (0.300, 0.200)
Circle    :@1aa8c488: (x,y,r) = (0.000, 0.000, 0.000)
Circle    :@3dfeca64: (x,y,r) = (2.000, 2.000, 0.000)
Circle    :@22998b08: (x,y,r) = (5.000, 6.000, 7.000)
Circle    :@0e76cbf7: (x,y,r) = (8.000, 9.000, 0.000)
Circle    :@1948cc8c: (x,y,r) = (8.000, 9.000, 4.000)
Circle    :@7a6d084b: (x,y,r) = (1.500, 1.400, 1.300)

[edit] Nimrod

Similar to the Python solution:

type
Point = object
x, y: float
 
Circle = object
center: Point
radius: float
 
# Constructors
proc createPoint(x, y = 0.0): Point =
result.x = x
result.y = y
 
proc createCircle(x, y = 0.0, radius = 1.0): Circle =
result.center.x = x
result.center.y = y
result.radius = radius
 
var p1 = createPoint()
echo "p1: ", p1 # We use the default $ operator for printing
var p2 = createPoint(3, 4.2)
var p3 = createPoint(x = 2)
var p4 = createPoint(y = 2.5)
 
p2 = p4
p3 = createPoint()
 
var c1 = createCircle()
echo "c1: ", c1
var c2 = createCircle(2, 0.5, 4.2)
var c3 = createCircle(x = 2.1, y = 2)
var c4 = createCircle(radius = 10)
 
c1.center.x = 12
c1.radius = 5.2

Output:

p1: (x: 0.0, y: 0.0)
c1: (center: (x: 0.0, y: 0.0), radius: 1.0)

[edit] Objeck

 
bundle Default {
class Point {
@x : Int;
@y : Int;
 
New() {
@x := 0;
@y := 0;
}
 
New(x : Int, y : Int) {
@x := x;
@y := y;
}
 
New(p : Point) {
@x := p->GetX();
@y := p->GetY();
}
 
method : public : GetX() ~ Int {
return @x;
}
 
method : public : GetY() ~ Int {
return @y;
}
 
method : public : SetX(x : Int) ~ Nil {
@x := x;
}
 
method : public : SetY(y : Int) ~ Nil {
@y := y;
}
 
method : public : Print() ~ Nil {
"Point"->PrintLine();
}
}
 
 
class Circle from Point {
@r : Int;
 
New() {
Parent();
@r := 0;
}
 
New(p : Point) {
Parent(p);
@r := 0;
}
 
New(c : Circle) {
Parent(c->GetX(), c->GetY());
@r := c->GetR();
}
 
method : public : GetR() ~ Int {
return @r;
}
 
method : public : SetR(r : Int) ~ Nil {
@r := r;
}
 
method : public : Print() ~ Nil {
"Circle"->PrintLine();
}
}
 
class Poly {
function : Main(args : String[]) ~ Nil {
p := Point->New();
c := Circle->New();
p->Print();
c->Print();
}
}
}
 

[edit] Objective-C

#import <Foundation/Foundation.h>
 
@interface RCPoint : NSObject {
int x, y;
}
-(instancetype)initWithX:(int)x0;
-(instancetype)initWithX:(int)x0 andY:(int)y0;
-(instancetype)initWithPoint:(RCPoint *)p;
@property (nonatomic) int x;
@property (nonatomic) int y;
@end
 
@implementation RCPoint
@synthesize x, y;
-(instancetype)initWithX:(int)x0 { return [self initWithX:x0 andY:0]; }
-(instancetype)initWithX:(int)x0 andY:(int)y0 {
if ((self = [super init])) {
x = x0;
y = y0;
}
return self;
}
-(instancetype)initWithPoint:(RCPoint *)p { return [self initWithX:p.x andY:p.y]; }
-(NSString *)description { return [NSString stringWithFormat:@"<RCPoint %p x: %d y: %d>", self, x, y]; }
@end
 
@interface RCCircle : RCPoint {
int r;
}
-(instancetype)initWithCenter:(RCPoint *)p andRadius:(int)r0;
-(instancetype)initWithX:(int)x0 andY:(int)y0 andRadius:(int)r0;
-(instancetype)initWithCircle:(RCCircle *)c;
@property (nonatomic) int r;
@end
 
