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[НЕСОРТИРОВАННОЕ]

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lafore_robert_objectoriented_programming_in_c

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Answers to Questions and Exercises

935

public:
void getdata()	//get data from user
{
cout << “\nEnter name: “; cin >> name;
cout << “Enter number: “; cin >> number;
}
void putdata()	//display data
{
cout << “\n	Name: “ << name;
cout << “\n	Number: “ << number;
}
};

////////////////////////////////////////////////////////////////

int main()
{
employee emparr[100];	//an array of employees
int n = 0;	//how many employees
char ch;	//user response
do {	//get data from user
cout << “\nEnter data for employee number “ << n+1;
emparr[n++].getdata();
cout << “Enter another (y/n)? “; cin >> ch;
} while( ch != ‘n’ );
for(int j=0; j<n; j++)	//display data in array
{

cout << “\nEmployee number “ << j+1; emparr[j].putdata();

}

cout << endl; return 0;

}

//ex7_3.cpp

//averages an array of Distance objects input by user #include <iostream>

using namespace std;

////////////////////////////////////////////////////////////////

class Distance	// English Distance class
{
private:
int feet;
float inches;

Q E UESTIONS ANSWERS XERCISES AND TO

936	Appendix G

public:
Distance()		//constructor (no args)
{ feet = 0; inches = 0; }
Distance(int ft, float in)		//constructor (two args)
{ feet = ft; inches = in; }
void	getdist()	//get length from user
{
cout << “\nEnter feet: “;		cin >> feet;
cout << “Enter inches: “;		cin >> inches;
}
void	showdist()	//display distance
{	cout << feet << “\’-” << inches << ‘\”’; }
void	add_dist( Distance, Distance );		//declarations
void	div_dist( Distance, int );
};

//--------------------------------------------------------------

//add Distances d2 and d3 void Distance::add_dist(Distance d2, Distance d3)

{
inches = d2.inches + d3.inches;	//add the inches
feet = 0;	//(for possible carry)
if(inches >= 12.0)	//if total exceeds 12.0,
{	//then decrease inches
inches -= 12.0;	//by 12.0 and
feet++;	//increase feet
}	//by 1
feet += d2.feet + d3.feet;	//add the feet
}

//--------------------------------------------------------------

//divide Distance by int
void Distance::div_dist(Distance d2, int divisor)
{
float fltfeet = d2.feet + d2.inches/12.0;	//convert to	float
fltfeet /= divisor;	//do division
feet = int(fltfeet);	//get feet part
inches = (fltfeet-feet) * 12.0;	//get inches	part
}

////////////////////////////////////////////////////////////////

int main()
{
Distance distarr[100];	//array of	100 Distances
Distance total(0, 0.0), average; //other		Distances
int count = 0;	//counts Distances input

		Answers to Questions and Exercises	937
char ch;	//user response character		937


do {
cout << “\nEnter a Distance”;		//get Distances
distarr[count++].getdist();		//from user, put
cout << “\nDo another (y/n)? “;		//in array
cin >> ch;
}while( ch != ‘n’ );
for(int j=0; j<count; j++)		//add all Distances
total.add_dist( total, distarr[j] );		//to total
average.div_dist( total, count );		//divide by number
cout << “\nThe average is: “;		//display average
average.showdist();
cout << endl;
return 0;
}

Chapter 8

Answers to Questions

1.a, c

2.x3.subtract(x2, x1);

3.x3 = x2 - x1;

4.true

5.void operator -- () { count--; }

6.none

7.b, d

void Distance::operator ++ ()

{

++feet;

}

Distance Distance::operator ++ ()

{

int f = ++feet; float i = inches;

return Distance(f, i);

}

Q E UESTIONS ANSWERS XERCISES AND TO

Appendix G

938

10.It increments the variable prior to use, the same as a non-overloaded ++operator.

11.c, e, b, a, d

12.true

13.b, c

14.

