OOP Chapter2

8/9/2019 OOP Chapter2

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Understand the concept of Classes and Objects

Use Constructor in Program

Use Destructor in Program

Create classes and function as a friend

Create overloaded method and overloaded operator

Write program using Templates

2.1

2.2

2.3

2.4

2.5

2.6


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Define Class

Define Method

Access Specifier

Declare Objects

1

2

3

4


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General format for defining a class :

class ClassName{

// Data definition

// Method definition};

**TIPS**

*Keywordclass is a must in defining a class.

* Semicolon (;) must be placed after closing braces each time

you define a class.


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class Rectangle

{ int length, width;

public :

void set_data (int x,int y)

{ length=x;

width=y;

}

double calculate_area()

{ return length*width;}

};

Method definition

ClassName

Data member definition

Keyword for defining a class

Access

control


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There are two ways of defining method :

1. Define it in the class

class Student{int ID,age;

char name[30];double mark;

public:void set_data (int a,int b, char * c, double d){

ID=a;age=b;strcpy(name,c);mark=d;}};


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2. Define it outside the class by using scope resolution operator (::)

class Student{int ID,age;char name[30];double mark;

public:void set_data (int a,int b,char * c,double d);

};

void Student::set_data(int a,int b,char * c,double d){

ID=a;age=b;strcpy(name,c);

mark=d;}

declare

define


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Three type of access specifier for data members and

methods:

1. Public

2. Private3. Protected


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1. Public

Public members are accessible outside the class (for example

in main() function).

Members in the class must be declared in the public section to

make it accessible from outside the class.

Definition of friend does not give any effect to this access control.

class AccessCtrl{int value1;void func1 (long);int value2;int func2 (char*);

public :char* value4;long func4 ( );

};


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2.Private Private members can only be achieved by functional members

and friends for a class, whichhas been declared.

Example of the use of this keyword in the real world:

The ATM pin number, password to open an e-mail.

This example is more appropriate if it is declared privately so that it

is not accessed by any other unauthorized person.

class AccessCtrl{

int value1;

int value2;int func2 (char*);void func1 (long);

};

Private Data

Private Method


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1. Protected

Protected members are accessible in

the class where it is declared and also

any other classes, which are inherited

from that class. Definition of friend does not give any

effect to this access control.

Example of the use of this keyword in

the real world:

Total savings for a student.

Only certain people knows the actualtotal savings by a student

such as his/her family members.

class A{ protected:

int valueA;};class B : public A

{ public:void FuncB( );

};class C : public B{

public:void FuncC( );

};


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Syntax:

Assuming that you have created an object from the class Student.

Example of declaration is shown as below:

Student p;

When an object has been declared, it can be manipulated by any

function, which is declared inside the object class.

Syntax is used to call a data or method:

ObjectName . MemberName

dot operator

className objectName;


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Define Constructor

Characteristics of Constructor

Types of Constructors

(Use Constructors in Program)

1

2

3


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1. A constructor is a member (method/function) that is

called automatically each time when an object is created.

2. The constructor allocates sufficient memory space for

the object.

3. C++ will automatically supply a constructor if it is

not supplied.


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Constructorhas the same name as the class.

For example constructor for class Employee is declared as:

class Employee{public:

Employee ( ); /* pengisytiharanconstructor */};

Nama kelas

Nama method

constructor

The constructors task is to built and create object in

memory. However a constructor does not return a value.

An argument can be sent to the constructor

The constructor is called automatically when an object is

created.This means, we dont have to invoke it like other

functions.


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1.Default Constructor

2.Parameterized Constructor

3.Initialization Constructor

4.Copy Constructor

5.Overloading Constructor


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1.Default Constructor

1. Does not require any value (parameter).

2. Only have to declare the object.

3. C++ will automatically supply a constructor if it is not supplied.

Secara automatik,

pengisytiharan objek ini akan

menyebabkan aturcara

memperuntukkan ruang

memori untuk objek box1.Untuk mewujudkan beberapa

objek, kelas harus mempunyai

constructorlalai.