@implementation RCCircle
@synthesize r;
-(instancetype)initWithCenter:(RCPoint *)p andRadius:(int)r0 {
if ((self = [super initWithPoint:p])) {
r = r0;
}
return self;
}
-(instancetype)initWithX:(int)x0 andY:(int)y0 andRadius:(int)r0 {
if ((self = [super initWithX:x0 andY:y0])) {
r = r0;
}
return self;
}
-(instancetype)initWithCircle:(RCCircle *)c { return [self initWithX:c.x andY:c.y andRadius:c.r]; }
-(NSString *)description { return [NSString stringWithFormat:@"<RCCircle %p x: %d y: %d r: %d>", self, x, y, r]; }
@end
 
int main(int argc, const char *argv[]) {
@autoreleasepool {
 
NSLog(@"%@", [[RCPoint alloc] init]);
NSLog(@"%@", [[RCPoint alloc] initWithX:3]);
NSLog(@"%@", [[RCPoint alloc] initWithX:3 andY:4]);
NSLog(@"%@", [[RCCircle alloc] init]);
NSLog(@"%@", [[RCCircle alloc] initWithX:3]);
NSLog(@"%@", [[RCCircle alloc] initWithX:3 andY:4]);
NSLog(@"%@", [[RCCircle alloc] initWithX:3 andY:4 andRadius:7]);
RCPoint *p = [[RCPoint alloc] initWithX:1 andY:2];
NSLog(@"%@", [[RCCircle alloc] initWithPoint:p]);
NSLog(@"%@", [[RCCircle alloc] initWithCenter:p andRadius:7]);
NSLog(@"%d", p.x); // 1
p.x = 8;
NSLog(@"%d", p.x); // 8
 
}
return 0;
}

[edit] OCaml

class point ?(x=0.0) ?(y=0.0) () = (* extra () used to erase the optional parameters *)
object (self)
val mutable x = x
val mutable y = y
 
method x = x
method y = y
method set_x x' = x <- x'
method set_y y' = y <- y'
method print = Printf.sprintf "Point (%f, %f)" x y
method copy = {< >}
end
 
class circle ?(r=1.0) ?(x=0.0) ?(y=0.0) () =
object (self)
inherit point ~x:x ~y:y ()
val mutable r = r
 
method r = r
method set_r r' = r <- r'
method print = Printf.sprintf "Circle (%f, %f, %f)" r x y
end
 
let print x = print_endline x#print
 
let () =
let p = new point () in
let c = new circle () in
print c;
print p;
c#set_x 10.0;
print c;
print (new point ~y:2.1 ())

[edit] ooRexx

ooRexx supports traditional class-based polymorphism. The polymorphic methods can be part of the main class sequence or brought in using mixins for multiple inheritance situations. Here is a simple example using point and circle classes in a hierarchy.

 
p = .point~new(3,2)
c = .circle~new(,2,6)
 
p~print
c~print
 
::class point
::method init
expose x y
use strict arg x = 0, y = 0 -- defaults to 0 for any non-specified coordinates
 
::attribute x
::attribute y
 
::method print
expose x y
say "A point at location ("||x","y")"
 
::class circle subclass point
::method init
expose radius
use strict arg x = 0, y = 0, radius = 0
self~init:super(x, y) -- call superclass constructor
 
::attribute radius
 
::method print
expose radius
say "A circle of radius" radius "centered at location ("||self~x","self~y")"
 
 

Output:

A point at location (3,2)
A circle of radius 6 centered at location (0,2) 


Method binding in ooRexx is late and dynamic. In many situations, polymorphism can be achieved merely by providing an expected method. It is not necessary for an object to be of a particular class hierarchy. In the example below, both point and circle implement a print method, but there is no class relationship between these classes other than what they inherit from the object class.

 
p = .point~new(3,2)
c = .circle~new(,2,6)
 
p~print
c~print
 
::class point
::method init
expose x y
use strict arg x = 0, y = 0 -- defaults to 0 for any non-specified coordinates
 
::attribute x
::attribute y
 
::method print
expose x y
say "A point at location ("||x","y")"
 
::class circle
::method init
expose x y radius
use strict arg x = 0, y = 0, radius = 0
 
::attribute radius
::attribute x
::attribute y
 
::method print
expose radius x y
say "A circle of radius" radius "centered at location ("||x","y")"
 
 

Output:

A point at location (3,2)
A circle of radius 6 centered at location (0,2) 


[edit] OxygenBasic

Also uses method overloading, named parameters in the constructors, inheritance with method overrides.

Other primitives convert to floats automatically

A compact format for the methods is used to improve layout.

 
type tpoint float xx,yy
type tcircle float xx,yy,rr
 
'==========
class point
'==========
'
has tpoint
'
method constructor (float x=0,y=0){this<=x,y}
method destructor {}
method V() as point {return @this}
method V(tpoint*a) {this<=a.xx,a.yy}
method V(point *a) {this<=a.xx,a.yy}
method X() as float {return xx}
method Y() as float {return yy}
method X(float a) {xx=a}
method Y(float a) {yy=a}
method clear() {this<=.0,.0}
method show() as string {return "x=" xx ", y=" yy }
'
end class
 
 
'===========
class circle
'===========
'
has point
float rr
'
method constructor (float x=.0,y=.0,r=1.0){this<=x,y,r}
method V(tcircle*a) {this<=a.xx,a.yy,a.rr}
method V(circle *a) {this<=a.xx,a.yy,a.rr}
method R() as float {return rr}
method R(float a) {rr=a}
method clear() {this<=.0,.0,.0}
method show() as string {return "x=" xx ", y=" yy ", r=" rr }
'
end class
 
