1 Review (Week2) - Control Structures C++ has only seven control structures: –Sequence structure...

Review (Week2) - Control Structures

C++ has only seven control structures:– Sequence structure

• Programs executed sequentially by default– Selection structures

•if, if/else, switch – Repetition structures

•while, do/while, for

What is the value of sum after completion of this loop?

sum = 0;for(i= -5; i <=1; i++) { sum = sum -i; }(a) 1(b) 14(c) -14(d) –15

If c is equal to 6, which of the following will be printed after execution of the following code?

cout << ( x == 7 ? “correct” : “incorrect” );

(a) 6(b) 7(c) correct(d) incorrect

Review (Week3) - Function

FunctionsPrepackaged functions: from the standard libraryprogrammer-defined functions

Function DefinitionsFunction Prototypes

Header Files

Recursion

References and Reference Parameters

51 // Fig. 3.4: fig03_04.cpp

2 // Finding the maximum of three integers

3 #include <iostream>

5 using std::cout;

6 using std::cin;

7 using std::endl;

9 int maximum( int, int, int ); // function prototype

11 int main()

13 int a, b, c;

15 cout << "Enter three integers: ";

16 cin >> a >> b >> c;

18 // a, b and c below are arguments to

19 // the maximum function call

20 cout << "Maximum is: " << maximum( a, b, c ) << endl;

Function definition

Comma separate list of arguments;

Data type needed for each argument;

Data type of result returned.

Program Output

22 return 0;

25 // Function maximum definition

26 // x, y and z below are parameters to

27 // the maximum function definition

28 int maximum( int x, int y, int z )

30 int max = x;

32 if ( y > max )

33 max = y;

35 if ( z > max )

36 max = z;

38 return max;

Enter three integers: 22 85 17Maximum is: 85

Header Files

//file MyMain.cpp

#include <iostream>

#include “MyFunctions.h”

Int main (){

int ItemQuantity;double ItemPrice, Cost;

ItemQuantity = 20; ItemPrice = 2.5

Cost = CalCost(ItemQuantity, ItemPrice);

cout << “Total Cost is”<< Cost<<endl;

Return();}//end main() function

//file MyFunctions.h

Double CalCost(int Quantity, double Price);

//file MyFunction.cpp

#include “MyFunctions.h”

Double CalCost(int Quantity, double Price)

double Cost;

Cost = Quantity * Price;

reture Cost;

Example: Random Number Generation

• Scaling– Reduces random number to a certain range– Modulus ( % ) operator

• Reduces number between 0 and RAND_MAX to a number between 0 and the scaling factor

– Example

i = rand() % 6 + 1;• Generates a number between 1 and 6

1. Define loop

2.Output random number

Program Output

1 // Fig. 3.7: fig03_07.cpp

2 // Shifted, scaled integers produced by 1 + rand() % 6

3 #include <iostream>

5 using std::cout;

6 using std::endl;

8 #include <iomanip>

10 using std::setw;

12 #include <cstdlib>

14 int main()

16 for ( int i = 1; i <= 20; i++ ) {

17 cout << setw( 10 ) << ( 1 + rand() % 6 );

19 if ( i % 5 == 0 )

20 cout << endl;

23 return 0;

Notice rand() % 6 . This returns a number between 0 and 5 (scaling). Add 1 to get a number between 1 and 6.

Executing the program again gives the same "random" dice rolls.

5 5 3 5 5 2 4 2 5 5 5 3 2 2 1 5 1 4 6 4

Program to roll dice

10Recursion

• Example: factorial (Mathematical formulas are often expressed recursively)

• Definition: 3! = 3*2*1 = 6

• Recursion expression:

3! = 3*2!

