Fundamentals of Programmingce.sharif.edu/courses/93-94/1/ce153-1/resources/root/Slides/Sessio… · Fall 2014 Instructor: Reza Entezari-Maleki Email: [email protected] 1 Sharif

Fall 2014

Instructor: Reza Entezari-Maleki

Email: [email protected]

Sharif University of Technology 1

Fundamentals of Programming Session 27

These slides have been created using Deitel’s slides

Outlines

Constructors

Destructors

When Constructors and Destructors Are Called

Default Memberwise Assignment

Union

Introducing enum

File Processing

Data Hierarchy

Files and Streams

Creating a Sequential-Access File

2

Constructors

Initialize data members

Or can set later

Same name as class

No return type

Initializers

Passed as arguments to constructor

In parentheses to right of class name before semicolon

Class-type ObjectName( value1,value2,…);

3

Constructors

4

1 // Member functions for class SalesPerson.

2 #include <iostream>

3 #include <iomanip>

4 using namespace std;

5 // class definition

6 class SalesPerson {

7 public:

8 SalesPerson(); // constructor

9 void getSalesFromUser(); // input sales from keyboard

10 void setSales( int, double ); // set sales for a month

11 void printAnnualSales(); // summarize and print sales

12 private:

13 double totalAnnualSales(); // utility function

14 double sales[ 12 ]; // 12 monthly sales figures

15 }; // end class SalesPerson

5

16 SalesPerson::SalesPerson()

17 {

18 for ( int i = 0; i < 12; i++ )

19 sales[ i ] = 0.0;

20 } // end SalesPerson constructor

21 // get 12 sales figures from the user at the keyboard

22 void SalesPerson::getSalesFromUser()

23 {

24 double salesFigure;

25 for ( int i = 1; i <= 12; i++ ) {

26 cout << "Enter sales amount for month " << i << ": ";

27 cin >> salesFigure;

28 setSales( i, salesFigure );

29 } // end for

30 } // end function getSalesFromUser

31 // set one of the 12 monthly sales figures; function subtracts

32 // one from month value for proper subscript in sales array

6

33 void SalesPerson::setSales( int month, double amount )

34 {

35 // test for valid month and amount values

36 if ( month >= 1 && month <= 12 && amount > 0 )

37 sales[ month - 1 ] = amount; // adjust for subscripts 0-11

38 else // invalid month or amount value

39 cout << "Invalid month or sales figure" << endl;

40 } // end function setSales

41 // print total annual sales (with help of utility function)

42 void SalesPerson::printAnnualSales()

43 {

44 cout << setprecision( 2 ) << fixed

45 << "\nThe total annual sales are: $"

46 << totalAnnualSales() << endl; // call utility function

47 } // end function printAnnualSales

48 // private utility function to total annual sales

7

49 double SalesPerson::totalAnnualSales()

50 {

51 double total = 0.0; // initialize total

52 for ( int i = 0; i < 12; i++ ) // summarize sales results

53 total += sales[ i ];

54 return total;

55 } // end function totalAnnualSales

56 int main()

57 {

58 SalesPerson s; // create SalesPerson object s

59 s.getSalesFromUser(); // note simple sequential code; no

60 s.printAnnualSales(); // control structures in main

61 return 0;

62 } // end main

8

Enter sales amount for month 1: 5314.76












The total annual sales are: $60120.59

Constructors

Can specify default arguments

Default constructors

Defaults all arguments

OR

Explicitly requires no arguments

Can be invoked with no arguments

Only one per class

9

Constructors …

10


2 #include <iomanip>


4

5 classTime {

6 public:

7 Time( int = 0, int = 0, int = 0); // default constructor

8 void setTime( int, int, int ); // set hour, minute, second

9 void printUniversal(); // print universal-time format

10 void printStandard(); // print standard-time format

11 private:

12 int hour; // 0 - 23 (24-hour clock format)

