chapter 3 - functions.pptx

7/25/2019 Chapter 3 - Functions.pptx

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2000 Prentice Hall, Inc. All rights reserved.

1

Chapter 3 - Functions

Outline

3.1Introduction3.2Program Components in C++3.3Math Library Functions3.4Functions3.5Function Definitions3.6Function Prototypes

3.7Header Files3.8Random Number Generation3.9Example: A Game of Chance and Introducingenum3.10Storage Classes3.11Scope Rules3.12Recursion3.13Example Using Recursion: The Fibonacci Series3.14Recursion vs. Iteration3.15Functions with Empty Parameter Lists


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2

Chapter 3 - Functions

Outline

3.16Inline Functions3.17References and Reference Parameters3.18Default Arguments3.19Unary Scope Resolution Operator3.20Function Overloading3.21Function Templates


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3

3.1 Introduction

Divide and conuer Construct a progra! "ro! s!aller pieces or

co!ponents

#ach piece !ore !anagea$le than the original progra!


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%

3.2 Program Components in C++

Progra!s &ritten $' co!$ining ne& "unctions &ith (prepac)aged*

"unctions in the C++standard li$rar'.

he standard li$rar' provides a rich collection

o" "unctions. Inputoutput getline, read etc./

Co!!on !athe!atical calculations po&, srt, ep,

etc./

tring !anipulationsstrcp', strcat, etc. an' !ore


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Functions are invo)ed $' a "unction call

A "unction call speci"ies the "unction na!e andprovides in"or!ation as argu!ents/ that the called

"unction needs

4oss to &or)er analog'5

A boss (the calling function or caller) asks a worker(the called function) to perform a task and return

(i.e., report back) the results when the task is done.


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6


Function de"initions 7nl' &ritten once

hese state!ents are hidden "ro! other "unctions.

4oss to &or)er analog'5

The boss does not know how the worker gets the jobdone; he just wants it done


7/732000 Prentice Hall, Inc. All rights reserved.

8

3.3 Math Library Functions

ath li$rar' "unctions Allo& the progra!!er to per"or! co!!on !athe!atical

calculations

Are used $' including the header "ile

Functions called $' &ritingfunctionNameargument/

#a!plecout



9

3.3 Math Library Functions

Function argu!ents can $e Constants

sqrt( 4 );

:aria$les

sqrt( x );

#pressionssqrt( sqrt( x ) );

sqrt( 3 - 6x );



no&n onl' in the "unction in &hich the' are de"ined

All varia$les declared in "unction de"initions are local

varia$les

Parameters ?ocal varia$les passed &hen the "unction is called that

provide the "unction &ith outside in"or!ation



10

3.5 Function Definitions

Create custo!i=ed "unctions to a)e in data

Per"or! operations

@eturn the result

Format for function definition:

return-value-type function-name parameter-list/

declarations and statements

B

Example:int square( int y)

return y ! y;

"



Outline11# $$ %i&. 3.3' i&0303.c**

+ $$ ,reatin& and usin& a *ro&rammer-deinedunction3 include4

/ intsquare( int); $$ unction *rototy*e9#0 intmain()## #+ or( intx #; x



12

3.6 Function Prototypes

Function protot'pe Function name

Parameters

In"or!ation, the "unction ta)es in

%eturntype

'pe o" in"or!ation the "unction passes $ac) to caller de"ault int/ oidsigni"ies the "unction returns nothing

7nl' needed i" "unction de"inition co!es a"ter the "unction

call in the progra!

