2009-12-04 |  RatheeshTR  | Viewed: 35  |    1

 
/*  A  base  class  of  Shape  gives  rise  to
two  derived  classes  -  Circle  and  Square.

An  application  called  Polygon  sets  up  an
array  of  Circles  and  Squares,  and  uses  a
getarea  method  to  find  the  area  of  each.

This  getarea  method  is  defined  as  a  virtual
method  in  the  base  class,  so  that  an  array
of  shapes  CAN  be  defined  on  which  two
different  getarea  methods  can  be  run
depending  on  which  type  of  shape  is  the
current  one  at  the  time.  */

::::::::::::::
shape.h
::::::::::::::

#ifndef SHAPE
#define SHAPE 1

class Shape {
        public:
                void setsize(int owbig);
                virtual float getarea() {};
        protected:
                int givensize;
        };

#endif
::::::::::::::
shape.cpp
::::::::::::::
#include "shape.h"

void Shape::setsize(int sv) {
        givensize = sv;
        }

::::::::::::::
square.h
::::::::::::::
#include "shape.h"

class Square: public Shape {
        public:
                float getarea();
        };
::::::::::::::
square.cpp
::::::::::::::
#include "square.h"

float Square::getarea() {
        float result = givensize * givensize;
        return (result);
        }
::::::::::::::
circle.h
::::::::::::::
#include "shape.h"

class Circle: public Shape {
        public:
                float getarea();
        };
::::::::::::::
circle.cpp
::::::::::::::
#include "circle.h"

float Circle::getarea() {
        float result = 3.14159265f * givensize;
        return result;
        }
::::::::::::::
polygon.cpp
::::::::::::::
#include <iostream.h>
#include "circle.h"
#include "square.h"

main () {

        int np = 10;
        Shape *jigsaw[np];

        for (int k=0; k<np; k+=2) {
                jigsaw[k] = new Square();
                jigsaw[k+1] = new Circle();
        }
        for (int k=0; k<np; k++) {
                jigsaw[k]->setsize(10+k);
                }
        for (int k=0; k<np; k++) {
                float syze = jigsaw[k]->getarea();
                cout << "this is sq " << syze << endl;
                }

        return (0);
        }

Reference:
//http://www.wellho.net/resources/ex.php4?item=c234/PMdemo