2! = 2*1! 1! = 1

• N! can be expressed recursively as:

N! = N * (N-1)! recursive case

1! = 1 base case

• The factorial is defined in terms of another factorial until the base case of 1! is reached

Recursion

A recursive solution to the factorial problem is defined by the following function called factorial:

int factorial (int number)

//base case

if (number == 1)

return 1;

//Recursive step

return number * factorial (number - 1);

1.4 If r = 5, what is value returned by fibo function?int fibo(int r){if(r == 0 || r== 1) return r;elsereturn fibo(r-1) + fibo( r - 2);}(a) 0(b) 2(c) 3(d) 5

References and Reference Parameters

3 ways to pass arguments to functions - 2 considered here and a third later

Pass by value: Input values from calling function are not changed on return from called function

Copy of data passed to functionChanges to copy do not change originalUsed to prevent unwanted side effects

Pass by reference: Arguments are referenced by their address and changes to contents of these addresses means the values in calling function are changed

Function can directly access dataChanges affect original

Function arguments

#include <vcl\condefs.h>#include <iostream.h> //Args2.cpp

void SwapbyValue( float x, float y);void SwapbyReference( float &x, float &y);

int main(void){char screenoff;float a=1.0, b=2.0; cout << "a = " << a << " b = " << b << endl; SwapbyValue (a, b); cout <<" Swap by Value\n"; cout << "a = " << a << " b = " << b << endl; SwapbyReference (a, b); cout <<" Swap by Reference\n"; cout << "a = " << a << " b = " << b << endl; cin >> screenoff; return 0;}

void SwapbyValue( float x, float y){float tmp;tmp = x;x = y;y = tmp;}

void SwapbyReference( float &x, float &y){float tmp;tmp = x;x = y;y = tmp;}

Review (Week4) - Arrays

Arrays

Passing Arrays to Functions

Sorting Arrays

Searching Arrays: Linear Search and Binary Search

If array HourlyTemp has been declared as:

Int HourlyTemp[24]

the function call

modifyArray (HourlyTemp, 24 );

passes array HourlyTemp and its size to function modifyArray

C++ pass arrays to functions using simulated pass-by-reference --- the called function can modify the element values in the callers’ original arrays. The value of the name of the array is the address in the computer’s memory of the first element of the array.

Passing Arrays to Functions Function prototype

• The function header for function modefyArray might be written as:

void modifyArray (int b[], int arraySize );– take an integer array and a single integer;

– indicating that modifyArray expects to receive the address of an array of integers in parameter b and the number of array elements in parameter arraySize.

• Note the strange appearance if the function prototype for modifyArray

Void modifyArray (int [], int);

Names optional in prototype

• Arrays passed-by-reference – Functions can modify original array data

– Value of name of array is address of first element• Function knows where the array is stored

• Can change original memory locations

• Individual array elements passed-by-value– Like regular variables– square( myArray[3] );

Sorting Arrays

• Sorting data– is an Important computing application

– Virtually every organization must sort some data • Massive amounts must be sorted

• Bubble sort (sinking sort) – Several passes through the array

• Successive pairs of elements are compared

– If increasing order (or identical), no change

– If decreasing order, elements exchanged

– Repeat these steps for every element

– If there are n elements, only n-1 passes are needed to sort the n element and only n-1 comparisons are needed for each pass.

Sorting Arrays

• Example:– Go left to right, and exchange elements as necessary

• On the first pass, the largest value sink to the bottom element;

• ……

– Original: 3 4 2 7 6

– Pass 1: 3 2 4 6 7 (elements exchanged)

– Pass 2: 2 3 4 6 7

– Pass 3: 2 3 4 6 7 (no changes needed)

– Pass 4: 2 3 4 6 7

– Small elements "bubble" to the top (like 2 in this example)

Searching Arrays: Linear Search

• Search array for a key value• Linear search

– Compare each element of array with key value

– Useful for small and unsorted arrays• Inefficient

a[1], a[2], a[3], a[4], … , a[n-1], a[n] 2 6 4 8 89 37

Key(8)

compare with

Searching Arrays: Binary Search

• Binary search– Only used with sorted arrays

– Compare middle element with key• If equal, match found

• If key < middle

– Repeat search on first half of array

• If key > middle

– Repeat search on last half

– Very fast • At most N steps, where 2 > # of elements

• 30 element array takes at most 5 steps

2 > 30

Review (Week5) - Pointers and Strings

Pointer Variable

Calling Functions by Reference

Relationship Between Pointers and Arrays

Pointer

• Pointer variables– Contain memory addresses as values

– Normally, variable contains specific value (direct reference)

– Pointers contain address of variable that has specific value (indirect reference)

countPtr

600000500000

Pointer Declarations

– * indicates variable is pointer

int *myPtr;

declares pointer to int, pointer of type int *

– Multiple pointers require multiple asterisks

int *myPtr1, *myPtr2;

– Can declare pointers to any data type

float *floatPtr;

