public static bool AreEqualExactUnums(Unum left, Unum right) => left.IsZero() && right.IsZero() ? true : left.UnumBits == right.UnumBits;
public static Unum SubtractExactUnums(Unum left, Unum right) => AddExactUnums(left, NegateExactUnum(right));
public static Unum NegateExactUnum(Unum input) => input.Negate();
public static Unum AddExactUnums(Unum left, Unum right)
{
// It could be only FractionSizeMax + 2 long if that would be Hastlayer-compatible (it isn't due to static
// array sizes).
var scratchPad = new BitMask(left._environment.Size);
// Handling special cases first.
if (left.IsNan() || right.IsNan())
{
return(new Unum(left._environment, left.QuietNotANumber));
}
if ((left.IsPositiveInfinity() && right.IsNegativeInfinity()) ||
(left.IsNegativeInfinity() && right.IsPositiveInfinity()))
{
return(new Unum(left._environment, left.QuietNotANumber));
}
if (left.IsPositiveInfinity() || right.IsPositiveInfinity())
{
return(new Unum(left._environment, left.PositiveInfinity));
}
if (left.IsNegativeInfinity() || right.IsNegativeInfinity())
{
return(new Unum(left._environment, left.NegativeInfinity));
}
var exponentValueDifference = left.ExponentValueWithBias() - right.ExponentValueWithBias();
var signBitsMatch = left.IsPositive() == right.IsPositive();
var resultSignBit = false;
var biggerBitsMovedToLeft = 0;
var smallerBitsMovedToLeft = 0;
var resultExponentValue = 0;
if (exponentValueDifference == 0) // Exponents are equal.
{
resultExponentValue = left.ExponentValueWithBias();
// We align the fractions so their Most Significant Bit gets to the leftmost position that the
// FractionSize allows. This way the digits that won't fit automatically get lost.
biggerBitsMovedToLeft = left.FractionSizeMax + 1 - (left.FractionSize() + 1);
smallerBitsMovedToLeft = left.FractionSizeMax + 1 - (right.FractionSize() + 1);
// Adding the aligned Fractions.
scratchPad = AddAlignedFractions(
left.FractionWithHiddenBit() << biggerBitsMovedToLeft,
right.FractionWithHiddenBit() << smallerBitsMovedToLeft,
signBitsMatch);
if (!signBitsMatch)
{
// If the value of the Hidden Bits match we just compare the fractions,
// and get the Sign of the bigger one.
if (left.HiddenBitIsOne() == right.HiddenBitIsOne())
{
resultSignBit = left.Fraction() >= right.Fraction()
? !left.IsPositive() // Left Fraction is bigger.
: !right.IsPositive(); // Right Fraction is bigger.
}
// Otherwise we get the Sign of the number that has a Hidden Bit set.
else
{
resultSignBit = left.HiddenBitIsOne() ? !left.IsPositive() : !right.IsPositive();
}
}
else
{
resultSignBit = !left.IsPositive();
}
}
else if (exponentValueDifference > 0) // Left Exponent is bigger.
{
// We align the fractions according to their exponent values so the Most Significant Bit of the bigger
// number gets to the leftmost position that the FractionSize allows.
// This way the digits that won't fit automatically get lost.
resultSignBit = !left.IsPositive();
resultExponentValue = left.ExponentValueWithBias();
biggerBitsMovedToLeft = left.FractionSizeMax + 1 - (left.FractionSize() + 1);
smallerBitsMovedToLeft = left.FractionSizeMax + 1 - (right.FractionSize() + 1) - exponentValueDifference;
scratchPad = left.FractionWithHiddenBit() << biggerBitsMovedToLeft;
// Adding the aligned Fractions.
scratchPad = AddAlignedFractions(scratchPad,
right.FractionWithHiddenBit() << smallerBitsMovedToLeft, signBitsMatch);
}
else // Right Exponent is bigger.
{
// We align the fractions according to their exponent values so the Most Significant Bit of the bigger
// number gets to the leftmost position that the FractionSize allows.
// This way the digits that won't fit automatically get lost.
resultSignBit = !right.IsPositive();
resultExponentValue = right.ExponentValueWithBias();
biggerBitsMovedToLeft = left.FractionSizeMax + 1 - (right.FractionSize() + 1);
smallerBitsMovedToLeft = left.FractionSizeMax + 1 - (left.FractionSize() + 1) + exponentValueDifference;
scratchPad = right.FractionWithHiddenBit() << biggerBitsMovedToLeft;
// Adding the aligned Fractions.
scratchPad = AddAlignedFractions(scratchPad,
left.FractionWithHiddenBit() << smallerBitsMovedToLeft, signBitsMatch);
}
// Calculating how the addition changed the exponent of the result.
var exponentChange = scratchPad.GetMostSignificantOnePosition() - (left.FractionSizeMax + 1);
var resultExponent = new BitMask(left._environment.Size) +
ExponentValueToExponentBits(resultExponentValue + exponentChange, left.Size);
// Calculating the ExponentSize needed to the excess-k notation of the results Exponent value.
var resultExponentSize = (byte)(ExponentValueToExponentSize(resultExponentValue + exponentChange) - 1);
var resultUbit = false;
if (smallerBitsMovedToLeft < 0)
{
resultUbit = true; // There are lost digits, so we set the ubit to 1.
}
// If there are no lost digits, we can shift out the least significant zeros to save space.
else
{
scratchPad = scratchPad.ShiftOutLeastSignificantZeros();
}
ushort resultFractionSize = 0;
//Calculating the results FractionSize.
if (scratchPad.GetMostSignificantOnePosition() == 0) // If the Fraction is zero, so is the FractionSize.
{
resultExponent = scratchPad; // 0
resultExponentSize = 0; // If the Fraction is zero, so is the ExponentSize.
}
else
{
resultFractionSize = (ushort)(scratchPad.GetMostSignificantOnePosition() - 1);
}
if (resultExponent.GetMostSignificantOnePosition() != 0) // Erase the hidden bit if it is set.
{
scratchPad = scratchPad.SetZero((ushort)(scratchPad.GetMostSignificantOnePosition() - 1));
resultFractionSize = (ushort)(resultFractionSize == 0 ? 0 : resultFractionSize - 1);
}
// This is temporary, for the imitation of float behaviour. Now the Ubit works as a flag for rounded values.
// When Ubounds will be implemented this should be handled in the addition operator.
if ((!left.IsExact()) || (!right.IsExact()))
{
resultUbit = true;
}
// Setting the parts of the result Unum to the calculated values.
var resultBitMask = left.AssembleUnumBits(resultSignBit, resultExponent, scratchPad,
resultUbit, resultExponentSize, resultFractionSize);
return(new Unum(left._environment, resultBitMask));
}