NOTA

#include

class box {private:

float length, width;public:box ( ); // defaultconstructorvoid input( );

void area ( );};void main(){

boxbox1; // pengistiharan kelas}

Method constructortidak menerima sebarang nilai


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2.Parameterized Constructor

1. A constructor can have many parameters.

2. If the constructor receives a parameter, when the object is created the

parameter must be included with the declaration of the object.

#includeclass SegiEmpat{int panjang,lebar;

public:SegiEmpat(int a, int b):panjang(a),lebar(b){}int kira_luas(){return panjang * lebar;}

};void main(){int m,n;coutm;coutn;SegiEmpat S(m,n);cout


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3.Initialization Constructor

1. The value is entered after an argument list for function, starting

with single point ( : )

class SegiEmpat{protected:

int panjang,lebar;

public:// method constructor

SegiEmpat ():panjang(10),lebar(20){}};

y Data panjang akan diberikan nilai 10 manakala nilai data lebar akan diberikan

nilai 20.

y { } masih diperlukan.


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The example of a program is to calculate the area of a rectangle based

on the value given on method constructor.

#includeclass SegiEmpat{

int panjang,lebar;public:SegiEmpat():panjang(10),lebar(20){}

int kira_luas(){return panjang * lebar;

}};void main(){SegiEmpat a;cout


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4.Copy Constructor

1. Changing the private data value through a constructor.

SegiEmpat a (1,2);SegiEmpat b(a);

Objek b akan menyalin nilai yang

dimiliki oleh objek a

#include

class SegiEmpat{int panjang,lebar;public:SegiEmpat(int a, int b):panjang(a),lebar(b){}int kira_luas(){return panjang * lebar;}};

void main(){int m,n;coutm;coutn;SegiEmpat S(m,n);SegiEmpat Z(S);cout


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1. Just like other methods, constructor can also be

overloaded.

2. You only have to list down all the different version of

constructor needed to be used in the class.

3. The main purpose of overloading a constructor is to

provide options or give the object initial value or not.

4. For example, in the following program, o1 will begiven initial value but not foro2.


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#includeclass SegiEmpat_Sama{

int panjang ;public:SegiEmpat_Sama ( ) { panjang = 5; }SegiEmpat_Sama ( int n ) { panjang=n;}int luas(){return panjang*panjang;}};int main(){

SegiEmpat_Sama o1(10); /* isytiharkanobjek dengan nilai awalan */

SegiEmpat_Sama o2; /* isytiharkantanpa nilai Awalan */

cout


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Define Destructors

Types of Destructors

Use Destructors in Program

1

2

3


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1. The destructor is a function that is called automaticallywhen an object is destroyed or goes out of scope.

2. The destructor reclaims the memory that is allocated to

the object.


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1. A destructorhas the same name as the class, but it has a

tilde (~) in front of it.

2. A destructor does not return a value.

3. Unlike a constructor, you cannot pass any argument to adestructor.

4. You cannot have more than one destructor for each

class.

5. A destructor is called automatic when an object goes out

of scope.That means, you dont have to invoke it like

other functions.


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#includeclass SegiEmpat{int panjang,lebar;public:SegiEmpat();

~SegiEmpat();

int kira_luas(){return panjang * lebar;}

};void main(){SegiEmpat a;cout


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Define friend

Declare a friend

Declaring function as a friend

Declaring class as a friend

1

2

4

3


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1. A function or class can be defined as a friend to otherclasses

2. If a function or class becomes the friend to another

class, for example class or function Abecomes the

friend to class C, class or function A can access privatemember of class C.

3. This concept is considered important to apply if there is

a situation, which we want a class or function wants to

access the private data from the class.


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1. The declaration for friend can be done throughnumerous ways:

I. Declaring function as the friend

II. Declaring class as the friend

The keyword friend should be placed in front of the function

or class, which wants to announce as the friend in the class.

For example, if the function calculate() as the friend to Maths

class, so the announcement of a friend should be done inthe Maths class.


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1. By placing th

e keyword friend in front of th

e functions name, th

e functioncan achieve private member of the class.The declaration of friend function

is done in public.

