Copy Constructor and Assignment Operator Issues

Question

I am creating a binary linked list for a homework assignment that stores only the degrees of the 1 bits. I can get the highest degree, set bits anywhere in the binary list, and return which bit occurs at a specific degree, but for some reason, I am having the most trouble creating a copy constructor and an assignment (=) operator. Here is the code I have:

// copy constructor
// creates a new linked list where the contents are a deep copy of the provided list
Binary::Binary(const Binary &b)
{
    Binary clone;
    for(BinaryNode* current_other = b.firstTerm; current_other != nullptr; current_other = current_other->next) 
    {
        clone.set_bit(1, current_other->degree); 
    }
}

// assignment operator
// sets the current link list to be a deep copy of the provided list.
// make sure to check if assigning to itself, and make sure to free old memory
// before making the copy.
Binary& Binary::operator=(const Binary &other)
{
    Binary clone;
    for(BinaryNode* current_other = other.firstTerm; current_other != nullptr; current_other = current_other->next) 
    {
        clone.set_bit(1, current_other->degree); 
    }
    return clone;
}

Is my logic faulty on these? Someone please help!

PS I've tested my set_bit(b,d) and other methods so much and I know these are the only ones messing up, because when I try "Binary b3(b2)" or "Binary b3 = b2" the program stops at that point and says "Unhandled exception at 0x00DC4B18 in Assignment 1.exe: 0xC0000005: Access violation reading location 0xCCCCCCD0".

EDIT: I have a default constructor as well: Binary() {firstTerm = nullptr;}

EDIT EDIT:

Output:

    TESTING DEFAULT CONSTRUCTOR
    The binary number b1 is empty.

    TESTING GET AND SET METHODS
    The highest bit of binary number b1 is 5.
    The bit of binary number b1 at degree 5 is 1.
    The bit of binary number b1 at degree 2 is 0.
    The bit of binary number b1 at degree 1 is 0.

    TESTING PARAMETER CONSTRUCTOR
    The bit of binary number b1 at degree 2 is 1.
    The bit of binary number b1 at degree 0 is 1.
    The bit of binary number b1 at degree 1 is 0.

    TESTING COPY CONSTRUCTOR
    B2 = 101
    B3 = _

Unhandled exception at 0x00C04B18 in Assignment 1.exe: 0xC0000005: Access violation reading location 0xCCCCCCD0.

Tester code:

#include <iostream>
#include "binary.h"

using namespace std;

int main (void)
{
    // test default constructor
    Binary b1;
    cout << "TESTING DEFAULT CONSTRUCTOR" << endl;
    if (b1.get_degree() == -1)
        cout << "\tThe binary number b1 is empty." << endl;
    else
        cout << "\tThe binary number b1 is NOT empty. (INCORRECT)" << endl;

    // test get_bit, set_bit, and get_degree
    cout << "\nTESTING GET AND SET METHODS" << endl;
    b1.set_bit(1, 2);
    b1.set_bit(1, 5);
    b1.set_bit(1, 0);
    b1.set_bit(0, 2);
    if (b1.get_degree() == 5)
        cout << "\tThe highest bit of binary number b1 is 5." << endl;
    else
        cout << "\tThe highest bit of binary number b1 is NOT 5. (INCORRECT)" << endl;
    if (b1.get_bit(5) == 1)
        cout << "\tThe bit of binary number b1 at degree 5 is 1." << endl;
    else
        cout << "\tThe bit of binary number b1 at degree 5 is 0. (INCORRECT)" << endl;
    if (b1.get_bit(2) == 0)
        cout << "\tThe bit of binary number b1 at degree 2 is 0." << endl;
    else
        cout << "\tThe bit of binary number b1 at degree 2 is 1. (INCORRECT)" << endl;
    if (b1.get_bit(1) == 0)
        cout << "\tThe bit of binary number b1 at degree 1 is 0." << endl;
    else
        cout << "\tThe bit of binary number b1 at degree 1 is 1. (INCORRECT)" << endl;

    // test parameter constructor
    cout << "\nTESTING PARAMETER CONSTRUCTOR" << endl;
    Binary b2(5);

    if (b2.get_bit(2) == 1)
        cout << "\tThe bit of binary number b2 at degree 2 is 1." << endl;
    else
        cout << "\tThe bit of binary number b2 at degree 2 is 0. (INCORRECT)" << endl;
    if (b2.get_bit(0) == 1)
        cout << "\tThe bit of binary number b2 at degree 0 is 1." << endl;
    else
        cout << "\tThe bit of binary number b2 at degree 0 is 0. (INCORRECT)" << endl;
    if (b2.get_bit(1) == 0)
        cout << "\tThe bit of binary number b2 at degree 1 is 0." << endl;
    else
        cout << "\tThe bit of binary number b2 at degree 1 is 1. (INCORRECT)" << endl;