#a!ple5int maximum( int5 int5 int );

a)es in 3 ints

@eturns an int

Note that it is enou&h to mention

'ust the data(typeof the input

parameters in the function

prototype

int maximum( int x5 int y5 int );

)owever! it is o* to mention the

variable namesas well



Outline13

1. Function prototype(3 parameters)

2. Input values

2.1 Call function

# $$ %i&. 3.4' i&0304.c**

+ $$ %indin& the maximum o three inte&ers

3 include

4 intmaximum( int5 int5 int); $$ unction*rototy*e

6 intmain()

/ inta5 b5 c;

9

#0 cout



Outline

+/

1%

3.Function definition

Program Output

#9 $$ %unction maximum deinition

+0 $$ x5 y and belo8 are *arameters to

+# $$ the maximum unction deinition++ intmaximum( intx5 inty5 int )

+3

+4 intmax x;+

+6 i( y > max )

+ max y;

+9 i( > max )

30 max ;3#

3+ returnmax;

33 "

7nter three inte&ers' ++ / #

aximum is' /

7nter three inte&ers' 9+ 3 #4aximum is' 9+

7nter three inte&ers' 4 #9 9/aximum is' 9/

+nitially! maxis equal to x

+f yis &reater than max!

ybecomes the new maxnow

Finally! if ,is &reater than max!

,becomes the new max

1



1

3.7 Header Files

Header "iles Contain "unction protot'pes "or li$rar' "unctions

?oad &ith include #a!ple5

,, etc.

Custo! header "iles De"ined $' the progra!!er

ave as ilename.h

?oaded into progra! using

include 2ilename.h2

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16

3.8 Random Number Generation

rand"unctioni rand();

enerates a pseudorando! nu!$er $et&een0and :=usuall' 32868/

A pseudorando! nu!$er is a preset seuence o" rando! nu!$ers

he sa!e seuence is generated upon ever' progra! eecution

?oad srand"unction

Eu!ps to a seeded location in a rando! seuence

srand( seed );srand( time( 0 ) ); $$must include

time( 0 ) he ti!e at &hich the progra! &as co!piled

Changes the seed ever' ti!e the progra! is co!piled, there$'

allo&ing randto generate rando! nu!$ers

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18

3.8 Random Number Generation

caling @educes rando! nu!$er to a certain range

odulus ?/ operator @educes nu!$er $et&een 0 and:=to a nu!$er

$et&een 0 and the scaling "actor

#a!ple

i rand() ? 6 1 #;

enerates a nu!$er $et&een #and 6

19# $$ %i 3 i 03 0



Outline19

1. Define loop

2.Output randomnumber

Program Output

# $$ %i&. 3.' i&030.c**+ $$ @hited5 scaled inte&ers *roduced by # 1 rand()? 63 include

4

/ include9

#0 include

##

#+ intmain()

#3

#4 or( inti #; i



Outline10; i--) n n!i;

returnn;

"intmain()

cout


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3.13Example Using Recursion: TheFibonacci Series

Fi$onacci series5 0, 1, 1, 2, 3, , 9... #ach nu!$er su! o" t&o previous ones

#a!ple o" a recursive "or!ula5

ib(n) ib(n-#) 1 ib(n-+)

C++ code "or ibonacci"unctionlon&ibonacci( lon&n )

i( n 0 NN n # ) $$ base case

returnn;

elsereturnibonacci( n - # ) 1 ibonacci( n O + );

"

%

313ExampleUsingRecursion:The


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Diagra! o" Fi$onnaci "unction

f( 3 )

f( 1 )f( 2 )

f( 1 ) f( 0 ) return 1

return 1 return 0

return +

+return

%6

313ExampleUsingRecursion:The


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Diagra! o" Fi$onnaci "unction

f( 3 )

f( 1 )f( 2 )

f( 1 ) f( 0 ) return 1

return 1 return 0

return +

+return

Outline%8# $$ %i&. 3.#' i&03#.c**

+ $$ : i ib i ti


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Outline+ $$ :ecursie ibonacci unction3 include

4 unsi&ned lon& ibonacci( unsi&ned lon&); intmain()6

unsi&ned lon&result5 number;/9 cout


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Outline

Program Output

%ibonacci(0) 07nter an inte&er' #%ibonacci(#) #7nter an inte&er' +%ibonacci(+) #

7nter an inte&er' 3%ibonacci(3) +

7nter an inte&er' 4%ibonacci(4) 3

7nter an inte&er' %ibonacci()

