public VeryLong Subtract(VeryLong subtrahend)
{
int minuendDecimalPlaces = GetDecimalPlaces();
int subtrahendDecimalPlaces = subtrahend.GetDecimalPlaces();
int decimalPlaces = Math.Max(minuendDecimalPlaces, subtrahendDecimalPlaces);
FillUpDecimalPlacesWithZero(decimalPlaces);
subtrahend.FillUpDecimalPlacesWithZero(decimalPlaces);
string result = "";
int diff = 0;
int borrow = 0;
int currentLastDigit = 0;
int currentLastDigitSubtrahend = 0;
int i = 0;
if (!IsLargerOrEqual(subtrahend))
{
// swap: minuend is smaller than subtrahend --> result is negative
VeryLong newMinuend = subtrahend;
VeryLong newSubtrahend = new VeryLong(ToString());
VeryLong difference = newMinuend.Subtract(newSubtrahend);
return(new VeryLong("-" + difference.ToString()));
}
while (Length() > i || subtrahend.Length() > i || borrow != 0)
{
if (GetLastDigit(i) == ".")
{
result = result.Insert(0, ".");
i++;
continue;
}
currentLastDigit = int.Parse(GetLastDigit(i));
currentLastDigitSubtrahend = int.Parse(subtrahend.GetLastDigit(i));
diff = currentLastDigit - currentLastDigitSubtrahend - borrow;
if (diff < 0)
{
borrow = 1;
diff += 10;
}
else
{
borrow = 0;
}
result = result.Insert(0, diff.ToString());
i++;
}
result = RemoveLeadingZeros(result);
return(new VeryLong(result));
}
public VeryLong Add(VeryLong other)
{
int summand1DecimalPlaces = GetDecimalPlaces();
int summand2DecimalPlaces = other.GetDecimalPlaces();
int decimalPlaces = Math.Max(summand1DecimalPlaces, summand2DecimalPlaces);
FillUpDecimalPlacesWithZero(decimalPlaces);
other.FillUpDecimalPlacesWithZero(decimalPlaces);
string result = "";
int sum = 0;
int behalte = 0;
int resultDigit = 0;
int currentLastDigit = 0;
int currentLastDigitOther = 0;
int i = 0;
while (Length() > i || other.Length() > i || behalte != 0)
{
if (GetLastDigit(i) == ".")
{
result = result.Insert(0, ".");
i++;
continue;
}
currentLastDigit = int.Parse(GetLastDigit(i));
currentLastDigitOther = int.Parse(other.GetLastDigit(i));
sum = currentLastDigit + currentLastDigitOther + behalte;
behalte = sum / 10;
resultDigit = sum % 10;
result = result.Insert(0, resultDigit.ToString());
i++;
}
return(new VeryLong(result));
}