String String::operator ++ ()

{

int len = strlen(str); for(int j=0; j<len; j++)

str[j] = toupper( str[j] ) return String(str);

}

15.d

16.false if there is a conversion routine; true otherwise

17.b

18.true

19.constructor

20.true, but it will be hard for humans to understand

21.d

22.attributes, operations

23.false

24.a

Solutions to Exercises

//ex8_1.cpp

//overloaded ‘-’ operator subtracts two Distances #include <iostream>

using namespace std;

////////////////////////////////////////////////////////////////

class Distance	//English Distance class
{
private:
int feet;
float inches;
public:	//constructor (no args)
Distance() : feet(0), inches(0.0)
{ }	//constructor (two args)

Answers to Questions and Exercises

939

Distance(int ft, float in) : feet(ft), inches(in)

	{	}
void		getdist()	//get length from user
	{
	cout << “\nEnter feet: “;		cin >> feet;
	cout << “Enter inches: “;		cin >> inches;
	}
void		showdist()	//display distance
	{	cout << feet << “\’-” << inches << ‘\”’; }
Distance operator + ( Distance );				//add two distances
Distance operator - ( Distance );				//subtract two distances
};
//--------------------------------------------------------------
			//add d2 to this distance
Distance	Distance::operator + (Distance d2)				//return the sum
{
int f	= feet + d2.feet;		//add the feet
float	i = inches + d2.inches;		//add the inches
if(i >= 12.0)			//if total exceeds 12.0,
{			//then decrease inches
i -= 12.0;			//by 12.0 and
f++;			//increase feet by 1
}			//return a temporary Distance
return Distance(f,i);			//initialized to sum
}
//--------------------------------------------------------------
			//subtract d2 from this dist
Distance	Distance::operator - (Distance d2)				//return the diff
{
int f	= feet - d2.feet;		//subtract the feet
float	i = inches - d2.inches;		//subtract the inches
if(i < 0)			//if inches less than 0,
{			//then increase inches
i += 12.0;			//by 12.0 and
f--	;		//decrease feet by 1
}			//return a temporary Distance
return Distance(f,i);			//initialized to difference
}

////////////////////////////////////////////////////////////////

int main()
{
Distance dist1, dist3;	//define distances
dist1.getdist();	//get dist1 from user

Q E UESTIONS ANSWERS XERCISES AND TO

Distance dist2(3, 6.25);

//define, initialize dist2

Appendix G

940

dist3 = dist1 - dist2;

//subtract

//display all lengths cout << “\ndist1 = “; dist1.showdist();

cout << “\ndist2 = “; dist2.showdist(); cout << “\ndist3 = “; dist3.showdist(); cout << endl;

return 0;

}

//ex8_2.cpp

//overloaded ‘+=’ operator concatenates strings #include <iostream>

#include	<cstring>	//for strcpy(), strlen()
using namespace std;
#include	<process.h>	//for exit()

////////////////////////////////////////////////////////////////

class String		//user-defined string type
{
private:
enum	{ SZ = 80 };		//size of String objects
char	str[SZ];		//holds a C-string
public:
String()			//no-arg constructor
{ strcpy(str, “”); }
String( char s[] )			//1-arg constructor
{ strcpy(str, s); }
void display()			//display the String
{ cout << str; }
String operator += (String ss) //add a String to this one
{			//result stays in this one
if( strlen(str) + strlen(ss.str) >= SZ )
	{ cout << “\nString overflow”; exit(1); }
strcat(str, ss.str);			//add the argument string
return String(str);			//return temp String
}
};

////////////////////////////////////////////////////////////////

int main()
{
String s1	= “Merry Christmas! “;	//uses 1-arg		ctor
String s2	= “Happy new year!”;	//uses	1-arg	ctor
String s3;		//uses	no-arg ctor

				Answers to Questions and Exercises

s3 =	s1	+= s2;	//add s2 to s1, assign to s3
cout	<< “\ns1=”; s1.display();			//display s1
cout	<< “\ns2=”; s2.display();			//display s2
cout	<< “\ns3=”; s3.display();			//display s3
cout	<< endl;

return 0;

}

//ex8_3.cpp

//overloaded ‘+’ operator adds two times #include <iostream>

using namespace std;

////////////////////////////////////////////////////////////////

class time

{

private:

int hrs, mins, secs; public:

time() : hrs(0), mins(0), secs(0) //no-arg constructor

{ } //3-arg constructor time(int h, int m, int s) : hrs(h), mins(m), secs(s)

