Chapter 16

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Chapter 16

Templates

This activity contains 10 questions.

What is a more generalizable and compact way to implement the following functions that compute the Absolute Value?


int AbsoluteValue(int i)
{
	if (i<0) return -1 * i;
	return i;
}

float AbsoluteValue(float f)
{
	if (f<0) return -1 * f;
	return f;
}

template<class T>
T AbsoluteValue(T val)
{
	if (val<0) return -1 * val;
	return val;
}

This is the only way to write the functions.

int AbsoluteValue(template<int,float> val)
{
	if (val<0) return -1 * val;
	return val;
}

Object AbsoluteValue(Object val)
{
	if (val<0) return -1 * val;
	return val;
}

What will the following program output when it is run?


template<class T>
void swapValues(T &var1, T &var2)
{
	T temp;

	temp = var1;
	var1 = var2;
	var2 = temp;
}

class MyInt
{
private:
	int *pInt;
public:
	MyInt();
	MyInt(int num);
	~MyInt();
	int getVal();
};

MyInt::MyInt()
{
	pInt = new int;
	*pInt = 0;
}

MyInt::MyInt(int num)
{
	pInt = new int;
	*pInt = num;
}

MyInt::~MyInt()
{
	delete pInt;
}

int MyInt::getVal()
{
	return *pInt;
}

int main()
{	
	MyInt myX(1), myY(2);

	swapValues(myX, myY);
	cout << myX.getVal() << " " << 
	   myY.getVal() << endl;
	
	return 0;
}

2 (unknown value)

The program will likely crash upon exit. 2 1 The program will crash upon executing the swapValues routine. 1 2

What will the following program output when run?


template<class T>
void swapValues(T &var1, T &var2)
{
	T temp;

	temp = var1;
	var1 = var2;
	var2 = temp;
}

class MyInt
{
private:
	int *pInt;
public:
	MyInt();
	MyInt(int num);
	~MyInt();
	int getVal();
	MyInt& operator =(MyInt &myInt2);
};

MyInt::MyInt()
{
	pInt = new int;
	*pInt = 0;
}

MyInt::MyInt(int num)
{
	pInt = new int;
	*pInt = num;
}

MyInt::~MyInt()
{
	delete pInt;
}

int MyInt::getVal()
{
	return *pInt;
}

MyInt& MyInt::operator =(MyInt &myInt2)
{
	*pInt = *(myInt2.pInt);
	return *this;
}

// Main class
int main()
{	
	MyInt myX(1), myY(2);


	swapValues(myX, myY);
	cout << myX.getVal() << " " 
	   << myY.getVal() << endl;
	
	return 0;
}

1 22 (unknown value)

The program will likely crash upon exit. The program will crash upon executing the swapValues routine. 2 1

What is the difference between:


1. template<typename T>
and
2. template<class T>

#1 is used to define a type while #2 is used to declare a template variable.There is no difference, although most programmers tend to use "class" instead of "typename".#1 only works on primitive data types while #2 only works on classes.#1 only works on integer data types while #2 only works on classes.

What is the difference between:


vector<int>* pVec1;
  and
vector<int *> pVec2;

pVec1 is a vector of pointers to integers. We can push_back integers and C++ will allocate memory for them in the vector.

pVec2 is a pointer to a vector of integers. Memory for the vector must be allocated before pVec1 may be accessed. pVec1 is a vector of pointers to integers. We can push_back addresses of integers that have been allocated in memory.

pVec2 is a pointer to a vector of integers. Memory for the vector must be allocated before pVec1 may be accessed. pVec1 is a pointer to a vector of integers. Memory for the vector must be allocated before pVec1 may be accessed.

pVec2 is a vector of pointers to integers. We can push_back addresses of integers that have been allocated in memory. pVec1 is a pointer to a vector of integers. Memory for the vector must be allocated before pVec1 may be accessed.

pVec2 is a vector of pointers to integers. We can push_back integers and C++ will allocate memory for them in the vector.

Is the following declaration valid?


vector<vector<double>> dVec;

No, C++ will confuse >> with the stream extraction operator.Yes, this is a valid declaration.No, to nest vectors we must define a separate type for the nested vector and us it.No, it is not valid to nest vectors.

Which of the following is the simplest way to legally define a class to handle sets using class templates?

template<class T>
class Set
{
	private:
		vector<T> data;
	public:
		Set();
		void Add(T item);
		bool Member(T item);
};

template<class T>
Set<T>::Set()
{
}

template<class T>
void Set<T>::Add(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return;
	}
	data.push_back(item);
}

template<class T>
bool Set<T>::Member(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return true;
	}
	return false;
}

template<class T>
class Set
{
	private:
		vector<T> data;
	public:
		Set();
		void Add(T item);
		bool Member(T item);
};

template<class T>
Set::Set()
{
}

template<class T>
void Set::Add(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return;
	}
	data.push_back(item);
}

template<class T>
bool Set::Member(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return true;
	}
	return false;
}

template<class T>
class Set
{
	private:
		vector<T> data;
	public:
		Set();
		void Add(T item);
		bool Member(T item);
};