'=====
'TESTS
'=====
 
new circle ca (r=.5)
new circle cb (x=10,y=10)
new circle cc (10,10,0.5)
 
cb.r="7.5" 'will convert a string value
 
cb.y=20
 
print cb.show 'result x=10, y=20 ,r=7.5
 
del ca : del cb : del cc
 

[edit] Oz

No inheritance necessary for polymorphism, so we don't use it here (a circle is certainly not a point). Default constructors are implemented by named default arguments. No accessors because we use immutable public attributes ("features").

class Point
feat
x
y
 
meth init(x:X<=0.0 y:Y<=0.0)
self.x = X
self.y = Y
end
 
meth print
{System.showInfo
"Point("#
"x:"#self.x#
", y:"#self.y#
")"}
end
end
 
class Circle
feat
center
r
 
meth init(center:C<={New Point init} r:R<=1.0)
self.center = C
self.r = R
end
 
meth print
{System.showInfo
"Circle("#
"x:"#self.center.x#
", y:"#self.center.y#
", r:"#self.r#
")"}
end
end

[edit] Pascal

See Delphi

[edit] Perl

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.

{
package Point;
use Class::Spiffy -base;
use Clone qw(clone);
 
sub _print {
my %self = %{shift()};
while (my ($k,$v) = each %self) {
print "$k: $v\n";
}
}
 
sub members {
no strict;
grep {
1 == length and defined *$_{CODE}
} keys %{*{__PACKAGE__."\::"}};
}
 
sub new {
my $class = shift;
my %param = @_;
$param{$_} = 0 for grep {!defined $param{$_}} members;
bless \%param, $class;
}
 
sub copy_constructor {
clone shift;
}
 
sub copy_assignment {
my $self = shift;
my $from = shift;
$self->$_($from->$_) for $from->members;
}
 
field 'x';
field 'y';
}
 
{
package Circle;
use base qw(Point);
field 'r';
}
 
{
package main;
$_->_print, print "\n" for (
Point->new,
Point->new(x => 2),
Point->new(y => 3),
Point->new(x => 8, y => -5),
);
my $p1 = Point->new(x => 8, y => -5);
 
my $p2 = $p1->copy_constructor;
print "we are really different objects, not just references ".
"to the same instance\n" unless \$p1 eq \$p2;
 
# accessors autogenerated
$p1->x(1);
$p1->y(2);
print $p1->x, "\n";
print $p1->y, "\n";
 
$p2->copy_assignment($p1);
print $p2->x, "\n";
print $p2->y, "\n";
print "we now have the same values, but we are still ".
"different objects\n" unless \$p1 eq \$p2;
 
$_->_print, print "\n" for (
Circle->new,
Circle->new(x => 1),
Circle->new(y => 2),
Circle->new(r => 3),
Circle->new(x => 4, y => 5),
Circle->new(x => 6, r => 7),
Circle->new(y => 8, r => 9),
Circle->new(x => 1, y => 2, r => 3),
);
 
my $c = Circle->new(r => 4);
print $c->r, "\n"; # accessor autogenerated
}

[edit] Perl 6

All appropriate constructors, initializers, accessors, and destructors are provided by default, but may be explicitly declared for flexibility. To create only readonly accessors for better encapsulation, leave out all the "is rw" traits. Here we demonstrate that accessors can behave like variables and may be assigned.

class Point {
has Num $.x is rw = 0;
has Num $.y is rw = 0;
method Str { $.perl }
}
 
class Circle {
has Point $.p is rw = Point.new;
has Num $.r is rw = 0;
method Str { $.perl }
}
 
my $c = Circle.new(Point.new(x => 1, y => 2), r => 3);
say $c;
$c.p.x = (-10..10).pick;
$c.p.y = (-10..10).pick;
$c.r = (0..10).pick;
say $c;

In this case we define the Str coercion method polymorphically, which is used by say or print to format the contents of the object. We could also have defined print methods directly. We could have factored this method out to a common role and composed it into each class. We could also have defined multi subs outside of the class, like this:

multi print (Point $p) { $p.perl.print }
multi print (Circle $c) { $c.perl.print }

[edit] PHP

'print' is a reserved keyword in PHP so the method to print is called 'output'. Alternatively the Point and Circle objects can be converted to a string representation by simply printing / echo'ing the object because the objects implement the magic '__toString' method.