Calling Functions by Reference

• 3 ways to pass arguments to function– Pass-by-value

– Pass-by-reference with reference arguments

– Pass-by-reference with pointer arguments

• Arguments passed to function using reference arguments– Modify original values of arguments

Function arguments

#include <vcl\condefs.h>#include <iostream.h> //Args2.cpp

void SwapbyValue( float x, float y);void SwapbyReference( float *x, float *y);

int main(void){char screenoff;float a=1.0, b=2.0; cout << "a = " << a << " b = " << b << endl; SwapbyValue (a, b); cout <<" Swap by Value\n"; cout << "a = " << a << " b = " << b << endl; SwapbyReference (&a, &b); cout <<" Swap by Reference\n"; cout << "a = " << a << " b = " << b << endl; cin >> screenoff; return 0;}

void SwapbyValue( float x, float y){float tmp;tmp = x;x = y;y = tmp;}

void SwapbyReference( float *x, float *y){float tmp;tmp = *x;*x = *y;*y = tmp;}

Pointer Expressions and Pointer Arithmetic

• Pointer arithmetic– Increment/decrement pointer (++ or --)

– Add/subtract an integer to/from a pointer( + or += , - or -=)

– Pointers may be subtracted from each other

– Pointer arithmetic meaningless unless performed on pointer to array

• 5 element int array on a machine using 4 byte ints– vPtr points to first element v[ 0 ], which is at location 3000

vPtr = 3000

– vPtr += 2; sets vPtr to 3008vPtr points to v[ 2 ]

pointer variable vPtr

v[0] v[1] v[2] v[4]v[3]

3000 3004 3008 3012 3016location

Relationship Between Pointers and Arrays

• Array and Point may be used almost interchangeable

• Arrays and pointers closely related– Array name like constant pointer

– Pointers can do array subscripting operations

• Assume– int b[5];– int *bPtr;

bPtr = b; bPtr = &b[0];

&b[3] bPtr+3

Array name (without a subscript)is a pointer to the first element of the array.

Relationship Between Pointers and Arraysint b[]= {10,20,30,40};• Four notation for referring to array elements

– Array subscript notation b[n] e.g. b [0] = 10

b [1] = 20 b [2] = 30 b [3] = 40

– Point/offset notation where the pointer is array name*(b + n ) e.g. *(b + 0 ) = 10

*(b + 1 ) = 20 *(b + 2 ) = 30

*(b + 3 ) = 40– Pointer subscript notation

bPtr[n] e.g. bPtr[0] = 10 bPtr[1] = 20 bPtr[2] = 30 bPtr[3] = 40

– Point/offset notation*( bPtr + n ) e.g. *( bPtr + 0 ) = 10

*( bPtr + 1 ) = 20 *( bPtr + 2 ) = 30

*( bPtr + 3 ) = 40

Assuming a is an integer array of 7 items and aptr is a pointer to the array. Which of the following addresses the 4th item of the array? (a) a[4](b) *aptr(c) &a[3](d) *(aptr+4)

Review (Week6) - Classes andData Abstraction

Structure

Initializing Class Objects: Constructors

Structure Definitions

• Structures – Aggregate data types built using elements of other types

struct Time {

int hour;

int minute;

int second;

• Structure member naming– In same struct: must have unique names

– In different structs: can share name

• struct definition must end with semicolon

Structure tag

Structure members

Structure Definitions

• struct definition– Creates new data type used to declare variables

– Structure variables declared like variables of other types

– Examples:• Time timeObject;• Time timeArray[ 10 ]; • Time *timePtr;• Time &timeRef = timeObject;

Accessing Structure Members

• Member access operators– Dot operator (.) accesses a structure or a class members via

the variable name for the object or via a reference to the object.

cout << timeObject.hour;cout << timeRef.hour;

– Arrow operator (->) accesses a structure or a class members via pointer to object

cout << timePtr->hour;– timePtr->hour same as ( *timePtr ).hour

• Parentheses required– * lower precedence than .