    // test copy constructor
    cout << "\nTESTING COPY CONSTRUCTOR" << endl;
    cout << "B2= " << b2 << endl;
    b2.set_bit(1,1);
    Binary b3(b2);
    cout << "B3= " << b3 << endl;
    b2.set_bit(1, 1);
    cout << "B2= " << b2 << endl;
    cout << "B3= " << b3 << endl;
    if (b3.get_bit(2) == 1)
        cout << "\tThe bit of binary number b3 at degree 2 is 1." << endl;
    else
        cout << "\tThe bit of binary number b3 at degree 2 is 0. (INCORRECT)" << endl;
    if (b3.get_bit(0) == 1)
        cout << "\tThe bit of binary number b3 at degree 0 is 1." << endl;
    else
        cout << "\tThe bit of binary number b3 at degree 0 is 0. (INCORRECT)" << endl;
    if (b3.get_bit(1) == 0)
        cout << "\tThe bit of binary number b3 at degree 1 is 0." << endl;
    else
        cout << "\tThe bit of binary number b3 at degree 1 is 1. (INCORRECT)" << endl;

    // test assignment operator
    cout << "\nTESTING ASSIGNMENT OPERATOR" << endl;
    b2 = b3;
    b3.set_bit(1, 1);

    if (b2.get_bit(2) == 1)
        cout << "\tThe bit of binary number b2 at degree 2 is 1." << endl;
    else
        cout << "\tThe bit of binary number b2 at degree 2 is 0. (INCORRECT)" << endl;
    if (b2.get_bit(0) == 1)
        cout << "\tThe bit of binary number b2 at degree 0 is 1." << endl;
    else
        cout << "\tThe bit of binary number b2 at degree 0 is 0. (INCORRECT)" << endl;
    if (b2.get_bit(1) == 0)
        cout << "\tThe bit of binary number b2 at degree 1 is 0." << endl;
    else
        cout << "\tThe bit of binary number b2 at degree 1 is 1. (INCORRECT)" << endl;

    // test convert
    cout << "\nTESTING CONVERT METHOD" << endl;
    if (b1.convert() == 33)
        cout << "\tThe decimal value of binary number b1 is 33." << endl;
    else
        cout << "\tThe decimal value of binary number b1 is NOT 33. (INCORRECT)" << endl;

    // test output operator
    cout << "\nTESTING OUTPUT OPERATOR" << endl;
    cout << "\tThe binary number b1 is " << b1 << endl;
    cout << "\tThe number b1 should be 100001" << endl;

    // test addition
    cout << "\nTESTING ADDITION OPERATOR" << endl;
    Binary b4 = b2 + b3;

    if (b4.convert() == 12)
        cout << "\t101 + 111 = 1100." << endl;
    else
        cout << "\t101 + 111 != 1100. (INCORRECT)" << endl;

    // test subtraction
    cout << "\nTESTING SUBTRACTION OPERATOR" << endl;
    Binary b5(b1 - b2);

    if (b5.convert() == 28)
        cout << "\t100001 - 101 = 11100." << endl;
    else
        cout << "\t100001 - 101 != 11100. (INCORRECT)" << endl;

    // test multiplication
    cout << "\nTESTING MULTIPLICATION OPERATOR" << endl;
    Binary b6 = b3 * b2;

    if (b6.convert() == 35)
        cout << "\t111 * 101 = 100011." << endl;
    else
        cout << "\t111 * 101 != 100011. (INCORRECT)" << endl;

    system("pause");
}

binary.h:

#ifndef _BINARY_H_
#define _BINARY_H_

#include <iostream>

class Binary {
private:
    struct BinaryNode {
        int degree;
        BinaryNode* next;
        BinaryNode(int d, BinaryNode* n): degree(d),next(n) {}
    };
    BinaryNode *firstTerm;

public:
    // default constructor
    Binary() {firstTerm = nullptr;}

    // constructor
    // takes a value representing a decimal number and creates
    // the binary linked list representation of it.
    Binary(int x);

    // sets the term with degree d and bit b
    // notice a node is created if bit is 1 AND a node 
    // for that degree doesn't exist, or the node is removed
    // if the bit is 0 AND the node with that degree already exists
    void set_bit(int b, int d);

    // returns one if a term with degree d exists, zero otherwise
    int get_bit(int d) const;

    // returns the decimal integer representation of the binary number.
    int convert() const ;

    // returns the highest degree of any term in the binary number
    // returns -1 if the the list is empty.
    int get_degree() const;

    // destructor
    // make sure that all memory is returned (freed up) correctly
    ~Binary();

    // copy constructor
    // creates a new linked list where the contents are a deep copy of the provided list
    Binary(const Binary &b);