2. The program below stated is an example of the mean for function, which

become friend for staff class.

class pekerja {// ..public:friend void kira_gaji( pekerja a);//.}

Example: Function void count_salary();

which has become the friend for the class

staff. By this declaration, this function can

achieve private member; which is staff

class.


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The example below shows how the calculation of area for the

rectangle is made using friend.

Ahli kelas SegiEmpat yang

disimpan ditempat yang sulit(data-data private)

Kelas SegiEmpatFungsi

Kira_Luas

Pengawal keselamatan akan memeriksa sama ada fungsi Kira_luas berhak

atau tidak mencapai data-data dari kelas SegiEmpat dan jika fungsi

kira_luas diisytiharkan sebagai rakan oleh kelas SegiEmpat, maka ia boleh

mencapai data-data dari kelas SegiEmpat.


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#include

class SegiEmpat{int panjang,lebar;

public:SegiEmpat(int a,int b){panjang=a;lebar=b;}friend int Kira_Luas(SegiEmpat x);};int Kira_Luas(SegiEmpat x){return x.panjang * x.lebar; }

void main(){int a, b;

couta;coutb;SegiEmpat tepat(a,b);cout


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1. To make a class as a friend for another class, declaration

of a friend has to be done on a prototype class.

2. Declaration of friend has to been done using keyword

friend.

3. Example below shows how class square was declared as

a friend to class shape.

class bentuk{friend class segiempat;..

public:..};class segiempat

{private:.

public:};

Shape class

declared class

Square as a friend

to class Shape. This

means the class

Square can achieve

private member forclass Shape.

.


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Below is an example which shows class markah_pelajar becomes

friend to class info_pelajar to enable data memberinfo_pelajaraccess data member from class markah_pelajar.

#include #include

class markah_pelajar;

class info_pelajar {friend class markah_pelajar;

private:char nama[30],ic[10];

public:void setdata(char *,char *);

};void info_pelajar::setdata(char *a,char *b){ strcpy(nama,a);

strcpy(ic,b);}

class markah_pelajar{float markah1,markah2,jumlah;

public:void setmarkah(float,float);

void kiraMarkah();void paparan(info_pelajar);

};

voidmarkah_pelajar::setmarkah(floatujian1,

float ujian2){ markah1=ujian1;

markah2=ujian2;}


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void markah_pelajar::kiraMarkah()

{jumlah=markah1 + markah2;}void

markah_pelajar::paparan(info_pelajara){cout


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Output


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Definition of overloading function

Create overloading function

Rules of overloading function

Definition of operator overloading

Rules of operator overloading

Create overloaded operator

1

2

3

4

6

5


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1. Overloading function is a mechanism; which allows 2 ormore related function to share a same name but thedeclaration of parameter functions is different.

2. In this situation, the shared name of a function is called

overload and this process is referred as a function whichshows overloading

3. The function overloading is a method of C++ that appliespolymorphism concept during compiling.

4. The overloading function can reduce the difficulty of aprogram by allowing operation to be referred with thesame name.


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1. Declare all versions of the functions.

2. The compiler automatically with select the most

suitable version of the overloaded function based on

the argument used to call the function.

3. The example shows how the function name set() is

used with5 different versions:


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class ABC

{int a;char ab [10];char aks;float price;

public:void set (int x) //method 1{ a=x;}void set (char xy[10]) //method 2{ strcpy(ab,xy); }void set (char h) //method 3{ aks=h; }void set(float p) //method 4{ price =p; }void set ( int x, float y )//method 5{ a=x; price = y; }

::};

void main ( )

{ABC object1;object1.set(6);//pergi ke method 1object1.set(SIX);//pergi ke method 2object1.set (S);//pergi ke method 3object1.set (7.5);//pergi ke method 4object1.set (9,8.96);//pergi ke method 5::};


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The example below shows how the overloading function f() is overloaded

3 times with

different versions.

// Overload fungsi sebanyak 3kali

#include using namespace std;

void f(int i);//parameterberjenis

integervoid f (int i,int j);/* 2 parameter

berjenis

integer */

void f(double k);/*1 parameterberjenis

double */

int main(){f(10);//Memanggil f(int)f(10,20);//Memanggil f(int,int)f(12.23);//Memanggil f(double)return 0;}

Output

void f(int i){cout


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1. Different parameter:

The numbers of parameter received for each version must be different.

