public static BigFloat FromString(String s)
{
/*
* String must be either of the format *e*f*e*
* or of the special value formats: 0NaN*e* 0nan*e* 0+oo*e* 0-oo*e*
* Where * indicates an integer value (digit)
*/
BIM sig, exp;
int sigSize, expSize;
bool isNeg;
if (s.IndexOf('f') == -1)
{
String val = s;
sigSize = int.Parse(s.Substring(4, s.IndexOf('e') - 4));
expSize = int.Parse(s.Substring(s.IndexOf('e') + 1));
if (sigSize <= 0 || expSize <= 0)
{
throw new FormatException("Significand and Exponent sizes must be greater than 0");
}
return(new BigFloat(val, sigSize, expSize));
}
sig = BIM.Parse(s.Substring(0, s.IndexOf('e')));
exp = BIM.Parse(s.Substring(s.IndexOf('e') + 1, s.IndexOf('f') - s.IndexOf('e') - 1));
sigSize = int.Parse(s.Substring(s.IndexOf('f') + 1, s.IndexOf('e', s.IndexOf('e') + 1) - s.IndexOf('f') - 1));
expSize = int.Parse(s.Substring(s.IndexOf('e', s.IndexOf('e') + 1) + 1));
isNeg = s[0] == '-'; //We do this so that -0 is parsed correctly
if (sigSize <= 0 || expSize <= 0)
{
throw new FormatException("Significand and Exponent sizes must be greater than 0");
}
sigSize = sigSize - 1; //Get rid of sign bit
sig = BIM.Abs(sig); //sig must be positive
//Uncomment if you want to shift the exponent for the user (i.e. 0e-1f24e8 --> 0e126f24e8)
//exp = exp + BIM.Pow(new BIM(2), expSize-1) - BIM.One;
if (exp < 0 || exp >= BIM.Pow(new BIM(2), expSize))
{
throw new FormatException("The given exponent " + exp + " cannot fit in the bit size " + expSize);
}
if (sig >= BIM.Pow(new BIM(2), sigSize))
{
throw new FormatException("The given significand " + sig + " cannot fit in the bit size " + (sigSize + 1));
}
return(new BigFloat(isNeg, sig, exp, sigSize, expSize));
}
public static BigFloat operator +(BigFloat x, BigFloat y)
{
Contract.Requires(x.exponentSize == y.exponentSize);
Contract.Requires(x.significandSize == y.significandSize);
if (x.value != "" || y.value != "")
{
if (x.value == "NaN" || y.value == "NaN" || x.value == "+oo" && y.value == "-oo" || x.value == "-oo" && y.value == "+oo")
{
return(new BigFloat("NaN", x.significandSize, x.exponentSize));
}
if (x.value != "")
{
return(new BigFloat(x.value, x.significandSize, x.exponentSize));
}
return(new BigFloat(y.value, y.significandSize, y.exponentSize));
}
if (x.exponent > y.exponent)
{
BigFloat temp = x;
x = y;
y = temp;
}
BIM xsig = x.significand, ysig = y.significand;
BIM xexp = x.exponent, yexp = y.exponent;
if (yexp - xexp > x.significandSize) //One of the numbers is relatively insignificant
{
return(new BigFloat(y.isSignBitSet, y.significand, y.exponent, y.significandSize, y.exponentSize));
}
BIM hiddenBitPow = BIM.Pow(2, x.significandSize - 1);
if (xexp > 0)
{
xsig += hiddenBitPow;
}
else
{
++xexp;
}
if (yexp > 0)
{
ysig += hiddenBitPow;
}
else
{
++yexp;
}
if (x.isSignBitSet)
{
xsig = -xsig;
}
if (y.isSignBitSet)
{
ysig = -ysig;
}
xsig >>= (int)(yexp - xexp); //Guaranteed to fit in a 32-bit integer
ysig += xsig;
bool isNeg = ysig < 0;
ysig = BIM.Abs(ysig);
if (ysig == 0)
{
return(new BigFloat(x.isSignBitSet && y.isSignBitSet, 0, 0, x.significandSize, x.exponentSize));
}
if (ysig >= hiddenBitPow * 2)
{
ysig >>= 1;
++yexp;
}
while (ysig < hiddenBitPow && yexp > 1)
{
ysig <<= 1;
--yexp;
}
if (ysig < hiddenBitPow)
{
yexp = 0;
}
else
{
ysig -= hiddenBitPow;
}
if (yexp >= BIM.Pow(2, x.exponentSize) - 1)
{
return(new BigFloat(y.isSignBitSet ? "-oo" : "+oo", x.significandSize, x.exponentSize));
}
return(new BigFloat(isNeg, ysig, yexp, x.significandSize, x.exponentSize));
}