module 6

Question 1

The following operation \_\_\_\_\_\_\_\_ the bit:

b & 1 == b

Answer 1

reads

Question 2

The following operation \_\_\_\_\_\_\_\_ the bit:

b | 1 == 1

Answer 2

sets

Question 3

The following operation \_\_\_\_\_\_\_\_ the bit:

b & 0 == 0

Answer 3

resets

Question 4

The following operation \_\_\_\_\_\_\_\_ the bit:

b ^ 1 == ~b

Answer 4

flips

Question 5

Write a line of code that will form a 1 mask with the 1 at bit position n

Answer 5

unsigned int mask = 1u << n;

Question 6

Write a line of code to test if a bit is set at position n of x:

unsigned int mask = 1u << n;

Answer 6

bool is_set = !!(x & mask);

Question 7

Write a line of code to set the bit at position n of x using this mask:

unsigned int mask = 1u << n;

Answer 7

x |= mask;

Question 8

Write a line of code to set all bits of x

Answer 8

x = ~0u;

Question 9

Write a mask, then use that mask to set all the bits of x below position n

Answer 9

mask = (1u << n) - 1;
x &= mask;

Question 10

Write a mask, then use that mask to set all the bits of x between position m and position n (inclusive)

Answer 10

mask = ((1u << ( n - m + 1)) - 1) << m;
x &= mask;

Question 11

Write a mask, then use the mask to reset a single bit of x at position n

Answer 11

unsigned int mask = ~(1u << n);
x &= mask;

Question 12

Write a line of code to flip the bit at position n of x using this mask:

unsigned int mask = 1u &laquo_space;n;

Answer 12

x ^= mask;

Question 13

Extract bits m through n of x as a number

Answer 13

mask = ((1u << ( n - m + 1)) - 1) << m;
unsigned int new_num = (x & mask) >> m;

Question 14

Write a line of code to swap the internal data of these two vectors:

vector<string> svec1(10);
vector<string> svec2(24);

Answer 14

swap(svec1, svec2);

exchanges internal data including pointers, a shallow exchange

Question 15

adding elements

Answer 15

• c.push_back(t) - creates an element with the value t at the end of c
• c.emplace_back(args) - constructs an element from the args at the end of t
• c.push_front(t) - creates an element with the value t at the front of c
• c.emplace_back(args) - constructs an element from the args at the front of c
• c.insert(p, t) - creates an element with the value t, and places it before the element denoted by the iterator p, returns an iterator to the added element
• c.emplace(p, args) - constructs an element from the args, and places it before the element denoted by the iterator p, returns an iterator to the added element
• c.insert(p, n, t) - inserts n elements with the value t, and places it before the element denoted by the iterator p, returns an iterator to the first element inserted
• c.insert(p, b, e) - inserts elements from the range denoted by the iterators b and e, and places it before the element denoted by the iterator p, returns an iterator to the first element inserted
• c.insert(p, i]) - i] is a braced list fo element values, inserts the given values before the element denoted by the iterator p, returns an iterator to the first element inserted

Question 16

Insert the string “Hello!” at the beginning of the vector and the list:

vector<string> svec;
list<string> slist;

Answer 16

slist.insert(slist.begin(), "Hello!);
svec.insert(svec.begin(), "Hello!);

Question 17

Erasing Elements

Answer 17

• c.pop_back() - removes the last element in c, returns void
• c.pop_front - removes the first element in c, returns void
• c.erase(p) - removes the element donoted by the iterator p, and returns an iterator to the element after the one deleted
• c.erase(b, e) - removes the range of elements denoted by the iterators b and e, and returns an iterator to the element after the last one deleted
• c.clear() - removes all elements in c, returns void

Question 18

Managing Container Size

Answer 18

• c.resize(n) - resize c so that it has n elements
• c.resize(n, t) - resize c so that is has n elements, any elements added have value t.
• c.shrink_to_fit() - request to reduce capacity() to equal size() only for vector, string, and deque
• c.capacity() - number of elements c can have before reallocation is necessary, only for vector and string
• c.reserve(n) - allocate space for at least n elements, only for vector and string