{}

void	display()	//format 11:59:59
{	cout << hrs << “:” << mins << “:”		<< secs; }
time	operator + (time t2)	//add two times
{
int s = secs + t2.secs;		//add seconds
int m = mins + t2.mins;		//add minutes
int h = hrs + t2.hrs;		//add hours
if( s > 59 )		//if	secs overflow,
	{ s -= 60; m++; }	//	carry a minute
if( m > 59 )		//if	mins overflow,
	{ m -= 60; h++; }	//	carry an hour
return time(h, m, s);		//return temp value
}

};

////////////////////////////////////////////////////////////////

int main()
{
time time1(5, 59, 59);	//create and initialze
time time2(4, 30, 30);	// two times
time time3;	//create another time

941

Q E UESTIONS ANSWERS XERCISES AND TO

Appendix G

942

time3 =		time1	+ time2;	//add two times
cout	<<	“\ntime3 = “; time3.display(); //display result
cout	<<	endl;

return 0;

}

//ex8_4.cpp

//overloaded arithmetic operators work with type Int #include <iostream>

using namespace std;

#include <process.h> //for exit()

////////////////////////////////////////////////////////////////

class Int
{
private:
int i;
public:
Int() : i(0)		//no-arg constructor
{	}
Int(int ii) : i(ii)		//1-arg constructor
{	}	//	(int to Int)
void	putInt()	//display Int
{	cout << i; }
void	getInt()	//read Int from kbd
{ cin >> i; }
operator int()		//conversion operator
{ return i; }		//	(Int to int)
Int operator + (Int i2)		//addition
{ return checkit( long double(i)+long double(i2) ); }
Int operator - (Int i2)		//subtraction
{ return checkit( long double(i)-long double(i2) ); }
Int operator * (Int i2)		//multiplication
{ return checkit( long double(i)*long double(i2) ); }
Int operator / (Int i2)		//division
{ return checkit( long double(i)/long double(i2) ); }
Int checkit(long double answer)			//check results
{

if( answer > 2147483647.0L || answer < -2147483647.0L ) { cout << “\nOverflow Error\n”; exit(1); }

return Int( int(answer) );

}

};

////////////////////////////////////////////////////////////////

int main()

{

Answers to Questions and Exercises

943

Int alpha = 20;

Int beta = 7;

Int delta, gamma;

gamma =	alpha + beta;	//27
cout <<	“\ngamma=”; gamma.putInt();
gamma =	alpha - beta;	//13
cout <<	“\ngamma=”; gamma.putInt();
gamma =	alpha * beta;	//140
cout <<	“\ngamma=”; gamma.putInt();
gamma =	alpha / beta;	//2
cout <<	“\ngamma=”; gamma.putInt();
delta =	2147483647;
gamma =	delta + alpha;	//overflow error
delta =	-2147483647;
gamma =	delta - alpha;	//overflow error

cout << endl; return 0;

}

Chapter 9

Answers to Questions

1.a, c

2.derived

3.b, c, d

4.class Bosworth : public Alphonso

5.false

6.protected

7.yes (assuming basefunc is not private)

8.BosworthObj.alfunc();

9.true

10.the one in the derived class

11.Bosworth() : Alphonso() { }

12.c, d

13.true

14.Derv(int arg) : Base(arg)

Q E UESTIONS ANSWERS XERCISES AND TO

Appendix G

944

15.a

16.true

17.c

18.class Tire : public Wheel, public Rubber

19.Base::func();

20.false

21.generalization

22.d

23.false

24.stronger, aggregation

Solutions to Exercises

//ex9_1.cpp

//publication class and derived classes #include <iostream>

#include <string> using namespace std;

////////////////////////////////////////////////////////////////

class publication	// base class
{
private:
string title;
float price;
public:
void getdata()
{

cout << “\nEnter title: “; cin >> title; cout << “Enter price: “; cin >> price;

}

void putdata() const

{

cout << “\nTitle: “ << title; cout << “\nPrice: “ << price;

}

};

////////////////////////////////////////////////////////////////

class book : private publication	// derived class
{
private:
int pages;

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