Point class definition.

 
class Point
{
protected $_x;
 
protected $_y;
 
public function __construct()
{
switch( func_num_args() )
{
case 1:
$point = func_get_arg( 0 );
$this->setFromPoint( $point );
break;
case 2:
$x = func_get_arg( 0 );
$y = func_get_arg( 1 );
$this->setX( $x );
$this->setY( $y );
break;
default:
throw new InvalidArgumentException( 'expecting one (Point) argument or two (numeric x and y) arguments' );
}
}
 
public function setFromPoint( Point $point )
{
$this->setX( $point->getX() );
$this->setY( $point->getY() );
}
 
public function getX()
{
return $this->_x;
}
 
public function setX( $x )
{
if( !is_numeric( $x ) )
{
throw new InvalidArgumentException( 'expecting numeric value' );
}
 
$this->_x = (float) $x;
}
 
public function getY()
{
return $this->_y;
}
 
public function setY( $y )
{
if( !is_numeric( $y ) )
{
throw new InvalidArgumentException( 'expecting numeric value' );
}
 
$this->_y = (float) $y;
}
 
public function output()
{
echo $this->__toString();
}
 
public function __toString()
{
return 'Point [x:' . $this->_x . ',y:' . $this->_y . ']';
}
}
 

Circle class definition.

 
class Circle extends Point
{
private $_radius;
 
public function __construct()
{
switch( func_num_args() )
{
case 1:
$circle = func_get_arg( 0 );
$this->setFromCircle( $circle );
break;
case 2:
$point = func_get_arg( 0 );
$radius = func_get_arg( 1 );
$this->setFromPoint( $point );
$this->setRadius( $radius );
break;
case 3:
$x = func_get_arg( 0 );
$y = func_get_arg( 1 );
$radius = func_get_arg( 2 );
$this->setX( $x );
$this->setY( $y );
$this->setRadius( $radius );
break;
default:
throw new InvalidArgumentException( 'expecting one (Circle) argument or two (Point and numeric radius) or three (numeric x, y and radius) arguments' );
}
}
 
public function setFromCircle( Circle $circle )
{
$this->setX( $circle->getX() );
$this->setY( $circle->getY() );
$this->setRadius( $circle->getRadius() );
}
 
public function getPoint()
{
return new Point( $this->getX(), $this->getY() );
}
 
public function getRadius()
{
return $this->_radius;
}
 
public function setRadius( $radius )
{
if( !is_numeric( $radius ) )
{
throw new InvalidArgumentException( 'expecting numeric value' );
}
 
$this->_radius = (float) $radius;
}
 
public function __toString()
{
return 'Circle [' . $this->getPoint() . ',radius:' . $this->_radius . ']';
}
}
 

Usage:

 
$point = new Point( 1, 5 );
$circle = new Circle( 1, 5, 6 );
 
$point->output();
// or
echo $point;
 
echo "\n";
 
$circle->output();
// or
echo $circle;
 

Will result in:

Point [x:1,y:5]
Circle [Point [x:1,y:5],radius:6]

[edit] PicoLisp

(class +Point)
# x y
 
(dm T (X Y)
(=: x (or X 0))
(=: y (or Y 0)) )
 
(dm print> ()
(prinl "Point " (: x) "," (: y)) )
 
(class +Circle +Point)
# r
 
(dm T (X Y R)
(super X Y)
(=: r (or R 0)) )
 
(dm print> ()
(prinl "Circle " (: x) "," (: y) "," (: r)) )
(setq
P (new '(+Point) 3 4)
C (new '(+Circle) 10 10 5) )
 
(print> P)
(print> C)

Output:

Point 3,4
Circle 10,10,5

[edit] Pop11

When class is defined in Pop11 it automatically defines default constructors, slot accessors and copy operations. So it is enough to define classes and the print method.

uses objectclass;
define :class Point;
slot x = 0;
slot y = 0;
enddefine;
 
define :class Circle;
slot x = 0;
slot y = 0;
slot r = 1;
enddefine;
 
define :method print(p : Point);
printf('Point(' >< x(p) >< ', ' >< y(p) >< ')\n');
enddefine;
 
define :method print(p : Circle);
printf('Circle(' >< x(p) >< ', ' >< y(p) >< ', ' >< r(p) >< ')\n');
enddefine;

To test we can use the following code:

;;; Initialize variables using default constructors
lvars instance1 = newPoint();
lvars instance2 = newCircle();
;;; Use print method
print(instance1);
print(instance2);

[edit] PureBasic

Using the open-source precompiler SimlpeOOP.

Class MyPoint
 
BeginProtect
x.i
y.i
EndProtect
 
Public Method GetX()
MethodReturn This\X
EndMethod
 
Public Method GetY()
MethodReturn This\Y
EndMethod
 
Public Method SetX(n)
This\X=n
EndMethod
 
Public Method SetY(n)
This\Y=n
EndMethod
 
Public Method Print()
PrintN("Point")
EndMethod
 
Public Method Init(x=0,y=0)
This\x=x
This\y=y
EndMethod
EndClass
 
Class Circle Extends MyPoint
 
Protect Radie.i
 
Public Method Circel(x=0, y=0, r=0)
This\X = x
This\y = y
This\Radie=r
EndMethod
 
Public Method GetRadie()
MethodReturn This\Radie
EndMethod
 
Public Method SetRadie(n)
This\Radie = n
EndMethod
 
Public Method Print()
PrintN("Circle: "+ _
" X= "+Str(This\X)+ _
" Y= "+Str(This\Y)+ _
" R= "+Str(This\Radie))
EndMethod
 