13 int minute; // 0 - 59

14 int second; // 0 - 59

15 }; // end class Time

11

// ensures all Time objects start in a consistent state

16 Time::Time( int hr, int min, int sec )

17 {

18 setTime( hr, min, sec ); // validate and set time

19 } // end Time constructor

20 // set new Time value using universal time, perform validity

21 // checks on the data values and set invalid values to zero

22 voidTime::setTime( int h, int m, int s )

23 {

24 hour = ( h >= 0 && h < 24 ) ? h : 0;

25 minute = ( m >= 0 && m < 60 ) ? m : 0;

26 second = ( s >= 0 && s < 60 ) ? s : 0;

27 } // end function setTime

28 // print Time in universal format

29 voidTime::printUniversal()

30 {

31 cout << setfill( '0' ) << setw( 2 ) << hour << ":"

32 << setw( 2 ) << minute << ":"

33 << setw( 2 ) << second;

34 } // end function printUniversal

12

30 // print Time in standard format

31 voidTime::printStandard()

32 {

33 cout << ( ( hour == 0 || hour == 12 ) ? 12 : hour % 12 )

34 << ":" << setfill( '0' ) << setw( 2 ) << minute

35 << ":" << setw( 2 ) << second

36 << ( hour < 12 ? " AM" : " PM" );

37

38 } // end function printStandard

13

7 int main()

8 {

9 Time t1; // all arguments defaulted

10 Time t2( 2 ); // minute and second defaulted

11 Time t3( 21, 34 ); // second defaulted

12 Time t4( 12, 25, 42 ); // all values specified

13 Time t5( 27, 74, 99 ); // all bad values specified

14 cout << "Constructed with:\n\n"

15 << "all default arguments:\n ";

16 t1.printUniversal(); // 00:00:00

17 cout << "\n ";

18 t1.printStandard(); // 12:00:00 AM

14

19 cout << "\n\nhour specified; default minute and second:\n ";


21 cout << "\n ";


23 cout << "\n\nhour and minute specified; default second:\n ";


25 cout << "\n ";

26 t3.printStandard(); // 9:34:00 PM

27 cout << "\n\nhour, minute, and second specified:\n ";


29 cout << "\n ";

30 t4.printStandard(); // 12:25:42 PM

31 cout << "\n\nall invalid values specified:\n ";


33 cout << "\n ";


35 cout << endl;

36 return 0;

37 } // end main

15

Constructed with:

all default arguments:

00:00:00

12:00:00 AM

hour specified; default minute and second:

02:00:00

2:00:00 AM

hour and minute specified; default second:

21:34:00

9:34:00 PM

hour, minute, and second specified:

12:25:42

12:25:42 PM

all invalid values specified:

00:00:00

12:00:00 AM

Destructors

Special member function

Same name as class

Preceded with tilde (~)

No arguments

No return value

Cannot be overloaded

No explicit destructor

Compiler creates “empty” destructor

16

Destructors

Constructors and destructors

Called implicitly by compiler

Order of function calls

Depends on order of execution

When execution enters and exits scope of objects

Generally, destructor calls reverse order of constructor calls

17

Destructors …

Order of constructor, destructor function calls

Global scope objects Constructors

Before any other function (including main)

Destructors

When main terminates (or exit function called)

Not called if program terminates with abort

Automatic local objects Constructors

When objects defined

o Each time execution enters scope

Destructors

When objects leave scope

o Execution exits block in which object defined

Not called if program ends with exit or abort18

When Constructors and Destructors Are Called

Order of constructor, destructor function calls

static local objects

Constructors

Exactly once

When execution reaches point where object defined

Destructors

When main terminates or exit function called

Not called if program ends with abort

19

When Constructors and Destructors Are Called …

20



3 // Definition of class CreateAndDestroy.

