Chapter 14 More About Classes. CS 1410 - SJAllan Chapter 14 2 Instance and Static Members Instance variable: A member variable in a class Each object

Chapter 14

More About Classes

CS 1410 - SJAllan Chapter 14 2

Instance and Static Members

Instance variable: A member variable in a class Each object has its own copy

static variable: One variable shared among all objects of a class

static member function: Can be used to access static member variable Can be called before any objects are defined


Member (Instance)VariablesObject W1, W2


Member Variable is Static


Budget.h – Program #ifndef BUDGET_H#define BUDGET_H

class Budget{ private:

static double corpBudget;double divBudget;

public:Budget ( void ) { divBudget = 0; }void addBudget ( double b ) { divBudget += b; corpBudget += b; }double getDivBudget ( void ) { return divBudget; }double getCorpBudget ( void ) { return

corpBudget; }}; // Budget

double Budget::corpBudget = 0; // Static member#endif


testBudget.cpp – Program #include <iostream>#include <iomanip>#include "Budget.h" using namespace std;

int main ( void ){ int count;

const int NUMDIVISIONS = 4;Budget divisions[NUMDIVISIONS];for ( int count = 0; count < NUMDIVISIONS; count++ ){ double bud;

cout << "Enter the budget request for division ";

cout << (count + 1) << ": ";cin >> bud;divisions[count].addBudget(bud);

} // for


testBudget.cpp – Programcout << fixed << showpoint < setprecision(2);cout << "\nHere are the division budget requests:\n";for ( int count = 0; count < NUMDIVISIONS; count++ ){ cout << "\tDivision " << (count + 1) << "\t$ ";

cout << divisions[count].getDivBudget() << endl;} // forcout << "\tTotal Budget Requests:\t$ ";cout << divisions[0].getCorpBudget() << endl;

return 0;} // main


testBudget.cpp – Output

Enter the budget request for Division 1: 100000 [Enter]Enter the budget request for Division 2: 200000 [Enter]Enter the budget request for Division 3: 300000 [Enter]Enter the budget request for Division 4: 400000 [Enter]Here are the division budget requests:

Division 1 $ 100000.00Division 2 $ 200000.00Division 3 $ 300000.00Division 4 $ 400000.00Total Budget Requests: $ 1000000.00


Static Member Functions Declared with static before return type:

static int getVal ( ) { return valueCount; }

Can only access static member data Can be called independent of objects:

cout << "There are " <<IntVal::getVal( ) << " objects\n";


A New Budget.h – Program #ifndef BUDGET_H#define BUDGET_Hclass Budget{ private:

static double corpBudget;double divBudget;

public:Budget ( void ) { divBudget = 0; }void addBudget ( double b )

{ divBudget += b; corpBudget += b; }double getDivBudget ( void ) { return

divBudget; }double getCorpBudget ( void ) { return

corpBudget; }static void mainOffice ( double );

}; // Budget#endif


Budget.cpp – Program

#include "budget.h"

double Budget::corpBudget = 0;

void Budget::mainOffice ( double moffice ){ corpBudget += moffice;} // Budget::mainOffice


testBudget.cpp – Program #include <iostream>#include <iomanip>#include "Budget.h"using namespace std;

int main ( void ){ int count;

double mainOfficeRequestconst int NUMDIVISIONS = 4;cout << "Enter the main office's budget request: ";cin >> mainOfficeRequest;Budget::mainOffice( mainOfficeRequest );Budget divisions[NUMDIVISIONS];for ( count = 0; count < NUMDIVISIONS; count++ ){ double budgetAmount;

cout << "Enter the budget request for division ";cout << ( count + 1 ) << ": ";cin >> budgetAmount;divisions[count].addBudget( budgetAmount );