The type of parameter received must be different.

2. The example shown has an errorbecause the numbers and types of

parameter are the same.

The return data type can be same or different for overloading function.

/* Ini merupakan contohyangtidak

betul dan tidak kompil. */

int f1(int a);double f1(int a);..f1(10); // fungsiyangmana

pengkompil akan panggil?

Pengkompil tidak tahu f1( ) versi

yang mana satu perlu dipanggil.

NOTA


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1. Operator overloading and function overloading is similar.

2. According to the facts, the operator overloading is actually

part of function overloading.

3. When an operator is overload, the original meaning of theoperator is not lost.Besides that, it will have added meaning

to the class, which defines it.

4. Overloaded operatoruses overloading function:

Operator function is a member or a friend to class, which defines it.

The operator overloading function is different from friend function.


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1. Return value normally this function returns the type ofdeclared class (even though the free operator function canreturn any types of data)

2. The symbol # is placement for the operators that will beoverloaded (example: sign +,++,-,*).

3. The list of argument - depends on how the overloadingfunction is done.

Return value class-name :: operator # (list of argument)

{

// Operation to be done

}


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The example shown below will do the addition operation, deduction and

subtraction on 2 numbers, which are included in user.

#includeclass pilih{public:int x;pilih(){};

pilih(int a){x=a;}pilih operator +(pilih param){pilih jawapan;jawapan.x=x+param.x;return (jawapan);}pilih operator -(pilih param){

pilih jawapan;jawapan.x=x-param.x;return (jawapan);}pilih operator *(pilih param){pilih jawapan;jawapan.x=x*param.x;return (jawapan);}

};


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void main()

{int a,b;couta;coutb;pilih obj1(a);pilih obj2(b);

pilih obj3,obj4,obj5;obj3=obj1+obj2;//obj3=obj1.operator +(obj2)obj4=obj1-obj2;obj5=obj1*obj2;cout


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1. Two limitations of operator overloading:

The precedence of the operator cannot be changed.

The amount of operand (variables) for the operator cannot be changed even

though the operator function can neglect the operand if the function has an

overload operator /.This means that only one operand can be used.

2. The operator function cannot have default argument.

3. Most of the C++ operators can be overloaded except. :: . * ? and the

pre-process directive. ( .* is special operator).

4. You can use 2 overloading operators: >.This operator is

used in overloading process forI/O.

These operators are used forI/O processes, but this does not prevent the

operators from doing mathematical function/ task.


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Contoh di bawah menunjukkan operator ++ disaratkan terhadap kelas coord.

#include

class coord {int x,y;//nilai kordinatpublic:coord() { x=0;y=0;}coord(int i,int j) {x=i;y=j;}

void get_xy(int &i,int &j) { i=x;j=y;}coord operator++();};//overload ++ untuk kelas coord

coord coord::operator++(){x++;y++;return *this;}

int main(){coord o1(10,10);int x,y;++o1;//penambahan objekcout


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Contoh program yang mempunyai proses penyaratan unari pengurangan.

#include class numbers{int x,y,z;public:void get_data(int,int,int);void show_data();void operator-(); //saratkan operator unari};void numbers::get_data(int a,int b,int c){x=a;y=b;z=c;}void numbers::show_data(){cout


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void main(){

numbers num;//membina object

num.get_data(11,-22,33);

cout


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Define Template

Declare function templates

1

2


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1.Template can be assumed as one t

hat can be used todevelop a function or class.

2. C++ use template to achieve polymorphism that is during

compilation.

3. One example of template in real world is a cake mould.A

cake mould can be used for making a chocolate or fruit

cake.

Boleh digunakan

untuk membuat

Kek coklat

Kek buah

Acuan kek


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4. By using template, it allows programmer create genericfunction and generic class function.

5. Generic function is a draft for a function that can be used to

generate a few same functions in different version.

6. The advantages of a template are that coding can be shortened

and made easier. If using generic class, new classes can built

without coding the definition, only by using the current generic

class.