4 class CreateAndDestroy {

5 public:

6 CreateAndDestroy( int, char * ); // constructor

7 ~CreateAndDestroy(); // destructor

8 private:

9 int objectID;

10 char *message;

11 }; // end class CreateAndDestroy

12 // constructor

13 CreateAndDestroy::CreateAndDestroy(

14 int objectNumber, char *messagePtr )

15 {

16 objectID = objectNumber;

17 message = messagePtr;

18 cout << "Object " << objectID << " constructor runs "

19 << message << endl;

20 } // end CreateAndDestroy constructor

21

21 // destructor

22 CreateAndDestroy::~CreateAndDestroy()

23 {

24 // the following line is for pedagogic purposes only

25 cout << ( objectID == 1 || objectID == 6 ? "\n" : "" );

26

27 cout << "Object " << objectID << " destructor runs "

28 << message << endl;

29

30 } // end ~CreateAndDestroy destructor

31

32 void create( void ); // prototype

33 // global object

34 CreateAndDestroy first( 1, "(global before main)" );

35 int main()

36 {

37 cout << "\nMAIN FUNCTION: EXECUTION BEGINS" << endl;

38 CreateAndDestroy second( 2, "(local automatic in main)" );

39 static CreateAndDestroy third(

40 3, "(local static in main)" );

22

41 create(); // call function to create objects

42 cout << "\nMAIN FUNCTION: EXECUTION RESUMES" << endl;

43 CreateAndDestroy fourth( 4, "(local automatic in main)" );

44 cout << "\nMAIN FUNCTION: EXECUTION ENDS" << endl;

45 return 0;

46 } // end main

47 // function to create objects

48 void create( void )

49 {

50 cout << "\nCREATE FUNCTION: EXECUTION BEGINS" << endl;

51 CreateAndDestroy fifth( 5, "(local automatic in create)" );

52 static CreateAndDestroy sixth(

53 6, "(local static in create)" );

54 CreateAndDestroy seventh(

55 7, "(local automatic in create)" );

56 cout << "\nCREATE FUNCTION: EXECUTION ENDS\" << endl;

57 } // end function create

23

Object 1 constructor runs (global before main)

MAIN FUNCTION: EXECUTION BEGINS

Object 2 constructor runs (local automatic in main)

Object 3 constructor runs (local static in main)

CREATE FUNCTION: EXECUTION BEGINS

Object 5 constructor runs (local automatic in create)

Object 6 constructor runs (local static in create)

Object 7 constructor runs (local automatic in create)

CREATE FUNCTION: EXECUTION ENDS

Object 7 destructor runs (local automatic in create)

Object 5 destructor runs (local automatic in create)

MAIN FUNCTION: EXECUTION RESUMES

Object 4 constructor runs (local automatic in main)

MAIN FUNCTION: EXECUTION ENDS

Object 4 destructor runs (local automatic in main)

Object 2 destructor runs (local automatic in main)

Object 6 destructor runs (local static in create)

Object 3 destructor runs (local static in main)

Object 1 destructor runs (global before main)

Assigning objects

Assignment operator (=)

Can assign one object to another of same type

Default: memberwise assignment

Each right member assigned individually to left member

Passing, returning objects

Objects passed as function arguments

Objects returned from functions

Default: pass-by-value

Copy of object passed, returned

Copy constructor

o Copy original values into new object24

Default Memberwise Assignment

25

1 // Demonstrating that class objects can be assigned

2 // to each other using default memberwise assignment.


4 using std::cout;

5 using std::endl;

6 // class Date definition

7 class Date {

8 public:

9 Date( int = 1, int = 1, int = 1990 ); // default constructor

10 void print();

11 private:

12 int month;

13 int day;

14 int year;

15 }; // end class Date

26

16 // Date constructor with no range checking

17 Date::Date( int m, int d, int y )

18 {

19 month = m;

20 day = d;

21 year = y;

22 } // end Date constructor

23 // print Date in the format mm-dd-yyyy

24 void Date::print()

25 {

26 cout << month << '-' << day << '-' << year;

27 } // end function print

28 int main()

29 {

30 Date date1( 7, 4, 2002 );

31 Date date2; // date2 defaults to 1/1/1990

27

32 cout << "date1 = ";

33 date1.print();

34 cout << "\ndate2 = ";

35 date2.print();

36 date2 = date1; // default memberwise assignment

37 cout << "\n\nAfter default memberwise assignment, date2 = ";

38 date2.print();

39 cout << endl;

40 return 0;

41 } // end main

date1 = 7-4-2002

date2 = 1-1-1990

After default memberwise assignment, date2 = 7-4-2002

Union

Memory that contains a variety of objects

Data members share space

Only contains one data member at a time

Only the last data member defined can be accessed

Declaration same as class or structunion Number {

int x;

float y;

};

Numebr myObject;

28

Union

29

1 // Fig. 20.8: fig20_08.cpp

2 // An example of a union.