} // for


testBudget.cpp – Program

cout << fixed << showpoint << setprecision(2);cout << "\nHere are the division budget requests:\n";for (int count = 0; count < NUMDIVISIONS; count++){ cout << "\tDivision " << ( count + 1 ) << "\t$ ";

cout << divisions[count].getDivBudget() << endl;} // for

cout << "\tTotal Budget Requests (including main office):\t$ ";cout << divisions[0].getCorpBudget( ) << endl; return 0;

} // main


testBudget.cpp – Output

Enter the main office's budget request: 100000 [Enter]

Enter the budget request for Division 1: 100000 [Enter]




Here are the division budget requests:Division 1 $ 100000.00Division 2 $ 200000.00Division 3 $ 300000.00Division 3 $ 400000.00Total Requests (including main office): $ 1100000.00


Friends of Classes Friend

A function or class that is not a member of a class, but has access to private members of the class

A friend function can be a stand-alone function or a member function of another class

It is declared a friend of a class with friend keyword in the function prototype


Friend Function Declarations

Stand-alone function:friend void setAVal ( intVal &, int ); Declares setAVal function be a friend of this class

Member function of another class:friend void SomeClass::setNum( int num ); setNum function from Someclass class is a friend

of this class


Friend Classes As mentioned before, it is possible to make

an entire class a friend of another class. class FriendClass{

…}; // FriendClassclass NewClass{ public:

friend class FriendClass;// declares entire class (Friendclass) as a friend of

this class…

}; // NewClass


Memberwise Assignment The assignment operator (=) may be used to

assign one object to another, or to initialize one object with another object’s data

Thus v2 = v1;

means that each member of one object is copied to its counterpart in the other object

Use when class is defined:IntVal v3 = v2;


Copy Constructors A copy constructor is a special constructor,

called whenever a new object is created and initialized with another object’s data

Assume the class PersonInfo has a member variable as follows: name char *.

Consider the following declarations: PersonInfo person1( "Maria Jones-Tucker",

25 ); PersonInfo person2 = person1;


PersonInfo person1("Maria Jones-Tucker", 25);

Maria Jones-Tucker

Dynamically allocated memory

namepointer


PersonInfo person2 = person1;

Maria Jones-Tucker

Both objects’ name members point to the same section of memory

person1’snamepointer

person2’snamepointer

Dynamically allocated memory


Programmer Defined Copy Constructor Allows us to solve the problem with pointers

PersonInfo::PersonInfo( PersonInfo &obj ){ name = new char[strlen( obj.name ) + 1];

strcpy( name, obj.name );age = obj.age;

} // PersonInfo::PersonInfo Copy constructor takes a reference

parameter to an object of the class


Programmer Defined Copy Constructor Consider the following:

PersonInfo info1( "Ann", 5 );PersonInfo info2 = info1;

info2.setName( "Jane" );

name

info1

name

info2“Ann” “Jane”


Using const Parameters

Because copy constructors are required to use reference parameters, they have access to their argument’s data PersonInfo::PersonInfo( PersonInfo &obj )

They should not be allowed to change the parameters, therefore, it is a good idea to make the parameter const so it can’t be modifiedPersonInfo::PersonInfo( const PersonInfo

&obj )


The Default Copy Constructor If a class doesn’t have a copy constructor, C+

+ automatically creates a default copy constructor

The default copy constructor performs a memberwise assignment


Operator Overloading

C++ allows you to redefine how standard operators work when used with class objects


Overloading the = Operator This is done with a member function such as:

void operator = ( const PersonInfo &right ); This member function is called as follows:

person2 = person1; person2.operator = ( person1 ); Note that the parameter, right, is declared as a

reference, for efficiency purposes The reference prevents the compiler form making a

copy of the object being passed into the function Also note that the parameter is declared constant so the

function does not accidentally change the contents of the argument


Operator Overload – Program#include <iostream>#include <cstring>using namespace std;class PersonInfo{ private:

char *name; int age;

public: PersonInfo ( char *n, int a ) { name = new char[strlen(n) + 1];

strcpy(name, n); age = a; } PersonInfo ( const PersonInfo &obj ) // Copy constructor

