friend,overload,template

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OBJECT ORIENTED

PROGRAMMING(OOP)

POOBHARATHII A/L BALAKRISHNAN 19DIP09F2057

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CLASSES AND

FUNCTION AS A

FRIEND

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CREATE CLASSES AND

FUNCTION AS A FRIEND

a. Create a method or function of non-

member as a friends.

b. Create classes as a friend

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Definition of friend :

As in the real world

A function or class can be defined as a

friend to other classes Class becomes the friend to another class.

This concept is considered important to

apply if there is a situation, which we wanta class or function wants to access the

private data from the class

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A. A method or function of non-

member as a friends.

A friend function of a class is a member

function of the class, but has access to all

the member of the class.

The function want to being a friend to a

class, the reserved word friend precedes

the function prototype in the class

definition.

The word friends appear only the function

prototype in the class.

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Consider the followingConsider the following

statement:statement:Class class_IllusFriends

{

Friend void two (/*parameter*/)

..

....

};

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B. A function as a friend

By placing the keyword

friend in front of the

functions name, the

function can achieve private

member of the class.

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Declaring class as a friend

To make a class as a friend for

another class, declaration of a

friend has to be done on a

prototype class

Declaration of friend has tobeen done using keyword

friend

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ExampleExample below shows how class squarebelow shows how class square waswas

declareddeclared as aas a friend tofriend to classclass shapeshape classclass

ShapeShape

{

friend class Square;

..

public:

..};

class Square

{

private:.

public:

};

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OVERLOADED

METHOD

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Overload MethodAlso known as function polymorphism

The function will perform different operation

depends on argument list in the function call

a feature found in various programming

languages such as Ada, C#,VB .NET, C++, PHP, Dand Java

that allows the creation of several methods with

the same name which differ from each other in

terms of the

type of the input and the type of the output of

the function.

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Overloaded method based on program

situationpublic class AddingNumbers

{

public int Add(int a, int b)

{

return a+b;

}public int Add(int a, int b, int c)

{

return a+b+c;

}

}

Calling Overloaded Methods?

public int add(int x, int y)

public int add(int x, int y, int z)

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OVERLOADED

OPERATOR

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Operator overloading

In computer programming, operator overloading

(less commonly known as operator ad-hoc

polymorphism) is a specific case of polymorphism

in which some or all of operators like +, =, or ==have different implementations depending on the

types of their arguments.

Sometimes the overloading's are defined by the

language; sometimes the programmer can

implement support for new types.

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Operator overloading is claimed to be

useful because it allows the developer to

program using notation "closer to the

target domain"

allows user-defined types a similar level of

syntactic support as types built into the

language.

It can easily be emulated using function

calls;

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In a language that supports operator

overloading,

assuming the '* operator has higherprecedence than '+', this is effectively

a more concise way of writing:

add (a, multiply (b,c))

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Example:Time operator+(const Time& lhs, const Time& rhs) {

Time temp = lhs;temp.seconds += rhs.seconds;

if (temp.seconds >= 60) {

temp.seconds -= 60;

temp.minutes++;

}temp.minutes += rhs.minutes;

if (temp.minutes >= 60) {

temp.minutes -= 60;

temp.hours++;

}

temp.hours += rhs.hours;

return temp;

}

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Addition is a binary operation,

which means it has left and right

operands.

In C++, the arguments beingpassed are the operands, and the

temp object

is the returned value.

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Note that a unary operator defined as a class

method would receive no apparent argument (it

only works from this):

bool Time::operator!() const{

return ((hours == 0) && (minutes == 0)

&& (seconds == 0));

}

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TEMPLATES

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Define

Templates are a feature of the C++programming language that allowfunctions and classes to operate with

generic types. This allows a function or class to work on

many different data types without beingrewritten for each one.

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Declare Function Templates

With Parameter Format for declaring function templates with typeparameters is:

template function_declaration;

template function_declaration;

To use this function template we use the following

format for the function call:

function_name (parameters);

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Program using templates//function template

#include

using namespace std;

template

number integer ( number a)

{

number display;

display = a;

return (display);}

void main()

{

int a=10, c;

int w=5, y;

c=integer(a);y=integer(w);

cout

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