EndClass

Testcode

*point.MyPoint = NewObject.MyPoint
*circle.Circle = NewObject.Circle
 
If OpenConsole()
*point\Print()
*circle\SetX(3)
*circle\Print()
CloseConsole()
EndIf

[edit] Python

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.

class Point(object):
def __init__(self, x=0.0, y=0.0):
self.x = x
self.y = y
def __repr__(self):
return '<Point 0x%x x: %f y: %f>' % (id(self), self.x, self.y)
 
class Circle(object):
def __init__(self, center=None, radius=1.0):
self.center = center or Point()
self.radius = radius
def __repr__(self):
return '<Circle 0x%x x: %f y: %f radius: %f>' % (
id(self), self.center.x, self.center.y, self.radius)

Usage example:

>>> from polymorphism import Point, Circle
>>> p1 = Point()
>>> Point()
<Point 0x5b1b0 x: 0.000000 y: 0.000000>
>>> Point(3, 4)
<Point 0x5b0f0 x: 3.000000 y: 4.000000>
>>> Point(y=4)
<Point 0x5b0b0 x: 0.000000 y: 4.000000>
>>> Point(x=3)
<Point 0x5b1b0 x: 3.000000 y: 0.000000>
>>> Circle()
<Circle 0x5b330 x: 0.000000 y: 0.000000 radius: 1.000000>
>>> Circle(Point(3,4))
<Circle 0x5b3b0 x: 3.000000 y: 4.000000 radius: 1.000000>
>>> Circle(Point(3,4), 7)
<Circle 0x5b3d0 x: 3.000000 y: 4.000000 radius: 7.000000>
>>> Circle(radius=10)
<Circle 0x5b0f0 x: 0.000000 y: 0.000000 radius: 10.000000>
>>> Circle(center=Point(127,0))
<Circle 0x5b0b0 x: 127.000000 y: 0.000000 radius: 1.000000>
>>> p = Point(1.25, 3.87)
>>> p
<Point 0x5b3d0 x: 1.250000 y: 3.870000>
>>> p.x = 10.81
>>> p
<Point 0x5b3d0 x: 10.810000 y: 3.870000>
>>> c = Circle(p, 21.4)
>>> c
<Circle 0x5b0b0 x: 10.810000 y: 3.870000 radius: 21.400000>
>>> c.center.x = 1.0
>>> c
<Circle 0x5b0b0 x: 1.000000 y: 3.870000 radius: 21.400000>

Or, using inheritance like some of the other solutions:

class Point(object):
def __init__(self, x=0.0, y=0.0):
self.x = x
self.y = y
def __repr__(self):
return '<Point 0x%x x: %f y: %f>' % (id(self), self.x, self.y)
 
class Circle(Point):
def __init__(self, x=0.0, y=0.0, radius=1.0):
Point.__init__(self, x, y)
self.radius = radius
def __repr__(self):
return '<Circle 0x%x x: %f y: %f radius: %f>' % (
id(self), self.x, self.y, self.radius)

Usage example:

>>> from polymorphism import Point, Circle
>>> p1 = Point()
>>> Point()
<Point 0x5b1b0 x: 0.000000 y: 0.000000>
>>> Point(3, 4)
<Point 0x5b0f0 x: 3.000000 y: 4.000000>
>>> Point(y=4)
<Point 0x5b0b0 x: 0.000000 y: 4.000000>
>>> Point(x=3)
<Point 0x5b1b0 x: 3.000000 y: 0.000000>
>>> Circle()
<Circle 0x5b330 x: 0.000000 y: 0.000000 radius: 1.000000>
>>> Circle(3, 4)
<Circle 0x5b3b0 x: 3.000000 y: 4.000000 radius: 1.000000>
>>> Circle(3, 4, 7)
<Circle 0x5b3d0 x: 3.000000 y: 4.000000 radius: 7.000000>
>>> Circle(radius=10)
<Circle 0x5b0f0 x: 0.000000 y: 0.000000 radius: 10.000000>
>>> Circle(x=127)
<Circle 0x5b0b0 x: 127.000000 y: 0.000000 radius: 1.000000>
>>> p = Point(1.25, 3.87)
>>> p
<Point 0x5b3d0 x: 1.250000 y: 3.870000>
>>> p.x = 10.81
>>> p
<Point 0x5b3d0 x: 10.810000 y: 3.870000>
>>> c = Circle(p.x, p.y, 21.4)
>>> c
<Circle 0x5b0b0 x: 10.810000 y: 3.870000 radius: 21.400000>
>>> c.x = 1.0
>>> c
<Circle 0x5b0b0 x: 1.000000 y: 3.870000 radius: 21.400000>

[edit] Mutability

The task calls for the creation of mutable types i.e that you are allowed to change the values of x, y, or r of a Point or Circle after they have been created. If this is not needed, then the Python namedtuple is a good way to create immutable classes with named fields such as these.