36// example about structures#include <iostream>using namespace std;

struct movies { string title; int year;} ;

int main (){ movies mine; mine.title = "2001 A Space Odyssey"; mine.year = 1968;

cout << "My favorite movie is:\n "; cout << mine.title; cout << " (" << mine.year << ")\n";

return 0;}

My favorite movie is: 2001 A Space Odyssey (1968)

37// example: class constructor#include <iostream>using namespace std;

class CRectangle { int width, height; public: CRectangle (int=5,int=5); int area (void) {return (width*height);}};

CRectangle::CRectangle (int a, int b) { width = a; height = b;}

int main () { CRectangle recta (3,4); CRectangle rectb; CRectangle rectc(3); cout << "recta area: " << recta.area() << endl; cout << "rectb area: " << rectb.area() << endl; cout << "rectc area: " << rectc.area() << endl; return 0;}

recta area: 12

rectb area: 25

rectc area: 15

Review (Week7) - Classes Part II

Composition: Objects as Members of Classes

Dynamic Memory

static Class Members

Operator Overloading

39Dynamic Memory Management with Operators new and delete

To use pointers you much follow four steps: 1. Declare the pointer variable

Int *FredsPtr;

2. Reserve a space in memory for the valueFredsPtr = new int;

3. Assign a value for the pointer*FredsPtr = 30;

4. Use delete to free the memoryDelete FredsPtr;

Address Contents

0x8566fff7 ???

0x8566fff6 ???

0x8566fff5 ???

0x8566fff4 45

Contents

??? FredsPtr

Address Contents

0x8566fff7 ???

0x8566fff6 ???

0x8566fff5 ???

0x8566fff4 45

Contents

0x8566fff6 FredsPtr

Address Contents

0x8566fff7 ???

0x8566fff6 30

0x8566fff5 ???

0x8566fff4 45

Contents

0x8566fff6 FredsPtr

*FredsPtr

Address Contents

0x8566fff7 ???

0x8566fff6 ???

0x8566fff5 ???

0x8566fff4 45

Contents

??? FredsPtr

Dynamic Memory Management with Operators new and delete

• new1. Can declare and reserve a space in one line:

Int *FredsPtr = new int;

Int *FredsPtr;

FredsPtr = new int;

2. Providing initializersdouble *ptr = new double( 3.14159 );

Time *timePtr = new Time( 12, 0, 0 );

3. Allocating arraysint *gradesArray = new int[ 10 ];

Dynamic Memory Management with Operators new and delete

The NULL pointer Int main()

Int *FredsPtr = NULL;

if (FredsPtr = = NULL){ // if the pointer is NULL

FredsPtr = new int; //then create a new pointer

*FredsPtr = 30; //and give it a value

Address Contents

0x8566fff7 ???

0x8566fff6 30

0x8566fff5 ???

0x8566fff4 45

Contents

0x8566fff6 FredsPtr

*FredsPtr

Address Contents

0x8566fff7 ???

0x8566fff6 30

0x8566fff5 ???

0x8566fff4 45

Contents

NULL FredsPtr

42• #include <iostream> • using namespace std;• • int main () • {• int i,n; • int * p; • cout << "How many numbers would you like

to type? "; • cin >> i; • p= new int[i]; • if (p == 0)

cout << "Error: memory could not be allocated";

• else • {

for (n=0; n<i; n++) {

cout << "Enter number: "; cin >> p[n];

} • cout << "You have entered: "; • for (n=0; n<i; n++)

cout << p[n] << ", "; • delete[] p; • }• return 0; • }

How many numbers would you like to type? 5 Enter number : 75 Enter number : 436 Enter number : 1067 Enter number : 8 Enter number : 32 You have entered: 75, 436, 1067, 8, 32,

1. Declare the pointer variable

2. Reserve a space in memory for the value

3. Assign a value for the pointer

4. Use delete to free the memory

Operator Overloading

• Types– Built in (int, char) or user-defined

– Can use existing operators with user-defined types• Cannot create new operators

• Overloading operators– Create a function for the class

– Name function operator followed by symbol• Operator+ for the addition operator +

Operator Overloading• C++ incorporates the option to use standard operators to perform

operations with classes in addition to with fundamental types. For example:

int a, b, c; a = b + c;

This is obviously valid code in C++, since the different variables of the addition are all fundamental types.

• Nevertheless, it is not so obvious that we could perform an operation similar to the following one:

struct { string product; float price; } a, b, c; a = b + c;

In fact, this will cause a compilation error. However, we can design classes able to perform operations using standard operators.

