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[НЕСОРТИРОВАННОЕ]

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Answers to Questions and Exercises

3. base

4. virtual void dang(int); or void virtual dang(int);

5.late binding or dynamic binding

6.derived

7. virtual void aragorn()=0; or void virtual aragorn()=0;

8.a, c

9.dong* parr[10];

10.c

11.true

12.c, d

13.friend void harry(george);

14.a, c, d

15.friend class harry; or friend harry;

16.c

17.It performs a member-by-member copy.

18.zeta& operator = (zeta&);

19.a, b, d

20.false; the compiler provides a default copy constructor

21.a, d

22.Bertha(Bertha&);

23.true, if there was a reason to do so

24.a, c

25.true; trouble occurs if it’s returned by reference

26.They operate identically.

27.a, b

28.the object of which the function using it is a member

29.no; since this is a pointer, use this->da=37;

30.return *this;

31.c

32.links

33.true

34.a, b, c

955

Q E UESTIONS ANSWERS XERCISES AND TO

Appendix G

956

Solutions to Exercises

//ex11_1.cpp

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

#include <string> using namespace std;

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

class publication

{

private:

string title; float price;

public:

virtual void getdata()

{

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

}

virtual void putdata()

{

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

}

};

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

class book : public publication

{

private:

int pages; public:

void getdata()

{

publication::getdata();

cout << “Enter number of pages: “; cin >> pages;

}

void putdata()

{

publication::putdata();

cout << “\nPages: “ << pages;

}

};

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

class tape : public publication

{

Answers to Questions and Exercises

private:

float time; public:

void getdata()

{

publication::getdata();

cout << “Enter playing time: “; cin >> time;

}

void putdata()

{

publication::putdata();

cout << “\nPlaying time: “ << time;

}

};

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

int main()
{
publication* pubarr[100];	//array of ptrs		to pubs
int n = 0;	//number	of pubs in array
char choice;	//user’s	choice

do {

cout << “\nEnter data for book or tape (b/t)? “;

cin >> choice;
if( choice==’b’ )	//make book object
pubarr[n] = new book;	//	put in array
else	//make tape object
pubarr[n] = new tape;	//	put in array
pubarr[n++]->getdata();	//get data for object
cout << “ Enter another (y/n)? “;		//another pub?
cin >> choice;
}
while( choice ==’y’);	//cycle until not ‘y’
for(int j=0; j<n; j++)	//cycle thru all pubs
pubarr[j]->putdata();	//print data for pub
cout << endl;
return 0;
}

//ex11_2.cpp

//friend square() function for Distance #include <iostream>

using namespace std;

957

Q E UESTIONS ANSWERS XERCISES AND TO

Appendix G

958

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

class Distance	//English Distance class
{
private:
int feet;
float inches;
public:
Distance()	//constructor (no args)
{ feet = 0; inches = 0.0; }
Distance(float fltfeet)	//constructor (one arg)
{	//feet is integer part
feet = static_cast<int>(fltfeet);
inches = 12*(fltfeet-feet); //inches is what’s left
}	//constructor (two args)

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

	{ }
void showdist()		//display distance
	{ cout << feet << “\’-” << inches << ‘\”’; }
friend Distance operator * (Distance, Distance); //friend
};
//--------------------------------------------------------------
		//multiply d1 by d2
Distance	operator * (Distance d1, Distance d2)
{
float fltfeet1 = d1.feet + d1.inches/12;			//convert to float
float fltfeet2 = d2.feet + d2.inches/12;
float multfeet = fltfeet1 * fltfeet2;			//find the product
return Distance(multfeet);		//return temp Distance
}

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

int main()
{
Distance dist1(3, 6.0);		//make some distances
Distance dist2(2, 3.0);
Distance dist3;
dist3 =	dist1 * dist2;	//multiplication
dist3 =	10.0 * dist3;	//mult and conversion
		//display all distances
cout <<	“\ndist1 = “; dist1.showdist();
cout <<	“\ndist2 = “; dist2.showdist();
cout <<	“\ndist3 = “; dist3.showdist();
cout <<	endl;

return 0;

}

Answers to Questions and Exercises

//ex11_3.cpp

//creates array class

//overloads assignment operator and copy constructor #include <iostream>

using namespace std;

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

class Array

{

private:
int* ptr;	//pointer to “array” contents
int size;	//size of array
public:
Array() : ptr(0), size(0)	//no-argument constructor
{ }
Array(int s) : size(s)	//one-argument constructor
{ ptr = new int[s]; }
Array(Array&);	//copy constructor
~Array()	//destructor
{ delete[] ptr; }
int& operator [] (int j)	//overloaded subscript op
{ return *(ptr+j); }
Array& operator = (Array&);		//overloaded = operator
};
//--------------------------------------------------------------
Array::Array(Array& a)	//copy constructor
{
size = a.size;	//new one is same size
ptr = new int[size];	//get space for contents
for(int j=0; j<size; j++)	//copy contents to new one
(ptr+j) = (a.ptr+j);
}
//--------------------------------------------------------------
Array& Array::operator = (Array& a)		//overloaded = operator
{
delete[] ptr;	//delete old contents (if any)
size = a.size;	//make this object same size
ptr = new int[a.size];	//get space for new contents
for(int j=0; j<a.size; j++)	//copy contents to this object
(ptr+j) = (a.ptr+j);
return *this;	//return this object
}

