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Tuy nhiên, có thể sử dụng ép kiểu để chuyển đổi một con trỏ lớp cơ sở thành một con trỏ lớp dẫn xuất.

Ví dụ 5.1: Chương trình sau sẽ được chia thành nhiều file (gồm các file .H và .CPP) và tạo một project có tên là CT5_1.PRJ gồm các file .cpp

File POINT.H:

1: //POINT.H

2: //Định nghĩa lớp Point

3: #ifndef POINT_H

4: #define POINT_H

5:

6: class Point

7: {

8: protected:

9: float X,Y;

10: public:

11: Point(float A= 0, float B= 0);

12: void SetPoint(float A, float B);

13: float GetX() const

14: {

15: return X;

16: }

17: float GetY() const

18: {

19: return Y;

20: }

21: friend ostream&operator<<(ostream&Output, const Point&P);

22: };

23:

24: #endif

File POINT.CPP

1: //POINT.CPP

2: //Định nghĩa các hàm thành viên của lớp Point

3: #include<iostream.h>

4: #include "point.h"

5:

6: Point::Point(float A, float B)

7: {

8: SetPoint(A, B);

9: }

10:

11: void Point::SetPoint(float A, float B)

12: {

13: X = A;

14: Y = B;

15: }

16:

17: ostream&operator<<(ostream&Output, const Point&P)

18: {

19: Output<<'['<<P.X<<", "<<P.Y<<']';

20: return Output;

21: }

File CIRCLE.H

1: //CIRCLE.H

2: //Định nghĩa lớp Circle

3: #ifndef CIRCLE_H

4: #define CIRCLE_H

5:

6: #include "point.h"

7: class Circle : public Point

8: {

9: protected:

10: float Radius;

11: public:

12: Circle(float R = 0.0, float A = 0, float B = 0);

13: void SetRadius(float R);

14: float GetRadius() const;

15: float Area() const;

16: friend ostream&operator<<(ostream&Output, const Circle&C);

17: };

18:

19: #endif

File CIRCLE.CPP

1: //CIRCLE.CPP

2: //Định nghĩa các hàm thành viên của lớp Circle

3: #include<iostream.h>

4: #include<iomanip.h>

5: #include "circle.h"

6:

7: Circle::Circle(float R, float A, float B): Point(A, B)

8: {

9: Radius = R;

10: }

11:

12: void Circle::SetRadius(float R)

13: {

14: Radius = R;

15: }

16:

17: float Circle::GetRadius() const

18: {

19: return Radius;

20: }

21:

22: float Circle::Area() const

23: {

24: return 3.14159 * Radius * Radius;

25: }

26:

27: //Xuất một Circle theo dạng: Center = [x, y]; Radius = #.##

28: ostream&operator<<(ostream&Output, const Circle&C)

29: {

30: Output<<"Center = ["<<C.X<<", "<<C.Y

31:<<"]; Radius = "<<setiosflags(ios::showpoint)

32:<<setprecision(2)<<C.Radius;

33: return Output;

34: }

File CT5_1.CPP:

1: //CT5_1.CPP

2: //Chương trình 5.1: Ép các con trỏ lớp cơ sở tới các con trỏ lớp dẫn xuất

3: #include<iostream.h>

4: #include<iomanip.h>

5: #include "point.h"

6: #include "circle.h"

7:

8: int main()

9: {

10: Point *PointPtr, P(3.5, 5.3);

11: Circle *CirclePtr, C(2.7, 1.2, 8.9);

12: cout<<"Point P: "<<P<<endl<<"Circle C: "<<C<<endl;

13 //Xử lý một Circle như một Point (chỉ xem một phần lớp cơ sở)

14: PointPtr =&C;

15: cout<<endl<<"Circle C (via *PointPtr): "<<*PointPtr<<endl;

16 //Xử lý một Circle như một Circle

17: PointPtr =&C;

18: CirclePtr = (Circle *) PointPtr;

19: cout<<endl<<"Circle C (via *CirclePtr): "<<endl

20:           <<*CirclePtr<<endl<<"Area of C (via CirclePtr): "

21:           <<CirclePtr->Area()<<endl;

22: //Nguy hiểm: Xem một Point như một Circle

23: PointPtr =&P;

24: CirclePtr = (Circle *) PointPtr;

25: cout<<endl<<"Point P (via *CirclePtr): "<<endl

26:           <<*CirclePtr<<endl<<"Area of object CirclePtr points to: "

Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Lập trình hướng đối tượng. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10794/1.1
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