converting '-' char to int array for hugeInteger

[AZRebelCowgirl73]

I am trying to accomodate for negative numbers, and as long as the negative is not being used, I have no problems with my input() ouput() and add() functions. I have tried this two different ways, one with and one without a switch statement to convert negatives. I will show my input() both ways and the char convert() for the latter of the two. With the first -1234 prints -31234 because subtracting '0' results in a -3 for '-', the second way deletes the - completely and -1234 prints 1234.

void HugeInteger::input()
{
      char line[41];      //characters read in to hold integer values
      
      cout << "\nEnter Huge Integer (Max: 40 digits): ";
      cin.getline(line, sizeof line);

      inputSize = strlen(line);      //determine size of users integer

      if (inputSize > arraySize)      //make sure no more than 40 digits where entered
            cout << "\nThe integer entered was to long.  Array not initialized." << endl;
      else
            for (int loopSize = 0; loopSize < inputSize; loopSize++)
                  //subtract ASCII value for '0' to get raw value
				  //store digits at end of 40 digit array all non initialized parts of array stay a 0
                  bigNumber[(arraySize - 1) - loopSize] = line[(inputSize- 1) - loopSize] - '0';

}

and the second design is:

void HugeInteger::input()
{
    char line[41];      //characters read in to hold integer values
      
    cout << "\nEnter Huge Integer (Max: 40 digits): ";
    cin.getline(line, sizeof line);

    inputSize = strlen(line);      //determine size of users integer

    if (inputSize > arraySize)      //make sure no more than 40 digits where entered
		cout << "\nThe integer entered was to long.  Array not initialized." << endl;
	else
        for (int loopSize = 0; loopSize < inputSize; loopSize++)
        //subtract ASCII value for '0' to get raw value
		//store digits at end of 40 digit array all non initialized parts of array stay a 0
        bigNumber[(arraySize - 1) - loopSize] = line[(inputSize - 1) - loopSize];

		for (int digitIndex = 0; digitIndex < arraySize; digitIndex++)
			bigNumber[digitIndex] = intConvert(bigNumber[digitIndex]);

}//end input function


int HugeInteger::intConvert(char toConvert)
{
	switch(toConvert)
	{
		case '1': return 1;
		case '2': return 2;
		case '3': return 3;
		case '4': return 4;
		case '5': return 5;
		case '6': return 6;
		case '7': return 7;
		case '8': return 8;
		case '9': return 9;
		case '0': return 0;
		default: return 0;
	}
}

[Ganon11]

When inputting a number, the negative sign can only be in front of the number, right? Then all you need to do is check the first character to see if it is '-' or not. If it is '-', set some flag to indicate the hugeInteger is negative. If not, it's a number, and you proceed as normal.

[AZRebelCowgirl73]

What would I do once I set the flag: Like for example for outputing the number:

HugeInteger::HugeInteger()	//default constructor const arraySize = 40
:arraySize(40)
{
	for (int loopSize = 0; loopSize < arraySize; loopSize++)
		bigNumber[loopSize] = 0;	//initialize array with 0's
	
	isNegative = false;

}//end constructor


void HugeInteger::input()
{
    char line[41];      //characters read in to hold integer values
      
    cout << "\nEnter Huge Integer (Max: 40 digits): ";
    cin.getline(line, sizeof line);

    inputSize = strlen(line);      //determine size of users integer

	if (isdigit(line[0]))
		isNegative = true;

    if (inputSize > arraySize)      //make sure no more than 40 digits where entered
		cout << "\nThe integer entered was to long.  Array not initialized." << endl;
	else
        if (isNegative)//if number is positive
			for (int loopSize = 0; loopSize < inputSize; loopSize++)
			//subtract ASCII value for '0' to get raw value store digits at 
			//end of 40 digit array all non initialized parts of array stay a 0
			bigNumber[(arraySize - 1) - loopSize] = line[(inputSize - 1) - loopSize] - '0';
		

}//end input function

void HugeInteger::output() const
{
	bool leadingZero = true;

	//avoid printing all leading zero's
	for (int digitIndex = 0; digitIndex < arraySize; digitIndex++)
	{
		int digit = bigNumber[digitIndex];
			//if it is not a zero, print it, and set leadingZero to false;
			if (digit != 0)
			{
				leadingZero = false;
				cout << digit;
			}//end if
			else
				//else if digit is zero, print only if not leading
				if (!leadingZero)
					cout << digit;
	}//end for
     
}//end output function

[Laharl]

When converting a negative number, you'll need an extra slot in the array. That said, just set the first element to '-', then pass the address of the second element (arrayname[1]) to the function when setting it and you don't have to change any other code at all to create it.

[Ganon11]

When outputting, if the number is negative (isNegative == true), output a '-' first - otherwise, don't print anything before the digits.

The entire point of having this isNegative variable is to let you, the programmer, think of the number as in one of two possible states either it is negative (and thus you treat it one way: adding a '-' to the output, multiplying the result by -1) or not negative (and thus you treat it another way: it's a normal, positive number).

[weaknessforcats]

Er, HugeInteger has a 40 byte array for the ineger value. This is 320 bits. That is indeed a huge integer.

However, what you do is use the array at the bit level. That is, as one 320-bit integer with the left bit set when the number is negative. You would normally do this by converting the integer value as a positive value to a 2's-complement value.

The HugeInteger operator+, operator-, etc handle the bit operations.

So for a string with the value, convert to a 320-bit number and if the vlaue was negative, convert that to 2's-complement.

All of your application code works with HugeInteger and you will provide all necessary code to use numbers of this size.