/// <summary>
/// Returns a base-10 string representing the number.
///
/// Note: This is inefficient and possibly inaccurate. Please use with enough
/// rounding digits (set using the RoundingDigits property) to ensure accuracy
/// </summary>
public override string ToString()
{
if (IsSpecialValue)
{
SpecialValueType s = SpecialValue;
if (s == SpecialValueType.ZERO)
{
return String.Format("0{0}0", System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator);
}
else if (s == SpecialValueType.INF_PLUS)
{
return System.Globalization.CultureInfo.CurrentCulture.NumberFormat.PositiveInfinitySymbol;
}
else if (s == SpecialValueType.INF_MINUS)
{
return System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NegativeInfinitySymbol;
}
else if (s == SpecialValueType.NAN)
{
return System.Globalization.CultureInfo.CurrentCulture.NumberFormat.NaNSymbol;
}
else
{
return "Unrecognised special type";
}
}
if (scratch.Precision.NumBits != mantissa.Precision.NumBits)
{
scratch = new BigInt(mantissa.Precision);
}
//The mantissa expresses 1.xxxxxxxxxxx
//The highest possible value for the mantissa without the implicit 1. is 0.9999999...
scratch.Assign(mantissa);
//scratch.Round(3);
scratch.Sign = false;
BigInt denom = new BigInt("0", mantissa.Precision);
denom.SetBit(mantissa.Precision.NumBits - 1);
bool useExponentialNotation = false;
int halfBits = mantissa.Precision.NumBits / 2;
if (halfBits > 60) halfBits = 60;
int precDec = 10;
if (exponent > 0)
{
if (exponent < halfBits)
{
denom.RSH(exponent);
}
else
{
useExponentialNotation = true;
}
}
else if (exponent < 0)
{
int shift = -(exponent);
if (shift < precDec)
{
scratch.RSH(shift);
}
else
{
useExponentialNotation = true;
}
}
string output;
if (useExponentialNotation)
{
int absExponent = exponent;
if (absExponent < 0) absExponent = -absExponent;
int powerOf10 = (int)((double)absExponent * Math.Log10(2.0));
//Use 1 extra digit of precision (this is actually 32 bits more, nb)
BigFloat thisFloat = new BigFloat(this, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
thisFloat.mantissa.Sign = false;
//Multiplicative correction factor to bring number into range.
BigFloat one = new BigFloat(1, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
BigFloat ten = new BigFloat(10, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
BigFloat tenRCP = ten.Reciprocal();
//Accumulator for the power of 10 calculation.
BigFloat acc = new BigFloat(1, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
BigFloat tenToUse;
if (exponent > 0)
{
tenToUse = new BigFloat(tenRCP, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
}
else
{
tenToUse = new BigFloat(ten, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
}
BigFloat tenToPower = new BigFloat(1, new PrecisionSpec(mantissa.Precision.NumBits + 1, PrecisionSpec.BaseType.BIN));
int powerTemp = powerOf10;
//Fast power function
while (powerTemp != 0)
{
tenToPower.Mul(tenToUse);
tenToUse.Assign(tenToPower);
if ((powerTemp & 1) != 0)
{
acc.Mul(tenToPower);
}
powerTemp >>= 1;
}
thisFloat.Mul(acc);
//If we are out of range, correct.
if (thisFloat.GreaterThan(ten))
{
thisFloat.Mul(tenRCP);
if (exponent > 0)
{
powerOf10++;
}
else
{
powerOf10--;
}
}
else if (thisFloat.LessThan(one))
{
thisFloat.Mul(ten);
if (exponent > 0)
{
powerOf10--;
}
else
{
powerOf10++;
}
}
//Restore the precision and the sign.
BigFloat printable = new BigFloat(thisFloat, mantissa.Precision);
printable.mantissa.Sign = mantissa.Sign;
output = printable.ToString();
if (exponent < 0) powerOf10 = -powerOf10;
output = String.Format("{0}E{1}", output, powerOf10);
}
else
{
BigInt bigDigit = BigInt.Div(scratch, denom);
bigDigit.Sign = false;
scratch.Sub(BigInt.Mul(denom, bigDigit));
if (mantissa.Sign)
{
output = String.Format("-{0}.", bigDigit);
}
else
{
output = String.Format("{0}.", bigDigit);
}
denom = BigInt.Div(denom, 10u);
while (!denom.IsZero())
{
uint digit = (uint)BigInt.Div(scratch, denom);
if (digit == 10) digit--;
scratch.Sub(BigInt.Mul(denom, digit));
output = String.Format("{0}{1}", output, digit);
denom = BigInt.Div(denom, 10u);
}
output = RoundString(output, RoundingDigits);
}
return output;
}
/// <summary>
/// Tests whether n1 is greater than n2
/// </summary>
public static bool GreaterThan(BigFloat n1, BigFloat n2)
{
return n1.GreaterThan(n2);
}