Chapter 8

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Chapter 8

Operator Overloading, Friends, and References

This activity contains 10 questions.

What is the output of the following program?


class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	void SetNumber(int n);
};

Number::Number() {}

Number::Number(int n)
{
	m_num = n;
}

int Number::GetNumber()
{
	return m_num;
}

void Number::SetNumber(int n)
{
	m_num = n;
}

int main()
{
	Number num1(5), num2;

	num2 = num1;
	num1.SetNumber(10);
	cout << num1.GetNumber() << " " 
	   << num2.GetNumber() << endl;
	return 0;
}

10 510 10An error message will result because we have not overloaded the = operator.5 5

Which of the following is not a valid reason to use const in the declaration below?
const Money operator +(const Money &amount1, const Money &amount2);

When we want to improve the efficiency of the program by passing the arguments as call by reference.When we would like the compiler to flag as errors subtle bugs that may result when class objects are changed.When we want to ensure that the programmer cannot change the objects within the function definition.When we want to be able to directly modify the class that is returned.

What is the output of the following program?


class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	void SetNumber(int n);
};

Number::Number()
{
}

Number::Number(int n)
{
	m_num = n;
}

int Number::GetNumber()
{
	return m_num;
}

void Number::SetNumber(int n)
{
	m_num = n;
}

bool operator ==(Number& num1, Number& num2);

bool operator ==(Number& num1, Number& num2)
{
	int f;
	f = abs(num1.GetNumber() --
	   num2.GetNumber());
	return (f==1);
}

int main()
{
 Number num1(5), num2(6), num3(5);

 if (num1 == num2) {
 cout << "Num1 and Num2 are the same" << endl;
 }
 if (num1 == num3) {
  cout << "Num1 and Num3 are the same" << endl;
 }
 return 0;
}

An error message. We are not allowed to compare class objects using ==.NothingNum1 and Num2 are the sameNum1 and Num3 are the same

Which of the following prototypes is invalid?

int operator %(Number x, Number y);int operator %(Number x, int y);int operator %(const Number &x, const Number &y);int operator %(int x, int y);

The following code is intended to print out "6" but instead it prints out "5". How could we correct the error?


class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	void SetNumber(int n);
};

Number::Number()
{
}

Number::Number(int n)
{
	m_num = n;
}

int Number::GetNumber()
{
	return m_num;
}

void Number::SetNumber(int n)
{
	m_num = n;
}

Number operator ++(Number &num)
{	
	return Number(num.GetNumber()+1);
}

int main()
{
	Number num1(5);
	++num1;
	cout << num1.GetNumber() << endl;
	return 0;
}

Number operator ++(Number &num)
{	
	int temp = num.GetNumber()+1;
	num.SetNumber(temp);
	return Number(temp);
}

int operator ++(Number &num)
{	
    return Number(num.GetNumber()+1);
}

Number operator ++(Number &num)
{	
	int temp = num.GetNumber()+1;
	return Number(temp);
}

num1++; instead of ++num1;

What is the output of the following program?


class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	void SetNumber(int n);
	Number operator ++();
	Number operator ++(int);
};

Number::Number()
{
}

Number::Number(int n)
{
	m_num = n;
}

int Number::GetNumber()
{
	return m_num;
}

void Number::SetNumber(int n)
{
	m_num = n;
}

Number Number::operator ++()
{	
	m_num++;
	return Number(m_num);
}

Number Number::operator ++(int x)
{	
	m_num+=2;
	return Number(m_num);
}

int main()
{
	Number num1(5);
	++num1;
	cout << num1.GetNumber() << endl;	
	num1++;
	cout << num1.GetNumber() << endl;
	return 0;
}

6
77
86
87
9

Given the following code, which will not output the number 15?


class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	void SetNumber(int n);
	Number operator ^(Number num2);
};

Number::Number()
{
}

Number::Number(int n)
{
	m_num = n;
}

int Number::GetNumber()
{
	return m_num;
}

void Number::SetNumber(int n)
{
	m_num = n;
}

Number Number::operator ^(Number num2)
{
	return Number(m_num * num2.m_num);
}

int main()
{
	Number num1(5), num2(3), num3;

	num3 = num2 ^ 5;
	cout << num3.GetNumber() << endl;
	return 0;
}

int main()
{
	Number num1(5), num2(3), num3;

	num3 = num1 ^ 3;
	cout << num3.GetNumber() << endl;
	return 0;
}

int main()
{
	Number num1(5), num2(3), num3;

	num3 = 5 ^ num2;
	cout << num3.GetNumber() << endl;
	return 0;
}

int main()
{
	Number num1(5), num2(3), num3;

	num3 = num1 ^ num2;
	cout << num3.GetNumber() << endl;
	return 0;
}

What advantage is gained by declaring a friend function vs. using public accessor and mutator methods?

It is more efficient to directly access private member variables than use accessor and mutator methods when the friend function truly requires access to these variables.This is the only way to access data members of a class.It is easier and less work for a programmer to access private member variables directly than use accessor and mutator methods.This is the only way to access variables labeled as "protected".

Given the Number class below, how could we add the MoreNumbers class as a friend of the Number class? This will allow code in the MoreNumbers class access to private variables in the Numbers class.


class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
};

class MoreNumbers;

class Number friend MoreNumbers;
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
};

friend MoreNumbers class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
};

class MoreNumbers;

class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	friend class MoreNumbers;
};

class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	friend class MoreNumbers;
};

What is the output of the following code?


class Number
{
private:
	int m_num;
public:
	Number(int n);
	Number();
	int GetNumber();
	void SetNumber(int n);
	Number operator =(Number num2);
	Number operator *(Number num2);
};


Number::Number()
{
}

Number::Number(int n)
{
	m_num = n;
}

int Number::GetNumber()
{
	return m_num;
}

void Number::SetNumber(int n)
{
	m_num = n;
}

Number Number::operator *(Number num2)
{	
	return Number(m_num * num2.m_num);
}

Number Number::operator =(Number num2)
{
	m_num = num2.m_num * 2;
	return Number(m_num);
}

int main()
{
	Number num1(5), num2(3), num3;

	num3 = num1 * num2;
	cout << num3.GetNumber() << endl;
	return 0;
}

1581030

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Chapter 8

Which of the following is not a valid reason to use const in the declaration below? const Money operator +(const Money &amount1, const Money &amount2);

Which of the following prototypes is invalid?

What advantage is gained by declaring a friend function vs. using public accessor and mutator methods?

Which of the following is not a valid reason to use const in the declaration below?
const Money operator +(const Money &amount1, const Money &amount2);