public static Rational MakeNarrow(Rational r, Rational b)
{
if (r.GetHighPrimeIndex() == b.GetHighPrimeIndex())
{
return(r); // can't narrow on same prime level
}
double r_ = r.ToDouble();
double b_ = b.ToDouble();
double l = Math.Log(r_, b_); // e.g. 1.58 for {3, 2}
Pow e = (Pow)(l + 0.25); // something between Floor and Round
r /= b.Power(e);
return(r);
}
public static Rational MakeNarrow(Rational r, int basePrimeIndex)
{
if (r.GetHighPrimeIndex() <= basePrimeIndex)
{
return(r); // can't narrow
}
r = ValidateNarrow(r);
//
double rr = r.ToDouble();
if (rr < 1.0)
{
return(r); // e.g. for 5/6 - doubtful !!!
}
int b = Utils.GetPrime(basePrimeIndex); // base prime: 2, 3,..
double l = Math.Log(rr - 1.0, b);
Pow e = (Pow)Math.Round(l);
Long d = Utils.Pow(b, e);
r /= d;
return(r);
}