    // assignment operator
    // sets the current link list to be a deep copy of the provided list.
    // make sure to check if assigning to itself, and make sure to free old memory
    // before making the copy.
    Binary& operator=(const Binary &other);

    // prints the binary number to the output stream o
    // please use like:     10001101
    // terms must be printed in descending order of degree
    friend std::ostream& operator<<(std::ostream &o, const Binary &b);

    // returns a new binary number representing the addition of 2 provided binary numbers.
    // do NOT simply convert the numbers to decimal using convert(),add them,
    // then convert back to binary.
    friend Binary operator+(const Binary &b1, const Binary &b2);

    // returns a new binary number representing the subtraction 
    // of 2 provided binary numbers. can assume b1 will always be
    // larger than b2.
    // do NOT simply convert the numbers to decimal using convert(),subtract them,
    // then convert back to binary.
    friend Binary operator-(const Binary &b1, const Binary &b2);

    // returns a new binary number representing the multiplication
    // of 2 provided binary numbers.
    // do NOT simply convert the numbers to decimal using convert(),multiply them,
    // then convert back to binary.
    friend Binary operator*(const Binary &b1, const Binary &b2);

};

std::ostream& operator<<(std::ostream &o, const Binary &b);

Binary operator+(const Binary &b1, const Binary &b2);
Binary operator-(const Binary &b1, const Binary &b2);
Binary operator*(const Binary &b1, const Binary &b2);

#endif

binary.cpp:

#include "binary.h"
using namespace std;

// constructor
// takes a value representing a decimal number and creates
// the binary linked list representation of it.
Binary::Binary(int x)
{
    firstTerm = nullptr;
    int deg = 0; 
    int n = x;
    while (n != 0)
    {
        set_bit(n%2, deg);
        n = n/2;
        ++deg;
    }
}

// sets the term with degree d and bit b
// notice a node is created if bit is 1 AND a node 
// for that degree doesn't exist, or the node is removed
// if the bit is 0 AND the node with that degree already exists
void Binary::set_bit(int b, int d)
{
    if (b == 1)
    {
        if (firstTerm == nullptr || d == 0)
            {
                firstTerm = new BinaryNode(d, firstTerm);
            }

        else
            {
                BinaryNode *current, *prev = firstTerm;
                for(current = firstTerm; current != nullptr; current = current->next)
                {
                    if (current->next == nullptr)
                    {
                        current->next = new BinaryNode(d, nullptr);
                        break;
                    }
                    else if (current->degree == d)
                    {
                        prev->next = new BinaryNode (d, current->next);
                        delete current;
                        break;
                    }
                    else if(current->degree > d)
                    {
                        prev->next = new BinaryNode (d, current);
                        break;
                    }
                    prev = current;
                }
            }
    }
    else
    {
        BinaryNode *current, *prev = firstTerm;
        for(current = firstTerm; current != nullptr; current = current->next)
        {
            if (current->degree == d)
            {
                prev->next = current->next;
                delete current;
                break;
            }
            prev = current;
        }
    }
}

// returns one if a term with degree d exists, zero otherwise
int Binary::get_bit(int d) const
{
    for (BinaryNode *current = firstTerm; current != nullptr; current = current->next)
    {
        if (current == nullptr)
            break;
        if (current->degree == d)
            return 1;
    }
    return 0;
}

// returns the decimal integer representation of the binary number.
int Binary::convert() const
{
    int sum = 0;
    for (BinaryNode* current = firstTerm; current != nullptr; current = current->next)
    {
        sum = sum + (int)pow(2,current->degree);
    }
    return sum;
}

// returns the highest degree of any term in the binary number
// returns -1 if the the list is empty.
int Binary::get_degree() const
{
    if (firstTerm == nullptr)
        {return -1;}
    else
    {
        BinaryNode *current;
        for (current = firstTerm; current->next != nullptr; current = current->next);

        return current->degree;
    }
}

// destructor
// make sure that all memory is returned (freed up) correctly
Binary::~Binary()
{
    BinaryNode* tmp;
    for(BinaryNode* current = firstTerm; current != nullptr; current = tmp) 
    {
            tmp = current->next;
            delete current;
    }
}

// copy constructor
// creates a new linked list where the contents are a deep copy of the provided list
Binary::Binary(const Binary &b)
{
    for(BinaryNode* current_other = b.firstTerm; current_other != nullptr; current_other = current_other->next) 
    {
        set_bit(1, current_other->degree); 
    }
}

// assignment operator
// sets the current link list to be a deep copy of the provided list.
// make sure to check if assigning to itself, and make sure to free old memory
// before making the copy.
Binary& Binary::operator=(const Binary &other)
{
    Binary clone;
    for(BinaryNode* current_other = other.firstTerm; current_other != nullptr; current_other = current_other->next) 
    {
        clone.set_bit(1, current_other->degree); 
    }
    return clone;
}