Question 19

given the following class C, write a move constructor:

#include <iostream>
using namespace std;

class C {
public:
    C() = default;
    C(const C&) {cout << "copy constructor\n";}
    C& operator=(const C&) {
        cout << "copy assignment\n";
        return *this;
    }
};

Answer 19

C(C&&) {cout << "move constructor\n";}

Question 20

given the following class C, write a move assignment:

#include <iostream>
using namespace std;

class C {
public:
    C() = default;
    C(const C&) {cout << "copy constructor\n";}
    C& operator=(const C&) {
        cout << "copy assignment\n";
        return *this;
    }
};

Answer 20

    C& operator=(C&&) {
        cout << "move assignment\n";
        return *this;
    }

Question 21

Given the following code, what is the output of the marked line in main()?

#include <iostream>
using namespace std;

class C {
public:
    C() = default;
    C(const C&) {cout << "copy constructor\n";}
    C(C&&) {cout << "move constructor\n";}
    C& operator=(const C&) {
        cout << "copy assignment\n";
        return *this;
    }
    C& operator=(C&&) {
        cout << "move assignment\n";
        return *this;
    }
};
C g() {return C();}
void f(C) {}

int main() {
    C c;
    C c2(c);     // output?
    c = c2;
    c = g();
    f(c);
    f(g());
    f(std::move(g()));
}

Answer 21

copy constructor

Question 22

Given the following code, what is the output of the marked line in main()?

#include <iostream>
using namespace std;

class C {
public:
    C() = default;
    C(const C&) {cout << "copy constructor\n";}
    C(C&&) {cout << "move constructor\n";}
    C& operator=(const C&) {
        cout << "copy assignment\n";
        return *this;
    }
    C& operator=(C&&) {
        cout << "move assignment\n";
        return *this;
    }
};
C g() {return C();}
void f(C) {}

int main() {
    C c;
    C c2(c);
    c = c2;     // output?
    c = g();
    f(c);
    f(g());
    f(std::move(g()));
}

Answer 22

copy assignment

Question 23

Given the following code, what is the output of the marked line in main()?

#include <iostream>
using namespace std;

class C {
public:
    C() = default;
    C(const C&) {cout << "copy constructor\n";}
    C(C&&) {cout << "move constructor\n";}
    C& operator=(const C&) {
        cout << "copy assignment\n";
        return *this;
    }
    C& operator=(C&&) {
        cout << "move assignment\n";
        return *this;
    }
};
C g() {return C();}
void f(C) {}

int main() {
    C c;
    C c2(c);
    c = c2;
    c = g();     // output?
    f(c);
    f(g());
    f(std::move(g()));
}

Answer 23

move assignment

Question 24

Given the following code, what is the output of the marked line in main()?

#include <iostream>
using namespace std;

class C {
public:
    C() = default;
    C(const C&) {cout << "copy constructor\n";}
    C(C&&) {cout << "move constructor\n";}
    C& operator=(const C&) {
        cout << "copy assignment\n";
        return *this;
    }
    C& operator=(C&&) {
        cout << "move assignment\n";
        return *this;
    }
};
C g() {return C();}
void f(C) {}

int main() {
    C c;
    C c2(c);
    c = c2;
    c = g();
    f(c);        // output?
    f(g());
    f(std::move(g()));
}

Answer 24

copy constructor

Question 25

Given the following code, what is the output of the marked line in `main()`? ``` #include using namespace std; class C { public: C() = default; C(const C&) {cout << "copy constructor\n";} C(C&&) {cout << "move constructor\n";} C& operator=(const C&) { cout << "copy assignment\n"; return *this; } C& operator=(C&&) { cout << "move assignment\n"; return *this; } }; C g() {return C();} void f(C) {} int main() { C c; C c2(c); c = c2; c = g(); f(c); f(g()); f(std::move(g())); // output? } ```

Answer 25

move constructor