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1. You can define more than one generic data type in a template

statement by using coma (,) to separate generic data types.

2. The program given below used to compare 2 values.

#include

templatevoid perbandingan( banding1 x, banding2 y){

if (x>y)cout


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1. Wh

en you call generic function, argument of function willdetermine types of data that will be used in function.

2. However, C++ allows you to do pre-definition data types

by determining types of data that you want program to

manipulate.


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#include

template void luas(segi4 panjang, segi4 lebar){ segi4 segi;

segi= panjang * lebar;cout


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void main(){

int i=10,j=20;

double y=10.1,z=4.2;

cout


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template void luas(segi4

panjang, segi4 lebar){:}

luas(i,j) luas(y,z)

Nilai integer i dan j dihantar ke fungsi

generik yang mempunyai pra-takrifan

jenis data integer

Nilai integer y dan z dih

antarke fungsi generik yang umum

void luas(int i, int j){

:}

void luas(segi4 y, segi4 z){

:}


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1. Generic function is almost like an overloaded function except it has more

limitation.2. Generic function must do the same action for all version - only data types

can be different.

3. This program shows error when outdata() function do not do the same

thing.

void outdata (int i){cout


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1. When you create generic class, youbuilt class that

defines all algorithm used by class, but the actual data

types that is being manipulated will be specified as

parameter when object for the class is created.

2. Generic class is useful when class uses logical that can

be made as general conclusion.

3. Example: The same algorithm to maintain integer rows will

work for character rows.

4. When you create generic class, it can implement operation

that you defined.

5. Compiler will generate correct object types automatically;

based on types youve specified when object is created.


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6. Generic class definition begins with the keyword template followed by

parameter list for that template that written in < >. Then followed byidentifier that represents name of that generic class, and followed by

class members that written in {}.

7. Below is a general form for generic class.

template class

Nama_Kelas{::}

8. When youhave built generic class, youbuilt specific object for that

class by using a general form as below:Nama_Kelas

Nama_Objek;

DataType is data type that will be referred by the class during operation.


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do{coutpilihan;

switch(pilihan){case 1: {

pilihan = 1;coutukur1;coutukur2;segi4.Luas(1,ukur1,ukur2);

break;}

case 2:{pilihan= 2;coutukur1;coutukur2;cout


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Pilihan 1Segi4.luas(1,ukur1,ukur2)

Pilihan 2Segi3.luas(2,ukur1,ukur2

)

templateBentuk::Luas(type1 1,type1ukur1,

type1 ukur2){ if (pilihan ==1){

luas=ukur1 * ukur2;cout


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PENERANGAN

Dalam contoh aturcara ini, kelas generik bentuk digunakan untuk membentuk dua objek

iaitu objek segi3 dan objek segi4 melalui pernyataan :

Bentuksegi3;

Bentuksegi4;

Apabila pengguna memilih pilihan satu, segi4.luas(1, ukur1, ukur2) akan menghantar

argumen-argumen 1, ukur1 dan ukur2 ke dalam fungsi luas() yang terdapat dalamkelas generik bentuk dan memberi nilai 1 pada pembolehubah pilihan, nilai ukur1 pada

pembolehubah u1 dan nilai ukur2 pada pembolehubah u2.

Kemudian nilai-nilai argumen yang telah diberi nilai akan digunakan untuk mengira nilai

luas segiempat.

Hal yang sama akan dilakukan jika pengguna membuat pilihan dua di manasegi3.luas(2, ukur1.ukur2) akan menghantar argumen-argumennya ke dalam fungsi

luas() yang terdapat pada kelas generik bentuk untuk memberi nilai argumen-argumen

tersebut dengan pembolehubah yang ada pada fungsi luas() dan menggunakan nilai-

nilai yang diberi nilai untuk mengira luas segitiga pula.


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do {

cout pilih;switch(pilih){case 1:harga=10.00;break;

case 2:

harga=5.00;break;

default:cout


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#include templateclass Kira{

segi4 panjang, lebar;public:luas (segi4, segi4);

};template Kira ::luas(segi4 panjang, segi4 lebar){ segi4 segi;

segi= panjang * lebar;cout

Documents

OOP Chapter2