4 using std::cout;

5 using std::endl;

6 // define union Number

7 union Number {

8 int integer1;

9 double double1;

10 }; // end union Number

11 int main()

12 {

13 Number value; // union variable

14 value.integer1 = 100; // assign 100 to member integer1

15 cout << "Put a value in the integer member\n"

16 << "and print both members.\nint: "

17 << value.integer1 << "\ndouble: " << value.double1

18 << endl;

30

19 value.double1 = 100.0; // assign 100.0 to member double1

20 cout << "Put a value in the floating member\n"

21 << "and print both members.\nint: "

22 << value.integer1 << "\ndouble: " << value.double1

23 << endl;

24 return 0;

25 } // end main

Put a value in the integer member

and print both members.

int: 100

double: -9.25596e+061

Put a value in the floating member

and print both members.

int: 0

double: 100

31

1 // Fig. 20.9: fig20_09.cpp

2 // Using an anonymous union.


4 using std::cout;

5 using std::endl;

6 int main()

7 {

8 // declare an anonymous union

9 // members integer1, double1 and charPtr share the same space

10 union {

11 int integer1;

12 double double1;

13 char *charPtr;

14 }; // end anonymous union

15 // declare local variables

16 int integer2 = 1;

17 double double2 = 3.3;

18 char *char2Ptr = "Anonymous";

32

19 // assign value to each union member

20 // successively and print each

21 cout << integer2 << ' ';

22 integer1 = 2;

23 cout << integer1 << endl;

24

25 cout << double2 << ' ';

26 double1 = 4.4;

27 cout << double1 << endl;

28

29 cout << char2Ptr << ' ';

30 charPtr = "union";

31 cout << charPtr << endl;

32 return 0;

33 } // end main

1 2

3.3 4.4

Anonymous union

Enumeration

Set of integers with identifiers

enum typeName {constant1, constant2…};

Constants start at 0 (default), incremented by 1

Constants need unique names

Cannot assign integer to enumeration variable

Must use a previously defined enumeration type

Exampleenum Status {CONTINUE, WON, LOST};

Status enumVar;

enumVar = WON; // cannot do enumVar = 1

33

Introducing enum

Enumeration constants can have preset values

enum Months { JAN = 1, FEB, MAR, APR,

MAY, JUN, JUL, AUG, SEP, OCT, NOV,

DEC};

Starts at 1, increments by 1

Next: craps simulator

Roll two dice

7 or 11 on first throw: player wins

2, 3, or 12 on first throw: player loses

4, 5, 6, 8, 9, 10

Value becomes player's "point"

Player must roll his point before rolling 7 to win34

Introducing enum …

35

1 // Fig. 3.10: fig03_10.cpp

2 // Craps.


4 using std::cout;

5 using std::endl;

6 // contains function prototypes for functions srand and rand

7 #include <cstdlib>

8 #include <ctime> // contains prototype for function time

9 int rollDice( void ); // function prototype

10 int main()

11 {

12 // enumeration constants represent game status

13 enum Status { CONTINUE, WON, LOST };

14 int sum;

15 int myPoint;

16 Status gameStatus; // can contain CONTINUE, WON or LOST

36

17 // randomize random number generator using current time

18 srand( time( 0 ) );

19 sum = rollDice(); // first roll of the dice

20 // determine game status and point based on sum of dice

21 switch ( sum ) {

22 // win on first roll

23 case 7:

24 case 11:

25 gameStatus = WON;

26 break;

27 // lose on first roll

28 case 2:

29 case 3:

30 case 12:

31 gameStatus = LOST;

32 break;

37

33 // remember point

34 default:

35 gameStatus = CONTINUE;

36 myPoint = sum;

37 cout << "Point is " << myPoint << endl;

38 break; // optional

39 } // end switch

40 // while game not complete ...