{ name = new char[strlen(obj.name) + 1]; strcpy(name, obj.name); age = obj.age; }

~PersonInfo ( void ) { delete [] name; } char *getName ( void ) { return name; } int getAge ( void ) { return age; } void operator= ( const PersonInfo &right )

{ delete [] name; name = new char[strlen( right.name ) + 1];

strcpy(name, right.name); age = right.age; }}; // PersonInfo


Operator Overload – Program int main ( void ){ PersonInfo jim("Jim Young", 27), bob("Bob Faraday", 32), clone =

jim;cout << "The Jim Object contains: " << jim.getName();cout << ", " << jim.getAge() << endl;cout << "The Bob Object contains: " << bob.getName();cout << ", " << bob.getAge() << endl;cout << "The Clone Object contains: " << clone.getName();cout << ", " << clone.getAge() << endl;cout << "Now the clone will change to Bob and ";cout << "Bob will change to Jim.\n";clone = bob;bob = jim;cout << "The Jim Object contains: " << jim.getName();cout << ", " << jim.getAge() << endl;cout << "The Bob Object contains: " << bob.getName();cout << ", " << bob.getAge() << endl;cout << "The Clone Object contains: " << clone.getName();cout << ", " << clone.getAge() << endl;return 0;

} // main


Operator Overload – Output

The Jim Object contains: Jim Young, 27The Bob Object contains: Bob Faraday, 32The Clone Object contains: Jim Young, 27Now the clone will change to Bob and Bob will change to Jim.The Jim Object contains: Jim Young, 27The Bob Object contains: Jim Young, 27The Clone Object contains: Bob Faraday, 32


The = Operator’s Return Value If the operator= function returns a void, as in

the previous example, then multiple assignment statements won’t work

To enable a statement such asperson3 = person2 = person1;

you must have the following prototype:PersonInfo operator= (const PersonInfo &Right);


The this Pointer

this is a special built-in pointer that is available in any member function

this contains the address of the object that called the member function

The this pointer is passed as a hidden argument to all non-static member functions

Use of this pointer

This refers to the class itself.


You can use “this” to refer to class variables.Class MyInt {

private:

int a;

public:

void MyInt(int a) {

// The 'this' pointer is used to get access to class variable “a” rather than local variable “a”

this->a = a;

}

void doit(){

}

};


You can use “this” even when it is the not requiredClass MyInt {

private:

int a;

public:

void MyInt(int a) {

this->a = a;

doit(); // both of these calls to the same thing. “this” is understood

this->doit(); // both of these calls to the same thing. “this” is understood

}

void doit(){ cout << “just Called contructor”;}

}};


Sometimes you need a name for yourself. “this” is that nameClass MyInt {

private:

int a;

public:

void MyInt(int a) {

this->a = a;

}

MyInt* returnBigger(MyInt * other){

if (other->a > a) return other;

return this; // If I am the bigger, return me!

}

};


The this Pointer

PersonInfo person1, person2; cout << person1.getName( ) << endl;

What does the this pointer point to? cout << person2.getName( ) << endl;

What does the this pointer point to?



Using this – Program #include <iostream>#include <cstring>using namespace std;

class PersonInfo{ private:

char *name; int age;

public: PersonInfo ( char *n, int a )

{ name = new char[strlen( n )+ 1]; strcpy( name, n ); age = a; }


Using this – ProgramPersonInfo ( const PersonInfo &obj ) // Copy

constructor{ name = new char[strlen(obj.name)+ 1]; strcpy(name, obj.name); age = obj.age; }

~PersonInfo ( void ) { delete [] name; }char *getName ( void ) { return name; }int getAge ( void ) { return age; } const PersonInfo operator= ( const PersonInfo