45// vectors: overloading operators example#include <iostream>using namespace std;

class CVector { public: int x,y; CVector (int=0, int=0); CVector operator + (CVector);}; CVector::CVector (int a, int b) { x = a; y = b;} CVector CVector::operator+ (CVector param) { CVector temp; temp.x = x + param.x; temp.y = y + param.y; return (temp);} int main () { CVector a (3,1); CVector b (1,2); CVector c; c = a + b; cout << c.x << "," << c.y; return 0;}

CVector (int, int); // function name CVector (constructor) CVector operator+ (CVector); // function returns a CVector

c = a + b;

c = a.operator+ (b);

type operator sign (parameters) { /*...*/ }

46// operator_overloading.cpp#include <iostream>using namespace std;

class Complex{public: Complex( double r, double i ) : re(r), im(i) { }

Complex operator-( Complex &other ); void Display( ) { cout << re << ", " << im << endl; }private: double re, im;};

// Operator overloaded using a member functionComplex Complex::operator-( Complex &other ){return Complex( re - other.re, im - other.im );}

int main(){ Complex a = Complex( 1.2, 3.4 ); Complex b = Complex( 5.6, 7.8 ); Complex c = Complex( 0.0, 0.0 );

c = a - b; c.Display();}

-4.4, -4.4

c = a - b;

c = a.operator- (b);

Review (Week8) _Inheritance

Base Classes and Derived Classes

point3.h (1 of 1)

1 // Fig. 9.17: point3.h2 // Point3 class definition represents an x-y coordinate pair.3 #ifndef POINT3_H4 #define POINT3_H5 6 class Point3 {7 8 public:9 Point3( int = 0, int = 0 ); // default constructor10 11 void setX( int ); // set x in coordinate pair12 int getX() const; // return x from coordinate pair13 14 void setY( int ); // set y in coordinate pair15 int getY() const; // return y from coordinate pair16 17 void print() const; // output Point3 object18 19 private: 20 int x; // x part of coordinate pair21 int y; // y part of coordinate pair22 23 }; // end class Point324 25 #endif

Better software-engineering practice: private over protected when possible.

// default constructor

Point3::Point3( int xValue, int yValue )

: x( xValue ), y( yValue )

{ // empty body } // end Point3 constructor

point3.cpp (1 of 2)

1 // Fig. 9.18: point3.cpp2 // Point3 class member-function definitions.3 #include <iostream> 4 5 using std::cout;6 7 #include "point3.h" // Point3 class definition8 9 // default constructor10 Point3::Point3( int xValue, int yValue )11 : x( xValue ), y( yValue )12 {13 // empty body 14 15 } // end Point3 constructor16 17 // set x in coordinate pair18 void Point3::setX( int xValue )19 {20 x = xValue; // no need for validation21 22 } // end function setX23

Member initializers specify values of x and y.

point3.cpp (2 of 2)

24 // return x from coordinate pair25 int Point3::getX() const26 {27 return x;28 29 } // end function getX30 31 // set y in coordinate pair32 void Point3::setY( int yValue )33 {34 y = yValue; // no need for validation35 36 } // end function setY37 38 // return y from coordinate pair39 int Point3::getY() const40 {41 return y;42 43 } // end function getY44 45 // output Point3 object46 void Point3::print() const47 {48 cout << '[' << getX() << ", " << getY() << ']';49 50 } // end function print

Invoke non-private member functions to access private data.

circle4.h (1 of 1)

1 // Fig. 9.19: circle4.h2 // Circle4 class contains x-y coordinate pair and radius.3 #ifndef CIRCLE4_H4 #define CIRCLE4_H5 6 #include "point3.h" // Point3 class definition7 8 class Circle4 : public Point3 {9 10 public:11 12 // default constructor13 Circle4( int = 0, int = 0, double = 0.0 ); 14 15 void setRadius( double ); // set radius16 double getRadius() const; // return radius17 18 double getDiameter() const; // return diameter19 double getCircumference() const; // return circumference20 double getArea() const; // return area21 22 void print() const; // output Circle4 object23 24 private: 25 double radius; // Circle4's radius26 27 }; // end class Circle428 #endif

Class Circle4 inherits from class Point3.

Maintain private data member radius.