41 while ( gameStatus == CONTINUE ) {

42 sum = rollDice(); // roll dice again

43 // determine game status

44 if ( sum == myPoint ) // win by making point

45 gameStatus = WON;

46 else

47 if ( sum == 7 ) // lose by rolling 7

48 gameStatus = LOST;

49 } // end while

38

50 // display won or lost message

51 if ( gameStatus == WON )

52 cout << "Player wins" << endl;

53 else

54 cout << "Player loses" << endl;

55 return 0; // indicates successful termination

56 } // end main

57 // roll dice, calculate sum and display results

58 int rollDice( void )

59 {

60 int die1;

61 int die2;

62 int workSum;

63 die1 = 1 + rand() % 6; // pick random die1 value

64 die2 = 1 + rand() % 6; // pick random die2 value

65 workSum = die1 + die2; // sum die1 and die2

39

66 // display results of this roll

67 cout << "Player rolled " << die1 << " + " << die2

68 << " = " << workSum << endl;

69 return workSum; // return sum of dice

70 } // end function rollDice

Player rolled 2 + 5 = 7

Player wins


Player loses


Point is 6





Player wins

40


Point is 4









Player loses

Storage of data

Arrays, variables are temporary

Files are permanent

Magnetic disk, optical disk, tapes

41

File Processing

From smallest to largest

Bit (binary digit)

1 or 0

Everything in computer ultimately represented as bits

Cumbersome for humans to use

Character set

Digits, letters, symbols used to represent data

Every character represented by 1's and 0's

Byte: 8 bits

Can store a character (char)

42

Data Hierarchy

From smallest to largest (continued)

Field: group of characters with some meaning

Your name

Record: group of related fields

struct or class in C++

Each field associated with same employee

Record key: field used to uniquely identify record

File: group of related records

Sequential file: records stored by key

Database: group of related files

43

Data Hierarchy …

44

Data Hierarchy …

1

01001010

Judy

Judy Green

Sally Black

Tom Blue

Judy Green

Iris Orange

Randy Red

File

Record

Field

Byte (ASCII character J)

Bit

C++ views file as sequence of bytes

Ends with end-of-file marker

When file opened

Object created, stream associated with it

cin, cout, etc. created when <iostream> included

Communication between program and file/device

45

Files and Streams

0 31 2 4 5 8 9

...

... n-1

end-of-file marker

6 7

C++ imposes no structure on file

Concept of "record" must be implemented by programmer

To open file, create objects

Classes

ifstream (input only)

ofstream (output only)

fstream (I/O)

Constructors take file name and file-open modeofstream outClientFile( "filename", fileOpenMode );

To attach a file laterOfstream outClientFile;

outClientFile.open( "filename", fileOpenMode);

46

Creating a Sequential-Access File

File-open modes

ofstream opened for output by default ofstream outClientFile( "clients.dat", ios::out );

ofstream outClientFile( "clients.dat");

47

Creating a Sequential-Access File …

Mode Description

ios::app Write all output to the end of the file.

ios::in Open a file for input.

ios::out Open a file for output.

ios::binary Open a file for binary (i.e., non-text) input or

output.

Operations

Overloaded operator!

!outClientFile

Returns nonzero (true) if badbit or failbit set

Opened non-existent file for reading, wrong permissions

Operations

Writing to file (just like cout)

outClientFile << myVariable

Closing file

outClientFile.close()

Automatically closed when destructor called

48

Creating a Sequential-Access File …

Fundamentals of Programmingce.sharif.edu/courses/93-94/1/ce153-1/resources/root/Slides/Sessio… · Fall 2014 Instructor: Reza Entezari-Maleki Email: [email protected] 1 Sharif

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