Functions in c++

Amity School of Engineering & Technology

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FUNCTIONS

Presented By:Shivani Dubey Priyanka YadavMaaz Hasan


CONTENTS• Introduction.• The Main Function.• Function Prototyping.• Call by Reference.• Return by Reference.• Inline Function.• Default Arguments.• Constant Arguments.• Recursion.• Function Overloading.• Friend and Virtual Function.• Math Library Function.

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INTRODUCTION• Divide and conquer :

– Construct a program from smaller pieces or components.

– These smaller pieces are called modules.

– Each piece more manageable than the original program.

– Building blocks of C++.

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• void show(); //function declaration

main()

{

….

show(); //function call

….

}

void show(); //function definition

{

… //function body

…

}

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AN EXAMPLE


THE MAIN FUNCTION

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• When a program begins running, the system calls the function main, which marks the entry point of the program.

• By default, main has the storage class extern.

• Every program must have one function named main, and the following constraints.


FUNCTION PROTOTYPING• A Function Prototype in C++ is a declaration of

a function that omits the function body but does specify the function's return type, name and argument types. While a function definition specifies what a function does, a function prototype can be thought of as specifying its interface.

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CALL BY REFERENCE• The Call by Reference method of passing arguments to a

function copies the reference of an argument into the formal parameter. Inside the function, the reference is used to access the actual argument used in the call. This means that changes made to the parameter affect the passed argument.

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AN EXAMPLE

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#include <iostream> using namespace std; // function declaration void swap(int &x, int &y); int main () { // local variable declaration: int a = 100; int b = 200; cout << "Before swap, value of a :" << a << endl; cout << "Before swap, value of b :" << b << endl; /* calling a function to swap the values using variable reference.*/ swap(a, b); cout << "After swap, value of a :" << a << endl; cout << "After swap, value of b :" << b << endl; return 0; }


RETURN BY REFERENCE• A C++ program can be made easier to read and maintain by

using references rather than pointers. A C++ function can return a reference in a similar way as it returns a pointer.

• When a function returns a reference, it returns an implicit pointer to its return value. This way, a function can be used on the left side of an assignment statement.

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INLINE FUNCTION• An Inline Function the programme

That has requested that the compiler insert

the complete body of the function in

every place that the function is called,

rather than generating code to call the

function in the one place it is defined.

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DEFAULT ARGUEMENTS

• In computer programming, a default argument is an argument to a function that a programmer is not required to specify. In most programming languages, functions may take one or more arguments.

• The default argument must be implicitly convertible to the parameter type.

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CONSTANT ARGUEMENTS• The const variable can be declared using const keyword.

• The const keyword makes variable value stable.

• The constant variable should be initialized while declaring.

Syntax:

• (a) const <variable name> = <value>;

• (b) <function name> (const <type>*<variable name>;)

• (c) int const x // in valid

• (d) int const x =5 // valid

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RECURSION• Recursive functions:

– Functions that call themselves

– Can only solve a base case

– Divide a problem up into

• What it can do.

• What it cannot do.

• What it cannot do resembles

• original problem.

• The function launches a new copy of itself (recursion step) to solve what it cannot do

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FUNCTION OVERLOADING• Function overloading is a feature found in that allows

creating several methods with the same name which differ from each other in the type of the input and the output of the function. It is simply defined as the ability of one function to perform different tasks.

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FRIEND & VIRTUAL FUNCTION

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• A Friend Function access to private and protected data in that class that it would not normally be able to as if the data was public.

• A Function of global or namespace scope may be declared as friend of both classes.

• A Virtual Function is a function or method whose behaviour can be overridden within an inheriting class by a function with the same signature. This concept is an important part of the polymorphism portion of Object-Oriented Programming (OOP).


MATH LIBRARY FUNCTION• C Mathematical Operations are a group of functions in

the Standard Library of the C programming language implementing basic mathematical functions.

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REFERENCES• Wikipedia.com.

• C++ By Yashwant Kanetkar.

• C++ By E Balagurusamy.

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