Hexadecimal Calculator for Addition and Subtraction - c++

Question

I have an issue with my program which is used to calculate addition and subtraction for Hexadecimals. The algorithm of my program is:
Take 2 strings inputted by the user, and "+" or "-" depending on the
operator they chose
Convert the 2 strings into decimals, and add or subtract
If the second number is bigger, use the bigger number to subtract the smaller number, and put a "-" in front of it when returning the result
(1 - 8 should = -7, but instead, I take 8 - 1 = 7, and return "-" and "7" so it gives "-7)
Take the decimal result from the operation and convert back to hexadecimal
Return string of hexadecimal
However, I have run into a issue where my calculations give me wrong answers.
(For e.g FFFFFF + FFFFFFFFFF prints "FFFFFFE" instead of "10000FFFFFE")
What can I do to solve the issue?
I created my own Power function for this program as I need a a number that can go up to 16 Fs for the Hexadecimal string.
Power Function:
unsigned long long int result = 1;
int i;
for (i = 0; i < y; i++)
{
result *= x;
}
return result;
Code:
int i;
int power = FirstHexaNumber.length() - 1;
int power2 = SeconHexaNumber.length() - 1;
int checkLength = FirstHexaNumber.length();
int checkLength2 = SeconHexaNumber.length();
unsigned long long int decimalNumber = 0;
unsigned long long int decimalNumber2 = 0;
unsigned long long int totalDecimal;
int temporary;
string result;
if (Operator == '+') //check if operator is add or minus
{
//Convert Hex to Decimal for first number
for (i = 0; i < checkLength; i++)
{
if (int(FirstHexaNumber[i]) >= 48 && int(FirstHexaNumber[i]) <= 57) { // check if FirstHexaNumber 0 to 9
decimalNumber += ((int(FirstHexaNumber[i])) - 48) * powerFunc(16, power); //formula to convert hexadecimal into decimal, int(FirstHexaNumber[i]) is used to convert hexa into a number
}
else if (int(FirstHexaNumber[i]) >= 65 && int(FirstHexaNumber[i]) <= 70) // check if FirstHexaNumber is A to F
{
decimalNumber += ((int(FirstHexaNumber[i])) - 55)*powerFunc(16, power);
}
else if (int(FirstHexaNumber[i]) >= 97 && int(FirstHexaNumber[i]) <= 102) // check if FirstHexaNumber is a to f
{
int x = powerFunc(16, power);
decimalNumber += ((int(FirstHexaNumber[i])) - 87)* x;
}
power--; //power-- since it starts from "HexaNumber.length - 1". Power should decrease as assignment of power goes down
}
//Convert Hex to Decimal for second number
for (i = 0; i < checkLength2; i++)
{
if (int(SeconHexaNumber[i]) >= 48 && int(SeconHexaNumber[i]) <= 57) {
decimalNumber2 += ((int(SeconHexaNumber[i])) - 48) * powerFunc(16, power2); //formula to convert Hexadecimal to Decimal
}
else if (int(SeconHexaNumber[i]) >= 65 && int(SeconHexaNumber[i]) <= 70)
{
decimalNumber2 += ((int(SeconHexaNumber[i])) - 55)*powerFunc(16, power2); //formula to convert Hexadecimal to Decimal
}
else if (int(SeconHexaNumber[i]) >= 97 && int(SeconHexaNumber[i]) <= 102)
{
unsigned long long int x = powerFunc(16, power2);
decimalNumber2 += ((int(SeconHexaNumber[i])) - 87)*x; //formula to convert Hexadecimal to Decimal
}
power2--;
}
totalDecimal = decimalNumber + decimalNumber2; //Adds the total decimal to convert into hexadecimal
if (totalDecimal == 0)
{
return "0";
}
//Converts Decimal to Hexadecimal
for (i = 0; totalDecimal != 0; i++) //as long as totalDecimal does not hit 0 from being divided by 16, run the loop
{