&right ){ delete [] name; name = new char[strlen( right.name ) +

1]; strcpy( name, right.name ); age = right.age; return *this; }

}; // PersonInfo


Using this – Program

int main ( void ){ PersonInfo jim("Jim Young", 27), bob("Bob Faraday", 32), clone = jim;

cout << "The Jim Object contains: " << jim.getName();cout << ", " << jim.getAge() << endl;cout << "The Bob Object contains: " << bob.getName();cout << ", " << bob.getAge() << endl;cout << "The Clone Object contains: " << clone.getName();cout << ", " << clone.getAge() << endl;cout << "Now the clone and Bob will change to Jim.\n";clone = bob = jim;cout << "The Jim Object contains: " << jim.getName();cout << ", " << jim.getAge() << endl;cout << "The Bob Object contains: " << bob.getName();cout << ", " << bob.getAge() << endl;cout << "The Clone Object contains: " << clone.getName();cout << ", " << clone.getAge() << endl;return 0;

} // main


Using this – Output

The Jim Object contains: Jim Young, 27The Bob Object contains: Bob Faraday, 32The Clone Object contains: Jim Young, 27Now the clone and Bob will change to Jim.The Jim Object contains: Jim Young, 27The Bob Object contains: Jim Young, 27The Clone Object contains: Jim Young, 27


Issues of Operator Overloading You can change an operator’s entire

meaning when you overload it – don’t You cannot change the number of

operands taken by an operator For example, the = symbol must always be a

binary operator Likewise, ++ and -- must always be unary

operators The following operators cannot overloaded

?: . .* :: sizeof


Operators That can be Overloaded


feetinch.h – Program

#ifndef FEETINCHES_H#define FEETINCHES_H

class FeetInches{ private:

int feet;int inches;void simplify(void);

public:FeetInches( int f = 0, int i = 0 )

{ feet = f; inches = i; simplify(); }void setFeet( int f ) { feet = f; }


feetinch.h – Program

void setInches( int i ) { inches = i; simplify(); }int getFeet(void) { return feet; }int getInches(void) { return inches; }FeetInches operator + (const FeetInches &); FeetInches operator - (const FeetInches &); FeetInches operator ++ ( void ); // Prefix ++FeetInches operator ++ ( int ); // Postfix ++bool operator > ( const FeetInches & );bool operator < ( const FeetInches & );bool operator == ( const FeetInches & );friend ostream &operator << ( ostream & , const FeetInches & );friend istream &operator >> ( istream &, const FeetInches & );

}; // FeetInches#endif

FeetInches

Why didn’t we overload the assignment ( = ) operator?


simplify

3 feet 14 inches 4 feet 2 inches

5 feet -2 inches 4 feet 10 inches



feetinc.cpp – Program#include <cstdlib>#include "feetinch.h"

void FeetInches::simplify ( void ){ if ( inches >= 12 )

{ feet += (inches / 12); inches %= 12;

} // ifelse if ( inches < 0 ){ feet -= ( ( abs( inches ) / 12 ) + 1 );

inches = 12 - ( abs( inches ) % 12 );} // else

} // FeetInches::simplify


feetinc.cpp – ProgramFeetInches FeetInches::operator + ( const FeetInches

&right ){ FeetInches temp;

temp.inches = inches + right.inches;temp.feet = feet + right.feet;temp.simplify();return temp;

} // FeetInches::operator +

FeetInches FeetInches::operator - ( const FeetInches &right )

{ FeetInches temp;temp.inches = inches - right.inches;temp.feet = feet - right.feet;temp.simplify();return temp;

} // FeetInches::operator -


feetmain.cpp – Program#include <iostream>#include "feetinc2.h“using namespace std;int main ( void ){ FeetInches first, second, third;

int f, i;cout << "Enter a distance in feet and inches: ";cin >> f >> i;first.setData(f, i);cout << "Enter another distance in feet and inches: ";cin >> f >> i;second.setData(f, i);third = first + second;cout << "First + Second = ";cout << third.getFeet() << " feet, ";cout << third.getInches() << " inches.\n";third = first - second;cout << "First - Second = ";cout << third.getFeet() << " feet, ";cout << third.getInches() << " inches.\n";return 0;

} // main


feetmain.cpp – Output

Enter a distance in feet and inches: 6 5 [Enter]Enter another distance in feet and inches: 3 10 [Enter]First + Second = 10 feet, 3 inches.First - Second = 2 feet, 7 inches.