7nter an inte&er' 6%ibonacci(6) /

7nter an inte&er' #0%ibonacci(#0)

7nter an inte&er' +0%ibonacci(+0) 667nter an inte&er' 30%ibonacci(30) /3+040

7nter an inte&er' 3%ibonacci(3) 9++46

%


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3.14Recursion vs. Iteration

@epetition Iteration5 eplicit loop

@ecursion5 repeated "unction calls

er!ination Iteration5 loop condition "ails

@ecursion5 $ase case recogni=ed

4oth can have in"inite loops

4alance $et&een per"or!ance iteration/ and good

so"t&are engineering recursion/

0


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3.15Functions with Empty Parameter Lists

#!pt' para!eter lists #ither &riting oidor leaving a para!eter list e!pt'

indicates that the "unction ta)es no argu!ents

oid *rint();

or

oid *rint( oid ); Function*rintta)es no argu!ents and returns no value

Outline1$$ %unctions that taPe no ar&uments


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Outline

1. Function prototypes(take noarguments)

2. Call the functions

3.Function definitions

Program Output

include

oidunction#();

oidunction+( oid);

intmain()

unction#();

unction+();

return0;

"

oidunction#()

cout


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3.16Inline Functions

inline"unctions @educe "unction-call overhead As)s the co!piler to cop' code into progra! instead

o" using a "unction call Co!piler can ignore inline hould $e used &ith s!all, o"ten-used "unctions

#a!ple 15inline double cube( const double s )

return s ! s ! s; "

#a!ple 2inline int max(int a5 int b)

return (a > b) H a ' b;

"

3


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3.17References and Reference Parameters

Call $' value

Cop' o" data passed to "unction Changes to cop' do not change original

sed to prevent un&anted side e""ects

Call $' re"erence Function can directl' access data

Changes a""ect original

@e"erence para!eter alias "or argu!ent Qis used to signi"' a re"erence

oid chan&e( int Qariable )

ariable 1 3; " Adds 3 to the varia$le inputted

int Qy x.

A change to y&ill no& a""ect xas &ell


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Using a Reference Parameter

+s li*e &ivin& someone the *ey

to your home

The *ey can be used by the

other person to chan&e the

contents of your homeC

Dain Pro&ram Demory


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Dain Pro&ram Demory

25

4000

age

If you pass a copyof ageto a function, it is called

pass-by-alue!and t"e function #ill not be able

to c"ange t"e contents of age in t"e calling

bloc$% it is still 25 #"en you &etu&n

'(), if you pass 4000, t"e add&ess of age to a

function, it is called pass-by-&efe&enceand t"efunction #ill be able to c"ange t"e contents of

age in t"e calling bloc$% it could be 23 o& 90 #"en

you &etu&n


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Additional Terms

Pass(by(reference

is also called - - -pass-$'-address, or

pass-$'-location

+an you eplain why-


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Pass-by-value

*+I.'/*

(*)I/

*+

incoing!

alue of

a&guent


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Pass-by-reference

*+I.'/* (*)I/

*+

incoing!

o&iginal alue of

a&guent

outgoing!

c"anged alue of

a&guent/,


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Pass-by-reference

*+I.'/* (*)I/

*+

/ a&guent

"as no alue yet

#"en call occu&s

outgoing!

ne# alue of

a&guent

Outline60$$ ,om*arin& call-by-alue and call-by-reerence

$$ ith

Lotice the use o" theQ operator


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1. Function prototypes

1.1 Initialize variables

2. Printx

2.1 Call function andprintx

2.2 Print

2.3 Call function andprint

3. Function Definition of

squareJyGalue

$$ 8ith reerences.

include

intsquareJyGalue( int);

oidsquareJy:eerence( intQ );

intmain()

intx +5 4;

cout


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3.1 Function Definition ofsquareJy:eerence

Program Outputx + beore squareJyGalueGalue returned by squareJyGalue' 4x + ater squareJyGalue 4 beore squareJy:eerence #6 ater squareJy:eerence

c:e ! c:e; $$ callerSs ar&ument modiied"