>>> from collections import namedtuple
>>> class Point(namedtuple('Point', 'x y')):
def __new__( _cls, x=0, y=0 ):
return super().__new__(_cls, x, y)
 
 
>>> class Circle(namedtuple('Circle', 'x y r')):
def __new__( _cls, x=0, y=0, r=0 ):
return super().__new__(_cls, x, y, r)
 
 
>>> Point(), Point(x=1), Point(y=2), Point(3, 4)
(Point(x=0, y=0), Point(x=1, y=0), Point(x=0, y=2), Point(x=3, y=4))
>>> Circle(), Circle(r=2), Circle(1, 2, 3)
(Circle(x=0, y=0, r=0), Circle(x=0, y=0, r=2), Circle(x=1, y=2, r=3))
>>> p = Point(1.25, 3.87)
>>> p
Point(x=1.25, y=3.87)
>>> p.x = 10.81
Traceback (most recent call last):
File "<pyshell#27>", line 1, in <module>
p.x = 10.81
AttributeError: can't set attribute
>>>

And if you don't need default arguments, this becomes:

>>> Point = namedtuple('Point', 'x y')
>>> Circle = namedtuple('Circle', 'x y r')
>>> Point(3, 4)
Point(x=3, y=4)
>>> Circle(x=1, y=2, r=3)
Circle(x=1, y=2, r=3)
>>>

[edit] R

Only the S4 class system is considered here. Copy constructors are not needed, since objects are copied by value. Neither are destructors needed (just use the rm function).

setClass("point",
representation(
x="numeric",
y="numeric"),
prototype(
x=0,
y=0))
 
# Instantiate class with some arguments
p1 <- new("point", x=3)
# Access some values
p1@x # 3
# Define a print method
setMethod("print", signature("point"),
function(x, ...)
{
cat("This is a point, with location, (", x@x, ",", x@y, ").\n")
})
print(p1)
 
# Define a circle class
setClass("circle",
representation(
centre="point",
r="numeric"),
prototype(
centre=new("point"),
r=1))
circS4 <- new("circle", r=5.5)
# Access some values
circS4@r # 5.5
circS4@centre@x # 0
# Define a print method
setMethod("print", signature("circle"),
function(x, ...)
{
cat("This is a circle, with radius", x@r, "and centre (", x@centre@x, ",", x@centre@y, ").\n")
})
print(circS4)

[edit] Racket

All arguments have default values provided, so every possible constructor is implicitly defined. "Fields" come with accessors and mutators for free.

 
#lang racket
(define point%
(class* object% (writable<%>) (super-new) (init-field [x 0] [y 0])
(define/public (copy) (new point% [x x] [y y]))
(define/public (show) (format "<point% ~a ~a>" x y))
(define/public (custom-write out) (write (show) out))
(define/public (custom-display out) (display (show) out))))
 
(define circle%
(class point% (super-new) (inherit-field x y) (init-field [r 0])
(define/override (copy) (new circle% [x x] [y y] [r r]))
(define/override (show) (format "<circle% ~a ~a>" (super show) r))
(define/override (custom-write out) (write (show) out))
(define/override (custom-display out) (display (show) out))))
 
Output:
> (define c (new circle% [x 3] [r 5]))
> (define dup (send c copy))
> c
"<circle% <point% 3 0> 5>"
> dup
"<circle% <point% 3 0> 5>"
> (set-field! r c 10)
> c
"<circle% <point% 3 0> 10>"
> (set-field! x c -2)
> c
"<circle% <point% -2 0> 10>"
> dup
"<circle% <point% 3 0> 5>"

[edit] Ruby

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. Due to duck typing, the two classes do not need to inherit from each other. The Kernel#dup method can be used as a copy constructor.

class Point
attr_accessor :x,:y
def initialize(x=0,y=0)
self.x=x
self.y=y
end
def to_s
"Point at #{x},#{y}"
end
end
 
class Circle
attr_accessor :x,:y,:r
def initialize(x=0,y=0,r=0)
self.x=x
self.y=y
self.r=r
end
def to_s
"Circle at #{x},#{y} with radius #{r}"
end
end

Example:

# create a point
p = Point.new(1, 2)
puts p  # => Point at 1,2
puts p.x  # => 1
# create a circle
c = Circle.new(4,5,6)
# copy it
d = c.dup
d.r = 7.5
puts c  # => Circle at 4,5 with radius 6
puts d  # => Circle at 4,5 with radius 7.5

[edit] Seed7

Seed7 object orientation works via interfaces. The example below introduces the interface type GraphicObj. To be usable an interface type needs also interface functions (which are defined with the keyword DYNAMIC). The interface function print is defined for GraphicObj. The struct types Point and Circle implement the the interface GraphicObj (they are implementation types). Note that Circle inherits x and y from Point. Functions which return a Point respectively Circle are used as constructors. Note that a Seed7 constructor does not need to have the name of the type (a new Point could be created with a function called abc). Seed7 defines copy constructor, assignment and destructor automatically.