Note:

No return type is specified in the function header for the previous example Because it is a FeetInches-to-double conversion

function, it will always return a double


Overloading the Prefix ++ OperatorFeetInches FeetInches::operator ++ ( void ){ ++inches; simplify(); return *this;} // FeetInches::operator ++

What is Output?

int num 4;

cout << num++;

int num = 4;

Cout << ++num;


4

5


Overloading the Postfix ++ OperatorFeetInches FeetInches::operator ++ ( int ){ FeetInches temp( feet, inches ); inches++; simplify(); return temp;} // FeetInches::operator++


Overloading Relational Operatorsif (distance1 < distance2){ … code …} // if


Overloading Relational Operators

bool FeetInches:: operator > ( const FeetInches &right )

{ if (feet > right.feet) return true; else if (feet == right.feet && inches > right.inches) return true; else return false;} // FeetInches::operator >


Overloading the == Operatorbool FeetInches::operator == ( const FeetInches &right ){ if ( feet == right.feet && inches == right.inches ) return true; else

return false;} // FeetInches::operator ==


Overloading the << Operatorostream &operator << ( ostream &strm, FeetInches &obj ){ strm << obj.feet << " feet, " << obj.inches << " inches"; return strm;} // operator <<


Overloading the >> Operatoristream &operator >> ( istream &strm, FeetInches &obj ){ cout << "Feet: "; strm >> obj.feet; cout << "Inches: "; strm >> obj.inches;

return strm;} // operator >>


Overloading the [ ] Operator

In addition to the traditional operators, C++ allows you to change the way the [ ] (subscript) symbols work

Must consider constructor, destructor Overloaded [ ] returns a reference to the

object, and not the object itself


Intarry.h – Program #ifndef INTARRY_H#define INTARRY_Hclass IntArray{ private:

int *aptr;int arraySize;void subscriptError( );

public:IntArray ( int ); // constructorIntArray ( const IntArray & ); //copy constructor~IntArray ( void ); // Destructorint size ( void ) { return arraySize };int &operator [] ( const int & ); // overloaded [ ] operator

}; // IntArray#endif


Intarray.cpp – Program IntArray::IntArray ( int s ){ arraySize = s; aptr = new int [s]; for ( int count = 0; count < arraySize; count++ )

*( aptr + count ) = 0;} // IntArray::IntArray

IntArray::IntArray ( const IntArray &obj ){ arraySize = obj.arraySize; aptr = new int [arraySize]; assert( aptr ); for ( int count = 0; count < arraySize; count ++ ) *( aptr + count ) = *( obj.aptr + count );} // IntArray::IntArray


Intarray.cpp – ProgramIntArray::~IntArray ( void ){ if ( arraySize > 0 )

delete [] aptr;} // IntArray::~IntArray

int &IntArray::operator [] ( const int &sub ){ if ( sub < 0 || sub > arraySize )

subscriptError(); return aptr[sub];} // IntArray::operator []


Intarray.cpp – Program

void IntArray::subscriptError( void ){ cout << "ERROR: Subscript out of range.\n";

exit( 0 );} // IntArray::subscriptError


Object Conversion

Special operator functions may be written to convert a class object to any other typeFeetInches::operator double ( void ){ double temp = feet;

temp += ( inches / 12.0 );return temp;