Circle4::Circle4( int xValue, int yValue, double radiusValue )

: Point3( xValue, yValue ) // call base-class constructor

setRadius( radiusValue );

void Circle4::setRadius( double radiusValue )

radius = ( radiusValue < 0.0 ? 0.0 : radiusValue );

circle4.cpp (1 of 2)

1 // Fig. 9.20: circle4.cpp2 // Circle4 class member-function definitions.3 #include <iostream> 4 5 using std::cout;6 7 #include "circle4.h" // Circle4 class definition8 9 // default constructor10 Circle4::Circle4( int xValue, int yValue, double radiusValue )11 : Point3( xValue, yValue ) // call base-class constructor12 {13 setRadius( radiusValue );14 15 } // end Circle4 constructor16 17 // set radius 18 void Circle4::setRadius( double radiusValue )19 {20 radius = ( radiusValue < 0.0 ? 0.0 : radiusValue );21 22 } // end function setRadius23 24 // return radius 25 double Circle4::getRadius() const26 {27 return radius;28 } // end function getRadius2930

Base-class initializer syntax passes arguments to base class Point3.

circle4.cpp (2 of 2)

31 // calculate and return diameter32 double Circle4::getDiameter() const33 {34 return 2 * getRadius();35 36 } // end function getDiameter37 38 // calculate and return circumference39 double Circle4::getCircumference() const40 {41 return 3.14159 * getDiameter();42 43 } // end function getCircumference44 45 // calculate and return area46 double Circle4::getArea() const47 {48 return 3.14159 * getRadius() * getRadius();49 50 } // end function getArea51 52 // output Circle4 object53 void Circle4::print() const54 {55 cout << "Center = ";56 Point3::print(); // invoke Point3's print function57 cout << "; Radius = " << getRadius();58 } // end function print

Invoke function getRadius rather than directly accessing data member radius.

Redefine class Point3’s member function print.

Invoke base-class Point3’s print function using binary scope-resolution operator (::).

Review (Week9) _Polymorphism

Relationships Among Objects in an Inheritance HierarchyInvoking Base-Class Functions from Derived-Class object

Virtual Functions

point.h (1 of 1)

1 // Fig. 10.8: point.h2 // Point class definition represents an x-y coordinate pair.3 #ifndef POINT_H4 #define POINT_H5 6 class Point {7 8 public:9 Point( int = 0, int = 0 ); // default constructor10 11 void setX( int ); // set x in coordinate pair12 int getX() const; // return x from coordinate pair13 14 void setY( int ); // set y in coordinate pair15 int getY() const; // return y from coordinate pair16 17 virtual void print() const; // output Point object18 19 private: 20 int x; // x part of coordinate pair21 int y; // y part of coordinate pair22 23 }; // end class Point24 25 #endif

Print declared virtual. It will be virtual in all derived classes.

circle.h (1 of 1)

1 // Fig. 10.9: circle.h2 // Circle class contains x-y coordinate pair and radius.3 #ifndef CIRCLE_H4 #define CIRCLE_H5 6 #include "point.h" // Point class definition7 8 class Circle : public Point {9 10 public:11 12 // default constructor13 Circle( int = 0, int = 0, double = 0.0 ); 14 15 void setRadius( double ); // set radius16 double getRadius() const; // return radius17 18 double getDiameter() const; // return diameter19 double getCircumference() const; // return circumference20 double getArea() const; // return area21 22 virtual void print() const; // output Circle object23 24 private: 25 double radius; // Circle's radius26 27 }; // end class Circle28 #endif

fig10_10.cpp(1 of 2)

1 // Fig. 10.10: fig10_10.cpp2 // Introducing polymorphism, virtual functions and dynamic3 // binding.4 #include <iostream>5 6 using std::cout;7 using std::endl;8 using std::fixed;9 10 #include <iomanip>11 12 using std::setprecision;13 14 #include "point.h" // Point class definition15 #include "circle.h" // Circle class definition16 17 int main()18 {19 Point point( 30, 50 );20 Point *pointPtr = 0;21 22 Circle circle( 120, 89, 2.7 );23 Circle *circlePtr = 0; 24 25 // set floating-point numeric formatting26 cout << fixed << setprecision( 2 );27

28 // output objects point and circle using static binding32 point.print(); // static binding33 cout << "\nCircle: ";34 circle.print(); // static binding35 36 // output objects point and circle using dynamic binding39 40 // aim base-class pointer at base-class object and print41 pointPtr = &point; 45 pointPtr->print();46 47 // aim derived-class pointer at derived-class48 // object and print 49 circlePtr = &circle; 53 circlePtr->print();54 55 // aim base-class pointer at derived-class object and print56 pointPtr = &circle; 60 pointPtr->print(); // polymorphism: invokes circle's print61 cout << endl;62 63 return 0;64 } // end main

At run time, the program determines that pointPtr is aiming at a Circle object, and calls Circle’s print function. This is an example of polymorphism.