Outline


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Example of Pass-by-Reference

Ge want to find " real roots for aquadratic equation with coefficients

a!b!c- Grite a prototype for a void

function named Het%oots./ with parameters

are type float- The last " are

reference parameters of type float-

Outline


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void GetRoots(float, float, float,

float&, float&);

Now write the function definition usin& this information

This function uses > incomin& values a! b! c from the

callin& bloc*- +t calculates " out&oin& values root

and root" for the callin& bloc*- They are the " real

roots of the quadratic equation with coefficients a! b!

c-

&ototype

Outline


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void GetRoots(float a, float b, float c,

float& root1, float& root2)

{

float temp; // Local variable

temp = b * b - 4.0 * a * c;

root1 =(-b + sqrt(temp)) /(2.0 * a);

root2 =(-b - sqrt(temp)) /(2.0 * a);

return;

}

Function Iefinition

64

6

318DefaultArguments


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3.18Default Arguments

I" "unction para!eter o!itted, gets de"ault

value Can $e constants, glo$al varia$les, or "unction calls

I" not enough para!eters speci"ied, right!ost go to

their de"aults et de"aults in "unction protot'pe

int deault%unction( int x #5

int y +5 int 3 );

Outline66$$ %i&. 3.+3' i&03+3.c**

$$ Dsin& deault ar&uments


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+0

1. Function prototype

2. Print default volume

2.1 Print volume withone parameter

2.2 Print with 2parameters

2.3 Print with allparameters.

3. Function definition

include

intboxGolume(intlen&th#5int8idth#5inthei&ht#);intmain()

cout


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Program Output

Bhe deault box olume is' #Bhe olume o a box 8ith len&th #058idth # and hei&ht # is' #0Bhe olume o a box 8ith len&th #058idth and hei&ht # is' 0Bhe olume o a box 8ith len&th #058idth and hei&ht + is' #00

Lotice ho& the right!ost

values are de"aulted.

69

320FunctionOverloading


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3.20Function Overloading

Function overloading

Having "unctions &ith sa!e na!e and di""erent para!eters hould per"or! si!ilar tas)s i.e., a "unction to suare

ints, and "unction to suare loats/.

int square( int x) return x ! x;"

loat square(loat x) return x ! x; " Progra! chooses "unction $' signature

signature deter!ined $' "unction na!e and para!eter t'pes

Can have the sa!e return t'pes

Outline6


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1. Define overloadedfunction

2. Call function

Program Output

3 include

4

usin&std''cout;

6 usin&std''endl;

/ intsquare( intx ) returnx ! x; "

9

#0 doublesquare( doubley ) returny ! y; "

##

#+ intmain()

#3

#4 cout


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3.19Unary Scope Resolution Operator

nar' scope resolution operator ''/ Access glo$al varia$les i" a local varia$le has sa!e na!e not needed i" na!es are di""erent

instead o" ariableuse ''ariable

Outline81

$$ %i&. 3.+4' i&03+4.c**


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1. Define variables

2. Print variables

Program Output

$$ Dsin& the unary sco*e resolution o*erator

include

include

const doubleKC 3.#4#9+63/99;

intmain()

const loatKC staticcast< loat>( ''KC );

cout


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3.21Function Templates

Function te!plates

Co!pact &a' to !a)e overloaded "unctions >e'&ord tem*late >e'&ord classor ty*ename$e"ore ever' "or!al t'pe

para!eter $uilt in or user de"ined/

tem*late < class B >

$$ or tem*late< ty*ename B >B square( B alue# )

return alue# ! alue#;

" Breplaced $' t'pe para!eter in "unction call.

int x;

int y square(x); I" int, all BNs $eco!e ints

Can use loat, double, lon&...


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// function template

#include templateclassT;

T HetDax .T a! T b/ ?

T result

result = .a;b/J a : b

return.result/

A

intmain ./ ?

inti =

n = HetDax long;.l ! m/

cout * endl

dl

chapter 3 - functions.pptx

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