} // FeetInches::operator double


Creating a String Class

This example shows the use of a C++ class to create a string data type


The MyString Class

Memory is dynamically allocated for any string stored in a MyString object

Strings may be assigned to a MyString object with the = operator

One string may be concatenated to another with the += operator

Strings may be tested for equality with the == operator


MyString.h – Program #ifndef MYSTRING_H#define MYSTRING_H#include <iostream>using namespace std;class MyString; // Forward declarationsostream &operator << ( ostream &, const MyString & );istream &operator >> ( istream &, MyString & );class MyString{ private:

char *str;int len;

public:MyString( void ) { str = NULL; len = 0; }MyString( char * ){ len = strlen( sptr );

str = new char[len + 1 ];strcpy( str, sptr; }


MyString.h – ProgramMyString( MyString &right) // Copy constructor{ str = new char[ right.length() + 1];

strcpy( str, right.getValue() );len = right.length();

}~MyString( void ) { if ( len != 0 ) delete [] str; }int length ( void ) { return len; }char *getValue ( void ) { return str; };


MyString.h – Program// Overloaded operatorsMyString operator += ( MyString & );char *operator += ( const char * );MyString operator = ( MyString & );char *operator = ( const char * );int operator == ( MyString & );int operator == ( const char * );int operator != ( MyString & );int operator != ( const char * );bool operator > ( MyString & );bool operator > ( const char * );bool operator < ( const char * ); bool operator < ( MyString & );bool operator >= ( MyString & );bool operator >= ( const char * );bool operator <= ( const char * ); bool operator <= ( MyString & );friend ostream &operator << ( ostream &, MyString & );friend istream &operator >> ( istream &, MyString & );

}; // MyString#endif


MyString.cpp – Program#include <cstring>#include "MyString.h"using namespace std;

MyString MyString::operator = ( MyString &right ){ if ( len != 0 ) delete [];

str = new char[right.length() + 1];strcpy(str, right.getValue());len = right.length();return *this;

} // MyString::operator =

MyString MyString::operator = ( const char *right ){ if ( len != 0 ) delete [] str;

len = strlen( right );str = new char[len + 1];strcpy( str, right );return *this;

} // MyString::operator =


MyString.cpp – Program

MyString MyString::operator += ( MyString &right ){ char *temp = str;

str = new char[strlen(str) + right.length() + 1];strcpy( str, temp );strcat( str, right.getvalue() );if ( len != 0 )

delete [] temp;len = strlen(str);return *this;

} // MyString::operator +=


MyString.cpp – Program (cont)char *MyString::operator += ( const char *right ){ char *temp = str;

str = new char[strlen(str) + strlen(right) + 1];strcpy( str, temp );strcat( str, right );if ( len != 0 )

delete [] temp;return str;

} // MyString::operator +=

int MyString::operator == ( MyString &right ){ return !strcmp( str, right.getValue() ) ;} // MyString::operator ==


MyString.cpp – Programint MyString::operator == ( const char *right ){ return !strcmp( str, right );} // MyString::operator ==

int MyString::operator != ( MyString &right ){ return strcmp( str, right.getValue() );} // MyString::operator !=

int MyString::operator != ( const char *right ){ return strcmp( str, right );} // MyString::operator !=

bool MyString::operator >(MyString &right){ if ( strcmp( str, right.getValue() ) > 0 )

return true;else

return false;} // MyString::operator >


MyString.cpp – Programbool MyString::operator > ( const char *right ){ if ( strcmp( str, right ) > 0 )

return true;else

return false;} // MyString::operator >

bool MyString::operator < ( MyString &right ){ if ( strcmp( str, right.getValue() ) < 0 )

return true;else

return false;} // MyString::operator <

bool MyString::operator < ( const char *right ){ if ( strcmp( str, right ) < 0 )

return true;else

return false;} // MyString::operator <


MyString.cpp – Programbool MyString::operator >= ( MyString &right ){ if ( strcmp( str, right.getValue() ) >= 0 )

return true;else

return false;} // MyString::operator >=

bool MyString::operator >= ( const char *right ){ if ( strcmp( str, right ) >= 0 )

return true;else

return false;} // MyString::operator >=

bool MyString::operator <= ( MyString &right ){ if ( strcmp( str, right.getValue() ) <= 0 )

return true;else

return fals;} // MyString::operator <=


MyString.cpp – Programbool MyString::operator <= (const char *right ){ if ( strcmp( str, right ) <= 0 )

return true;else

return false;} // MyString::operator <=

ostream &operator << ( ostream &strm, const MyString &obj ){ strm << obj.str;

return strm;} // operator <<

istream &operator >>( istream &strm, MyString &obj ){ strm.getline(obj.str, obj.len);

strm.ignore();return strm;