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

int main()
{
const int ASIZE = 10;	//size of array

959

Q E UESTIONS ANSWERS XERCISES AND TO

960	Appendix G

Array arr1(ASIZE);		//make an array
for(int	j=0; j<ASIZE; j++) //fill it with squares
arr1[j] = j*j;
Array arr2(arr1);		//use the copy constructor
cout <<	“\narr2: “;
for(j=0; j<ASIZE; j++)		//check that it worked
cout	<< arr2[j] << “	“;
Array arr3, arr4;		//make two empty Array objects
arr4 = arr3 = arr1;		//use the assignment operator
cout <<	“\narr3: “;
for(j=0; j<ASIZE; j++)		//check that it worked on arr3
cout	<< arr3[j] << “	“;
cout <<	“\narr4: “;
for(j=0; j<ASIZE; j++)		//check that it worked on arr4
cout	<< arr4[j] << “	“;
cout <<	endl;

return 0;

}

Chapter 12

Answers to Questions

1.b, c

2.ios

3.ifstream, ofstream, and fstream

4.ofstream salefile (“SALES.JUN”);

5.true

6.if(foobar)

7.d

8.fileOut.put(ch); (where ch is the character)

9.c

10.ifile.read( (char*)buff, sizeof(buff) );

11.a, b, d

12.the byte location at which the next read or write operation will take place

13.false; file pointer can be a synonym for current position

14.f1.seekg(-13, ios::cur);

Answers to Questions and Exercises

961

15.b

16.b, c

17.skipws causes whitespace characters to be ignored on input so that cin will not assume the input has terminated.

18.int main(int argc, char *argv[] )

19.PRN, LPT1

20.istream& operator >> (istream&, Sample& )

Solutions to Exercises

//	ex12_1.cpp
//	write	array
#include		<iostream>
#include		<fstream>	// for file streams

using namespace std;

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

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

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

{}

void	getdist()	// get length from user
{
cout << “\n		Enter feet: “;	cin >> feet;
cout << “		Enter inches: “;	cin >> inches;
}
void	showdist()	// display distance

{ cout << feet << “\’-” << inches << ‘\”’; }

};

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

int main()
{
char ch;
Distance dist;	//	create a Distance object
fstream file;	//	create input/output file
	// open it for append
file.open(“DIST.DAT”, ios::binary		\| ios::app \|
	ios::out \| ios::in );

Q E UESTIONS ANSWERS XERCISES AND TO

962	Appendix G

do		// data from user to file
	{
	cout << “\nDistance”;
	dist.getdist();	// get a distance
		// write to file
	file.write( (char*)&dist, sizeof(dist) );
	cout << “Enter another distance (y/n)? “;
	cin >> ch;
	}
while(ch==’y’);		// quit on ‘n’
file.seekg(0);		// reset to start of file
		// read first distance
file.read( (char*)&dist, sizeof(dist) );
int count = 0;
while( !file.eof() )		// quit on EOF
	{
	cout << “\nDistance “ << ++count << “: “;		// display dist
	dist.showdist();
	file.read( (char*)&dist, sizeof(dist) );		// read another
	}		// distance
cout << endl;
return 0;
}
2.
// ex12_2.cpp
// imitates COPY command
#include <fstream>		//for file functions
#include <iostream>
using	namespace std;
#include <process.h>		//for exit()
int main(int argc, char* argv[] )
{
if( argc != 3 )
	{ cerr << “\nFormat: ocopy srcfile destfile”; exit(-1); }
char ch;		//character to read
ifstream infile;		//create file for input
infile.open( argv[1] );		//open file
if( !infile )		//check for errors
	{ cerr << “\nCan’t open “ << argv[1]; exit(-1); }
ofstream outfile;		//create file for output
outfile.open( argv[2] );		//open file

Answers to Questions and Exercises

963

if( !outfile )	//check for errors
{ cerr << “\nCan’t open “ << argv[2]; exit(-1); }
while( infile )	//until EOF
{
infile.get(ch);	//read a character
outfile.put(ch);	//write the character
}
return 0;
}

//ex12_3.cpp

//displays size of file

#include <fstream>		//for	file functions
#include	<iostream>
using namespace std;
#include	<process.h>	//for	exit()

int main(int argc, char* argv[] )

{

if( argc != 2 )

{	cerr << “\nFormat: filename\n”; exit(-1); }
ifstream infile;		//create file for input
infile.open( argv[1] );		//open file
if( !infile )		//check for errors
{	cerr << “\nCan’t open “ << argv[1]; exit(-1); }
infile.seekg(0, ios::end);		//go to end of file
		// report byte number
cout	<< “Size of “ << argv[1] << “ is “ << infile.tellg();
cout	<< endl;
return 0;
}

Chapter 13

Answers to Questions

1.a, b, c, d

2.#include directive

3.the compiler to compile the .CPP file and the linker to link the resulting .OBJ files

4.a, b

5.class library

Q E UESTIONS ANSWERS XERCISES AND TO

Appendix G

964

6.true

7.c, d

8.true

9.false

10.a, c, d

11.linking

12.false

13.d

14.scope

15.object

16.declared, file B

17.true

18.b

19.false

20.d

21.b

22.namespace

22. b, d

Chapter 14

Answers to Questions

1.b and c

2.class

3.false; different functions are created at compile time

template<class T> T times2(T arg)

{

return arg*2;

}

5.b

6.true

7.instantiating

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