Only the signed extension function is passing, even though Twos complement is outputting correctly.

#include

#include

#include

using namespace std;

int binary_to_decimal_signed(string s);

// precondition: s is a string that consists of only 0s and 1s

// postcondition: the decimal integer that is represented by s in two's complement

string signed_extension(string s);

// precondition: s is a string that consists of only 0s and 1s that is at most 16 bits

// postcondition: a 16 bit string has been returned as signed extension of s. For instance, if s = "0101" then

// return value will be "00000000000000000101" total 12 0s are added in front of s

string decimal_to_binary_signed(int n);

// precondition: n is an integer

// postcondition: ns two's complement binary representation is returned as a string of 0s and 1s

string add_binaries_signed(string b1, string b2);

// precondition: b1 and b2 are strings that consists of 0s and 1s at most 32 bits, i.e.

// b1 and b2 are two's complement binary representations of two integers. "0" is 0, "1" is -1

// However, "10" will be consider as "1111111111111110" as -2

// postcondition: the sum of b1 and b2 is returned as (up to) 32 bits two's complement representation.

// For instance, if b1 = 1101 (-3), b2 = 01 (+1), then the return value is 1111111111111110 (-2)

string twos_complement(string s);

// precondition: s is a string that consists of only 0s and 1s

// postcondition: two's complement of s is returned as an 16 bits binary integer. For instance, if s = "1101", then

// return value will be "1111111111111101"

int binary_to_decimal(string s);

// precondition: s is a string that consists of only 0s and 1s

// postcondition: the positive decimal integer that is represented by s

string decimal_to_binary(int n);

// precondition: n is a positive integer

// postcondition: ns binary representation is returned as a string of 0s and 1s

string add_binaries(string b1, string b2);

// precondition: b1 and b2 are strings that consists of 0s and 1s, i.e.

// b1 and b2 are binary representations of two positive integers

// postcondition: the sum of b1 and b2 is returned. For instance,

// if b1 = 11, b2 = 01, then the return value is 100

void menu();

// display the menu. Student shall not modify this function

int grade();

// returns an integer that represents the students grade of this projects.

// Student shall NOT modify

bool is_binary(string b);

// returns true if the given string s consists of only 0s and 1s; false otherwise

bool test_binary_to_decimal_signed();

// returns true if the students implementation of binary_to_decimal function

// is correct; false otherwise. Student shall not modify this function

bool test_decimal_to_binary_signed();

// returns true if the students implementation of decimal_to_binary function is correct; false otherwise. Student shall not modify this function

bool test_add_binaries_signed();

// which returns true if the students implementation of add_binaries function

// is correct; false otherwise. Student shall not modify this function

bool test_signed_extension();

// return true if the student's implementation of sign_extension function

// is correct; false otherwise. Student shall not modify this function

bool test_twos_complement();

// return true if the student's implementation of twos_complement function

// is correct; false otherwise. Student shall not modify this function

int main()

{

int choice;

string b1, b2;

int x, score;

do{

// display menu

menu();

cout << "Enter your choice: ";

cin >> choice;

// based on choice to perform tasks

switch(choice){

case 1:

cout << "Enter a binary string: ";

cin >> b1;

if(!is_binary(b1))

cout << "It is not a binary number ";

else

cout << "Its decimal value is: " << binary_to_decimal_signed(b1) << endl;

break;

case 2:

cout << "Enter an integer: ";

cin >> x;

cout << "Its binary representation is: " <

break;

case 3:

cout << "Enter two binary numbers, separated by white space: ";

cin >> b1 >> b2;

if(!is_binary(b1) || !is_binary(b2))

cout << "At least one number is not a binary" << endl;

else

cout << "The sum is: " << add_binaries_signed(b1, b2) << endl;

break;

case 4:

cout << "Enter a binary number: ";

cin >> b1;

cout << "Its signed extension to 16 bits is: " << signed_extension(b1) << endl;;

break;

case 5:

cout << "Enter a binary number: ";

cin >> b1;

cout << "Its two's complement is: " << twos_complement(b1) << endl;

break;

case 6:

score = grade();

cout << "If you turn in your project on blackboard now, you will get " << score << " out of 10" << endl;

cout << "Your instructor will decide if one-two more points will be added or not based on your program style, such as good commnets (1 points) and good efficiency (1 point)" << endl;

break;

case 7:

cout << "Thanks for using binary calculator program. Good-bye" << endl;

break;

default:

cout << "Wrong choice. Please choose 1-5 from menu" << endl;

break;

}

}while(choice != 7);

return 0;

}

string signed_extension(string s){

// you implement this one first

int n = s.length();

int k = 16 - n;

string result = "";

if (s[0] == '0') {

for (int i = 0; i < k; i++) {

result += "0";

}

} else {

for (int i = 0; i < k; i++) {

result += "1";

}

}

result += s;

return result;

}

int binary_to_decimal_signed(string s){

for (int i = 0; i < s.size(); i++) {

assert(s[i] == '0' || s[i] == '1');

}

int result = 0;

int sign = (s[0] == '1') ? -1 : 1;

for (int i = 0; i < s.size(); i++) {

if (s[i] == '1') {

result += (1 << (s.size() - i - 1));

}

}

return result * sign;

}

string decimal_to_binary_signed(int n){

// you implement this one fourth

string result = "";

int bits = 16;

if (n < 0) {

result = '1';

n = ~n + 1;

} else {

result = '0';

}

for (int i = 0; i < bits - 1; i++) {

if (n & (1 << (bits - i - 2))) {

result += '1';

} else {

result += '0';

}

}

return result;

}

string add_binaries_signed(string b1, string b2){

// you implement this one fifth

string result = "";

int carry = 0;

int n = b1.length();

int m = b2.length();

// sign extension for both numbers

if(n < 32) b1 = string(32 - n, b1[0] == '1' ? '1' : '0') + b1;

if(m < 32) b2 = string(32 - m, b2[0] == '1' ? '1' : '0') + b2;

// add each bit with carry

for(int i = 31; i >= 0; i--){

int sum = (b1[i] - '0') + (b2[i] - '0') + carry;

result = char(sum % 2 + '0') + result;

carry = sum / 2;

}

return result;

}

string twos_complement(string s){

int n = s.length();

string result = "";

bool carry = 1;

for (int i = n - 1; i >= 0; i--) {

if (s[i] == '0' && carry) {

result = '0' + result;

carry = 0;

} else if (s[i] == '1' && carry) {

result = '0' + result;

} else if (s[i] == '0' && !carry) {

result = '1' + result;

carry = 0;

} else {

result = '1' + result;

carry = 1;

}

}

while (result.length() < 16) {

result = '0' + result;

}

return result;

}