public static IEnumerable <ulong> GetPrimeFactors(this ulong num, PrimeCalculator cal)
{
cal.ExtendToMinimumGT(num / 2); // so that cal.Primes is populated with all prime factors needed
if (cal.IsPrimeAutoExpand(num)) // Don't need to consider num which is a prime.
{
yield break;
}
foreach (var prime in cal.Primes)
{
while (num % prime == 0)
{
yield return(prime);
num /= prime;
}
if (num == 1)
{
break;
}
}
}
public static IEnumerable <ulong> GetDistinctPrimeFactors(this ulong num, PrimeCalculator cal)
{
return(num.GetPrimeFactors(cal).Distinct());
}