} // operator >>


MystrMain.cpp – Program#include <iostream>#include "Mystring.h"using namespace std;

int main ( void ){ MyString object1("This"), object2("is");

MyString object3("a test.");MyString object4 = object1; MyString object5("is only a test.");char string1[] = "a test.";cout << "Object1: " << object1 << endl;cout << "Object2: " << object2 << endl;cout << "Object3: " << object3 << endl;cout << "Object4: " << object4 << endl;cout << "Object5: " << object5 << endl;


MystrMain.cpp – Program

cout << "String1: " << string1 << endl;object1 += " ";object1 += object2;object1 += " ";object1 += object3;object1 += " ";object1 += object4;object1 += " ";object1 += object5;cout << "Object1: " << object1 << endl;

return 0;} // main


MystrMain.cpp – Output

Object1: This Object2: isObject3: a test.Object4: This Object5: is only a test.String1: a test.Object1: This is a test. This is only a test.


MystrMain.cpp – Program #include <iostream>#include “Mystring.h“using namespace std;

int main ( void ){ MyString name1("Billy"), name2("Sue");

MyString name3("joe");MyString string1("ABC"), string2("DEF");

cout << “name1: " << name1.getValue() << endl;cout << “name2: " << name2.getValue() << endl;cout << “name3: " << name3.getValue() << endl;cout << “string1: " << string1.getValue() << endl;cout << “string2: " << string2.getValue() << endl;


MystrMain.cpp – Programif ( name1 == name2 )

cout << “name1 is equal to Name2.\n";else

cout << “name1 is not equal to Name2.\n";if ( name3 == "joe" )

cout << “name3 is equal to joe.\n";else

cout << “name3 is not equal to joe.\n";if ( string1 > string2 )

cout << “string1 is greater than String2.\n";else

cout << “string1 is not greater than String2.\n";if ( string1 < string2 )

cout << “string1 is less than String2.\n";else


MystrMain.cpp – Programcout << "string1 is not less than String2.\n";

if ( string1 >= string2 )cout << "string1 is greater than or equal to " << "string2.\n";

elsecout << "string1 is not greater than or equal to " << "string2.\n";

if ( string1 >= "ABC" )cout << "string1 is greater than or equal to " << "ABC.\n";

elsecout << "string1 is not greater than or equal to " << "ABC.\n";

if ( string1 <= string2 )cout << "string1 is less than or equal to " << "string2.\n";


MystrMain.cpp – Program

elsecout << "string1 is not less than or equal to " << "string2.\n";

if (string2 <= "DEF")cout << "string2 is less than or equal to " << "DEF.\n";

elsecout << "string2 is not less than or equal to " << "DEF.\n";

return 0;} // main


MystrMain.cpp – Output name1: Billyname2: Suename3: joestring1: ABCstring2: DEFname1 is not equal to Name2.name3 is equal to joe.string1 is not greater than String2.string1 is less than String2.string1 is not greater than or equal to String2.string1 is greater than or equal to ABC.string1 is less than or equal to String2.string2 is less than or equal to DEF.


Object Composition

Object composition occurs when a class contains an instance of another class

Creates a “has a” relationship between classes

The notation for structures within structures is used with object composition

Documents

Chapter 14 More About Classes. CS 1410 - SJAllan Chapter 14 2 Instance and Static Members Instance variable: A member variable in a class Each object