private static MultiPrecision <N> BesselKNearZero(MultiPrecision <N> nu, MultiPrecision <N> z)
{
int n = (int)Round(nu);
if (nu != n)
{
MultiPrecision <N> dnu = nu - n;
if (dnu.Exponent >= -96)
{
return(MultiPrecision <Plus4 <N> > .BesselKNonIntegerNu(nu.Convert <Plus4 <N> >(), z.Convert <Plus4 <N> >()).Convert <N>());
}
if (dnu.Exponent >= -272)
{
return(MultiPrecision <Plus8 <N> > .BesselKNonIntegerNu(nu.Convert <Plus8 <N> >(), z.Convert <Plus8 <N> >()).Convert <N>());
}
throw new ArgumentException(
"The calculation of the BesselK function value is invalid because it loses digits" +
" when nu is extremely close to an integer. (|nu - round(nu)| < 1.32 x 10^-82 and nu != round(nu))",
nameof(nu));
}
return(MultiPrecision <Plus4 <N> > .BesselKIntegerNuNearZero(n, z.Convert <Plus4 <N> >()).Convert <N>());
}
