public static MultiPrecision <N> Div(MultiPrecision <N> a, long b)
{
if (a.IsNaN)
{
return(NaN);
}
if (a.IsZero)
{
if (b == 0)
{
return(NaN);
}
return((a.Sign == UIntUtil.Sign(b)) ? Zero : MinusZero);
}
if (!a.IsFinite)
{
return((a.Sign == UIntUtil.Sign(b)) ? PositiveInfinity : NegativeInfinity);
}
if (b == 0)
{
return((a.Sign == Sign.Plus) ? PositiveInfinity : NegativeInfinity);
}
if (b == 1)
{
return(a);
}
if (b == -1)
{
return(Neg(a));
}
UInt64 b_abs = UIntUtil.Abs(b);
if (UIntUtil.IsPower2(b_abs))
{
MultiPrecision <N> a_power2 = Ldexp(a, -UIntUtil.Power2(b_abs));
return(b >= 0 ? a_power2 : Neg(a_power2));
}
int expands = BigUInt <Plus4 <N> > .Length - BigUInt <N> .Length;
BigUInt <Plus4 <N> > acc = new(a.mantissa.Value.ToArray(), expands);
acc /= b_abs;
int lzc = acc.LeadingZeroCount;
acc <<= lzc;
Int64 exponent = a.Exponent - lzc;
Sign sign = (a.Sign == UIntUtil.Sign(b)) ? Sign.Plus : Sign.Minus;
bool round = acc[expands - 1] > UIntUtil.UInt32Round;
Mantissa <N> mantissa = new(acc.Value.Skip(expands).ToArray(), enable_clone : false);
return(new MultiPrecision <N>(sign, exponent, mantissa, round));
}
public static MultiPrecision <N> Sub(MultiPrecision <N> a, long b)
{
if (b == 0)
{
return(a);
}
if (a.IsNaN)
{
return(NaN);
}
if (a.IsZero)
{
return(Neg(b));
}
if (!a.IsFinite)
{
return(a);
}
UInt64 b_abs = UIntUtil.Abs(b);
if (a.Sign == UIntUtil.Sign(b))
{
(Mantissa <N> n, Int64 exponent, bool round, Sign sign) = Diff(a.mantissa, b_abs, -a.Exponent);
return(new MultiPrecision <N>(
(a.Sign == Sign.Plus ^ sign == Sign.Plus) ? Sign.Minus : Sign.Plus,
exponent + a.Exponent, n, round));
}
else
{
(Mantissa <N> n, Int64 exponent, bool round) = Add(a.mantissa, b_abs, -a.Exponent);
return(new MultiPrecision <N>(a.Sign, exponent + a.Exponent, n, round));
}
}