temporary = totalDecimal % 16; //use temporary as a variable to temporarily hold onto the number remainder of mod 16
if (temporary >= 10) //if temporary >= 10, that means it needs to be converted to alphabet
{
result.insert(0, 1, temporary + 55); //result.insert inserts a string of text into a spot, and pushes everything else backwards.
} //in this case, result.insert assigns "temporary+55" into the spot of characters 0 to 1.
else //else, it means that the decimal will be a number, add 48 to convert to ascii
{
result.insert(0, 1, temporary + 48);
}
totalDecimal = totalDecimal / 16; //divide by 16 to move on to finding the next digit/alphabet
}
return result;
}
else if (Operator == '-') //check if operator is add or minus
{
//Convert Hex to Decimal for first number
for (i = 0; i < checkLength; i++) //as long as the loop does not exceed the length of the hexadecimal, run it
{
if (int(FirstHexaNumber[i]) >= 48 && int(FirstHexaNumber[i]) <= 57) {
decimalNumber += ((int(FirstHexaNumber[i])) - 48) * powerFunc(16, power);
}
else if (int(FirstHexaNumber[i]) >= 65 && int(FirstHexaNumber[i]) <= 70)
{
decimalNumber += ((int(FirstHexaNumber[i])) - 55)*powerFunc(16, power);
}
else if (int(FirstHexaNumber[i]) >= 97 && int(FirstHexaNumber[i]) <= 102)
{
decimalNumber += ((int(FirstHexaNumber[i])) - 87)*powerFunc(16, power);
}
power--;
}
//Convert Hex to Decimal for second number
for (i = 0; i < checkLength2; i++)
{
if (int(SeconHexaNumber[i]) >= 48 && int(SeconHexaNumber[i]) <= 57) {
decimalNumber2 += ((int(SeconHexaNumber[i])) - 48) * powerFunc(16, power2);
}
else if (int(SeconHexaNumber[i]) >= 65 && int(SeconHexaNumber[i]) <= 70)
{
decimalNumber2 += ((int(SeconHexaNumber[i])) - 55)*powerFunc(16, power2);
}
else if (int(SeconHexaNumber[i]) >= 97 && int(SeconHexaNumber[i]) <= 102)
{
decimalNumber2 += ((int(SeconHexaNumber[i])) - 87)*powerFunc(16, power2);
}
power2--;
}
if (decimalNumber >= decimalNumber2)
{
totalDecimal = decimalNumber - decimalNumber2; //subtract bigger number by smaller number.
if (totalDecimal == 0)
{
return "0";
}
for (i = 0; totalDecimal != 0; i++)
{
temporary = totalDecimal % 16;
if (temporary >= 10)
{
result.insert(0, 1, temporary + 55);
}
else
{
result.insert(0, 1, temporary + 48);
}
totalDecimal = totalDecimal / 16;
}
return result;
}
else
{
totalDecimal = decimalNumber2 - decimalNumber; //subtract bigger number by smaller number.
if (totalDecimal == 0)
{
return "0";
}
for (i = 0; totalDecimal != 0; i++)
{
temporary = totalDecimal % 16;
if (temporary >= 10)
{
result.insert(0, 1, temporary + 55);
}
else
{
result.insert(0, 1, temporary + 48);
}
totalDecimal = totalDecimal / 16;
}
return "-" + result;
}
}
return 0;

Answer 1

You can try this snippet:
int a,b;
cout << "\nEnter A in hex: ";
cin >> hex >> a;
cout << "\nEnter B in hex: ";
cin >> hex >> b;
cout << "\n Addition of " << hex << a <<" and "<< hex << b << " is " << hex << a+b;
cout << "\n Substraction of " << hex << a << " and " << hex << b << " is " << hex << a - b;

Answer 2

int x = powerFunc(16, power); should be long long x = powerFunc(16, power);
Don't know full source of the function pow, the return type should be long long too.
Hexadecimal Calculator can be more simple.
#include <sstream>
std::stringstream ss1(s1),ss2(s2);
ss1 >> std::hex >> i1;
ss2 >> std::hex >> s2;
std::cout << std::hex << std::uppercase << i1 + s2 << std::endl;
std::stringstream res;
res << std::hex << std::uppercase << i1 + i2;
return res.str();