$ include "seed7_05.s7i";
 
const type: GraphicObj is new interface;
 
const proc: print (in GraphicObj: aGraphicObj) is DYNAMIC;
 
 
const type: Point is new struct
var integer: x is 0;
var integer: y is 0;
end struct;
 
type_implements_interface(Point, GraphicObj);
 
const func Point: Point (in integer: x, in integer: y) is func
result
var Point: newPoint is Point.value;
begin
newPoint.x := x;
newPoint.y := y;
end func;
 
const proc: print (in Point: aPoint) is func
begin
writeln("Point(" <& aPoint.x <& ", " <& aPoint.y <& ")");
end func;
 
 
const type: Circle is sub Point struct
var integer: r is 0;
end struct;
 
type_implements_interface(Circle, GraphicObj);
 
const func Circle: Circle (in integer: x, in integer: y, in integer: r) is func
result
var Circle: newCircle is Circle.value;
begin
newCircle.x := x;
newCircle.y := y;
newCircle.r := r;
end func;
 
const proc: print (in Circle: aCircle) is func
begin
writeln("Circle(" <& aCircle.x <& ", " <& aCircle.y <& ", " <& aCircle.r <& ")");
end func;
 
 
const proc: main is func
local
var Point: pnt is Point(1, 2);
var Circle: circ is Circle(3, 4, 5);
var GraphicObj: graph is Point.value;
begin
graph := pnt;
print(graph);
graph := circ;
print(graph);
end func;
Output:
Point(1, 2)
Circle(3, 4, 5)

[edit] SIMPOL

In SIMPOL any type can be declared to be tagged with a name. That name can then be used to define a variable that can hold a reference to any type tagged with the same name. Multiple constructors are not needed, since all the parameters can be provided in the same constructor call. Types embedded in other types resolve according to the rules in SIMPOL such that if a property name is used that is not present in the actual type definition, then a depth first search starting at the beginning of the type definition will resolve a matching property or method name of an embedded type. This resolution is not performed on properties defined as reference are not used in the extended dot operator resolution mechanism unless they are also assigned the resolve keyword. The embed keyword in the type definition states that the type itself can be embedded in another type (any type can be placed as a reference in another type).

type mypoint(mypoint) embed export
embed
integer x
integer y
 
reference
function copy
function print
end type
 
 
function mypoint.new(mypoint me, integer x=0, integer y=0)
me.x = x
me.y = y
end function me
 
 
function mypoint.copy(mypoint me)
mypoint p
 
p =@ mypoint.new(me.x, me.y)
end function p
 
 
function mypoint.print(mypoint me)
end function "mypoint"
 
 
type circle(mypoint) embed export
reference
mypoint midpoint resolve
 
embed
integer radius
 
reference
function copy
function print
end type
 
 
function circle.new(circle me, integer x=0, integer y=0, integer radius=0, mypoint midpoint)
if midpoint =@= .nul
me.midpoint =@ mypoint.new(x, y)
else
me.x = midpoint.x
me.y = midpoint.y
end if
 
me.radius = radius
end function me
 
 
function circle.copy(circle me)
circle c
 
c =@ circle.new(radius=me.radius, midpoint=me.midpoint)
end function c
 
 
function circle.print(circle me)
end function "circle"
 
 
function main()
type(mypoint) p, c
string result
 
p =@ mypoint.new()
c =@ circle.new()
 
result = p.print() + "{d}{a}" + c.print() + "{d}{a}"
end function result

SIMPOL does not currently have access to stdin, stdout, and stderr, so to return a value from the program to a console, it must be as part of the return value.

[edit] Smalltalk

Like Python and Ruby, these objects do not need to be related in order to have polymorphic methods.

!Object subclass: #Point
instanceVariableNames: 'x y'
classVariableNames: ''
poolDictionaries: ''
category: 'polymorphism' !
 
!Point class methodsFor: 'instance creation'!
new
^self newBasic x := 0; y := 0 ! !
 
!Point class methodsFor: 'instance creation'!
x: x y: y
^self newBasic x := x; y := y ! !
 
!Point methodsFor: 'member access'!
x
^x ! !
 
!Point methodsFor: 'member access'!
y
^y ! !
 
!Point methodsFor: 'member access'!
x: x
^self x := x ! !
 
!Point methodsFor: 'member access'!
y: y
^self y := y ! !
 
!Point methodsFor: 'member access'!
x: x y: y
^self x := x; y := y ! !
 