Point: [30, 50]

Circle: Center = [120, 89]; Radius = 2.70

[30, 50]

Center = [120, 89]; Radius = 2.70

Review (Week10) _ Templates and File Processing

TemplatesFunction TemplatesClass Templates

File Processing Sequential-Access File

Random-Access Files

Function Templates

• Function-template definitions– Keyword template– List formal type parameters in angle brackets (< and >)

• Each parameter preceded by keyword class or typename– class and typename interchangeable

template< class T >

template< typename ElementType >

• Specify types of

– Arguments to function

– Return type of function

– Variables within function

61#include <iostream.h> //Tplate2.cpp#define max 5template <class Tpt>Tpt SumArray(const Tpt a[], int ){int i;Tpt sum;

sum = a[0];for( i=1; i < max; i++) sum = sum + a[i];

return sum;}int main(void){char screenoff;int a[max] = {1,2,3,4,5};float b[max]= {1.1, 2.2, 3.3, 4.4, 5.5}; cout << "Number sum : " << SumArray(a, max) << endl; cout << "Number sum : " << SumArray(b, max) << endl; cin >> screenoff;}

Class Templates

• Stack– LIFO (last-in-first-out) structure

• Class templates– Generic programming

– Describe notion of stack generically• Instantiate type-specific version

– Parameterized types• Require one or more type parameters

– Customize “generic class” template to form class-template specialization

Files and Streams

• To perform file processing– Include <iostream> and <fstream>– Class templates

• basic_ifstream (input)• basic_ofstream (output)• basic_fstream (I/O)

– typedefs for specializations that allow char I/O• ifstream (char input)• ofstream (char output)• fstream (char I/O)

// writing on a text file #include <iostream> #include <fstream> using namespace std;

int main () { // ofstream myfile ("example.txt");

ofstream myfile; myfile.open ("example.txt");

if (myfile.is_open()) {

myfile << "This is a line./n"; myfile << "This is another line./n";

myfile.close(); } else cout << "Unable to open file"; return 0;

[file example.txt] This is a line. This is another line.

1 // Fig. 14.4: fig14_04.cpp2 // Create a sequential file.3 #include <iostream>4 5 using std::cout;6 using std::cin;7 using std::ios;8 using std::cerr;9 using std::endl;10 11 #include <fstream>12 13 using std::ofstream;14 15 #include <cstdlib> // exit prototype16 17 int main()18 {19 // ofstream constructor opens file 20 ofstream outClientFile( "clients.dat", ios::out );21 22 // exit program if unable to create file23 if ( !outClientFile ) { // overloaded ! operator24 cerr << "File could not be opened" << endl;25 exit( 1 );26 27 } // end if

Notice the the header files required for file I/O.

ofstream object created and used to open file "clients.dat". If the file does not exist, it is created.

! operator used to test if the file opened properly.

28 29 cout << "Enter the account, name, and balance." << endl30 << "Enter end-of-file to end input.\n? ";31 32 int account;33 char name[ 30 ];34 double balance;35 36 // read account, name and balance from cin, then place in file37 while ( cin >> account >> name >> balance ) {38 outClientFile << account << ' ' << name << ' ' << balance39 << endl; 40 cout << "? ";41 42 } // end while43 44 return 0; // ofstream destructor closes file45 46 } // end main

cin is implicitly converted to a pointer. When EOF is encountered, it returns 0 and the loop stops.

Write data to file like a regular stream.

Enter the account, name, and balance.

Enter end-of-file to end input.

? 100 Jones 24.98

? 200 Doe 345.67

? 300 White 0.00

? 400 Stone -42.16

? 500 Rich 224.62

File closed when destructor called for object. Can be explicitly closed with close().

fig14_04.cppoutput (1 of 1)

1 Review (Week2) - Control Structures C++ has only seven control structures: –Sequence structure...

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