internalIsPrime method
Returns whether oddN
is prime, assuming it's an odd number. This is only
public for testing. Use the public isPrime function instead.
Implementation
bool internalIsPrime(int oddN) {
for (int i = 1;; ++i) {
final p = i < _p.length ? _p[i] : addPrime();
if (p * p > oddN) return true;
if (oddN % p == 0) return false;
}
}