!Point methodsFor: 'polymorphism test'!
print
Transcript show: x; space; show: y ! !
 
!Object subclass: #Circle
instanceVariableNames: 'center r'
classVariableNames: ''
poolDictionaries: ''
category: 'polymorphism' !
 
!Circle class methodsFor: 'instance creation'!
new
^self newBasic center := Point new; r := 0 ! !
 
!Circle class methodsFor: 'instance creation'!
radius: radius
^self newBasic center := Point new; r := radius ! !
 
!Circle class methodsFor: 'instance creation'!
at: point radius: r
^self newBasic center := point; r := r ! !
 
!Circle methodsFor: 'member access'!
center
^center ! !
 
!Circle methodsFor: 'member access'!
x: x y: y
^self center x: x y: y ! !
 
!Circle methodsFor: 'member access'!
radius
^r ! !
 
!Circle methodsFor: 'member access'!
radius: radius
^self r := radius ! !
 
!Circle methodsFor: 'polymorphism test'!
print
Transcript show: center; space; show: radius ! !

TODO: more idiomatic mechanism for presenting objects as strings. TODO: fill in more methods

[edit] Swift

class RCPoint : Printable {
var x: Int
var y: Int
init(x: Int = 0, y: Int = 0) {
self.x = x
self.y = y
}
convenience init(p: RCPoint) {
self.init(x:p.x, y:p.y)
}
var description: String {
return "<RCPoint x: \(self.x) y: \(self.y)>"
}
}
 
class RCCircle : RCPoint {
var r: Int
init(p: RCPoint, r: Int = 0) {
self.r = r
super.init(x:p.x, y:p.y)
}
init(x: Int = 0, y: Int = 0, r: Int = 0) {
self.r = r
super.init(x:x, y:y)
}
convenience init(c: RCCircle) {
self.init(x:c.x, y:c.y, r:c.r)
}
override var description: String {
return "<RCCircle x: \(x) y: \(y) r: \(r)>"
}
}
 
println(RCPoint())
println(RCPoint(x:3))
println(RCPoint(x:3, y:4))
println(RCCircle())
println(RCCircle(x:3))
println(RCCircle(x:3, y:4))
println(RCCircle(x:3, y:4, r:7))
let p = RCPoint(x:1, y:2)
println(RCCircle(p:p))
println(RCCircle(p:p, r:7))
println(p.x) // 1
p.x = 8
println(p.x) // 8

[edit] Tcl

Works with: Tcl version 8.6
or
Library: TclOO

Since Tcl's objects have their methods invoked by sending a (potentially-interceptable) message to them, allowing them to even respond to method calls that are not explicitly declared on them, there is no need for the objects to be formally related. We only do so here for convenience. In addition, Tcl's arguments to commands, procedures and methods are all fully polymorphic by default.

package require TclOO
oo::class create Point {
variable X Y
constructor {x y} {
set X $x
set Y $y
}
method x args {
set X {*}$args
}
method y args {
set Y {*}$args
}
method print {} {
puts "Point($X,$Y)"
}
method copy {} {
set copy [oo::copy [self]]
$copy x $X
$copy y $Y
return $copy
}
}
oo::class create Circle {
superclass Point
variable R
constructor {x y radius} {
next $x $y
set R $radius
}
method radius args {
set R {*}$args
}
method print {} {
puts "Circle([my x],[my y],$R)"
}
method copy {} {
set copy [next]
$copy radius $R
return $copy
}
}
# No destructors: unneeded by these classes
 
set p [Point new 1.0 2.0]
set c [Circle new 3.0 4.0 5.0]
set cCopy [$c copy]
puts "$p is at ([$p x],[$p y])"
$c radius 1.5
set objects [list $p $c $cCopy]
foreach o $objects {
$o print
}

[edit] zkl

Written for brevity

class Point{var x,y;
fcn init(xyOrPoint=0,_=0){
if(Point.isInstanceOf(xyOrPoint)) set(xyOrPoint);
else x,y=vm.arglist.apply("toFloat")}
fcn set(p){x=p.x;y=p.y}
fcn toString{"(%d,%d)".fmt(x,y)}
}
class Circle{var center, radius;
fcn init(a=0.0,b=0.0,r=1.0){
switch [arglist]{
case(Circle){ center=Point(a.center); radius=a.radius }
case(Point) { center=Point(a); radius=b.toFloat(); }
else { center=Point(a,b); radius=r.toFloat(); }
}
}
fcn copy{self(self)}
fcn toString{"(%s,%d)".fmt(center.toString(),radius)}
}
// see if various constructors work
Point(); Point(1); Point(1,2), Point(Point());
Circle(); Circle(1); Circle(1,2); Circle(1,2,3);
Circle(Point()); Circle(Point(),1);
Circle(Circle());
 
c:=Circle(1,2,3);
c.println(); c.center.println();
c.copy().println();
Output:
((1,2),3)
(1,2)
((1,2),3)
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