// prints the binary number to the output stream o
// please use like:     10001101
// terms must be printed in descending order of degree
std::ostream& operator<<(std::ostream &o, const Binary &b)
{
    for(int i = b.get_degree(); i >= 0; --i) 
    {
        o << b.get_bit(i);
    }
    return o;
}

// returns a new binary number representing the addition of 2 provided binary numbers.
// do NOT simply convert the numbers to decimal using convert(),add them,
// then convert back to binary.
Binary operator+(const Binary &b1, const Binary &b2)
{
    int l = b1.get_degree();
    if (b1.get_degree() < b2.get_degree())
    {
        l = b2.get_degree();
    }
    int i, c = 0;
    Binary sum;
    for (i = 0; i <= l; ++i)
    {
        sum.set_bit(((b1.get_bit(i) ^ b2.get_bit(i)) ^ c), i); //get sum (A XOR B XOR C)
        c = ((b1.get_bit(i) & b2.get_bit(i)) | (b1.get_bit(i) &c)) | (b2.get_bit(i) & c); //get carry bit (AB + BC + CA)
    }
    sum.set_bit(c, i);
    return sum;
}

// returns a new binary number representing the subtraction 
// of 2 provided binary numbers. can assume b1 will always be
// larger than b2.
// do NOT simply convert the numbers to decimal using convert(),subtract them,
// then convert back to binary.
Binary operator-(const Binary &b1, const Binary &b2)
{
    Binary one = Binary(1);
    Binary inv, two, result, fresult;
    int i, l = b2.get_degree() + 1;
    for(i = 0; i <= l; ++i)
    {
        if (b2.get_bit(i) == 1)
            inv.set_bit(0,i);
        else
            inv.set_bit(1,i);
    }
    two = inv + one;
    result = two + b1;
    if (b1.get_degree() > l)
    {
        l = b1.get_degree();
    }
    for (l; l >= 0; l--)
    {
        fresult.set_bit(result.get_bit(l), l);
    }
    return (fresult);
}

// returns a new binary number representing the multiplication
// of 2 provided binary numbers.
// do NOT simply convert the numbers to decimal using convert(),multiply them,
// then convert back to binary.
Binary operator*(const Binary &b1, const Binary &b2)
{
    Binary prod = b1;
    for (int i = 1; i < b2.convert(); ++i)
    {
        prod = prod + b1;
    }
    return prod;
}

Answer 1

Binary::Binary(const Binary &b)
{
    Binary clone;
    for(BinaryNode* current_other = b.firstTerm; current_other != nullptr; current_other = current_other->next) 
    {
        clone.set_bit(1, current_other->degree); 
    }
}

You create an object called clone , set its bits, and then throw it away. That doesn't seem right. Perhaps you mean:

Binary::Binary(const Binary &b)
{
    for(BinaryNode* current_other = b.firstTerm; current_other != nullptr; current_other = current_other->next) 
    {
        set_bit(1, current_other->degree); 
    }
}

Answer 2

I figured it out, thanks for your help everyone. I figured out my problem. In the copy constructor, as someone pointed out, I believe, I hadn't declared firstTerm yet, as I had to in the other constructors. The final code ended up as:

Binary::Binary(const Binary &b)
{
    firstTerm = nullptr; //construct firstTerm
    for(BinaryNode* current_other = b.firstTerm; current_other != nullptr; current_other = current_other->next) 
    //set a node pointer = to b's firstTerm then go through b's list, setting each bit and degree to the new list
    {
        set_bit(1, current_other->degree); //only 1 bits exist in this list, so you'll only set one bits at each degree
    }   
}

In the assignment operator, I wasn't destructing the current list first, if needed, or making sure that it wasn't copying to itself. Also, I had the & in the wrong place. The final code ended up as:

Binary &Binary::operator=(const Binary &other)
{
    if(this != &other) //make sure it isn't copying to itself
    {
        if (this->get_degree() != -1) //if the Binary list isn't empty, destruct it
        {
            this->~Binary();
        }
        firstTerm = nullptr; //construct firstTerm
        for(BinaryNode* current_other = other.firstTerm; current_other != nullptr; current_other = current_other->next) 
        //set a node pointer = to other's firstTerm then go through other's list, setting each bit and degree to the new list
        {
            set_bit(1, current_other->degree); //only 1 bits exist in this list, so you'll only set one bits at each degree
        }   

        return *this;
    }
}

Answer 3

A soon as you define a constructor, the compiler won't generate a default constructor for you, this means you can't do Binary clone; if you haven't defined a Binary::Binary() constructor.