Set<T>::Set()
{
}

void Set<T>::Add(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return;
	}
	data.push_back(item);
}

bool Set<T>::Member(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return true;
	}
	return false;
}

template<class T>
class Set
{
	private:
		vector<T> data;
	public:
		Set();
		void Add(T item);
		bool Member(T item);
};

Set::Set()
{
}

void Set::Add(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return;
	}
	data.push_back(item);
}

bool Set::Member(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return true;
	}
	return false;
}

Given the template below:


template<class T>
class Set
{
	private:
		vector<T> data;
	public:
		Set();
		void Add(T item);
		bool Member(T item);
};

template<class T>
Set<T>::Set()
{
}

template<class T>
void Set<T>::Add(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return;
	}
	data.push_back(item);
}

template<class T>
bool Set<T>::Member(T item)
{
	for (int i=0; i<data.size(); i++) {
		if (data[i]==item) return true;
	}
	return false;
}

Which of the following is a valid main() function?

int main()
{	
	Set s<int>;

	s.Add(3);
	s.Add(4);
	s.Add(55);
	cout << s.Member(3) << endl;
	cout << s.Member(44) << endl;
	cout << s.Member(55) << endl;
	return 0;
}

int main()
{	
	Set s;

	s.Add(3);
	s.Add(4);
	s.Add(55);
	cout << s.Member(3) << endl;
	cout << s.Member(44) << endl;
	cout << s.Member(55) << endl;
	return 0;
}

int main()
{	
	Set<int> s;

	s.Add(3);
	s.Add(4);
	s.Add(55);
	cout << s.Member(3) << endl;
	cout << s.Member(44) << endl;
	cout << s.Member(55) << endl;
	return 0;
}

int main()
{	
	template<class int>
	Set s;

	s.Add(3);
	s.Add(4);
	s.Add(55);
	cout << s.Member(3) << endl;
	cout << s.Member(44) << endl;
	cout << s.Member(55) << endl;
	return 0;
}

How can we define a template with two type parameters?

template<class T1, T2>template<class T1, class T2>template<class T1>
template<class T2>It is only possible to have a single type in a template.

Given the following class definition:


template<class T>
class Set
{
	private:
		vector<T> data;
	public:
		Set();
		void Add(T item);
		bool Member(T item);
};

Which of the following is a correctly defined derived class with a constructor?

class NamedSet : public Set
{
	public:
		string name;
		NamedSet();
};

NamedSet::NamedSet() : Set()
{
	name = "None";
}

template<class T>
class NamedSet : public Set<T>
{
	public:
		string name;
		NamedSet();
};

template<class T>
NamedSet<T>::NamedSet() : Set<T>()
{
	name = "None";
}

template<class T>
class NamedSet : public Set
{
	public:
		string name;
		NamedSet();
};

template<class T>
NamedSet<T>::NamedSet() : Set()
{
	name = "None";
}

template<class T>
class NamedSet : public Set<T>
{
	public:
		string name;
		NamedSet();
};

template<class T>
NamedSet<T>::NamedSet() : Set()
{
	name = "None";
}

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Chapter 16

What is a more generalizable and compact way to implement the following functions that compute the Absolute Value?
int AbsoluteValue(int i) { if (i<0) return -1 * i; return i; } float AbsoluteValue(float f) { if (f<0) return -1 * f; return f; }

What is the difference between:
1. template<typename T> and 2. template<class T>

What is the difference between:
vector<int>* pVec1; and vector<int *> pVec2;

Is the following declaration valid?
vector<vector<double>> dVec;

Which of the following is the simplest way to legally define a class to handle sets using class templates?

How can we define a template with two type parameters?

Given the following class definition:
template<class T> class Set { private: vector<T> data; public: Set(); void Add(T item); bool Member(T item); };
Which of the following is a correctly defined derived class with a constructor?

Chapter 16

What is a more generalizable and compact way to implement the following functions that compute the Absolute Value? int AbsoluteValue(int i) { if (i<0) return -1 * i; return i; } float AbsoluteValue(float f) { if (f<0) return -1 * f; return f; }

What is the difference between: 1. template<typename T> and 2. template<class T>

What is the difference between: vector<int>* pVec1; and vector<int *> pVec2;

Is the following declaration valid? vector<vector<double>> dVec;

Which of the following is the simplest way to legally define a class to handle sets using class templates?

How can we define a template with two type parameters?

Given the following class definition: template<class T> class Set { private: vector<T> data; public: Set(); void Add(T item); bool Member(T item); }; Which of the following is a correctly defined derived class with a constructor?

What is a more generalizable and compact way to implement the following functions that compute the Absolute Value?
int AbsoluteValue(int i) { if (i<0) return -1 * i; return i; } float AbsoluteValue(float f) { if (f<0) return -1 * f; return f; }

What is the difference between:
1. template<typename T> and 2. template<class T>

What is the difference between:
vector<int>* pVec1; and vector<int *> pVec2;

Is the following declaration valid?
vector<vector<double>> dVec;

Given the following class definition:
template<class T> class Set { private: vector<T> data; public: Set(); void Add(T item); bool Member(T item); };
Which of the following is a correctly defined derived class with a constructor?