FastPrime.csx

bool IsPrime(int input)
{
	//2 and 3 are primes
	if (input == 2 || input == 3)
		return true;
	else if (input % 2 == 0 || input % 3 == 0)
		return false;     //Is divisible by 2 or 3?
	else
	{
		for (int i = 5; i * i <= input; i += 6)
		{
			if (input % i == 0 || input % (i + 2) == 0)
				return false;
		}
		return true;
	}
}

bool IsPrime2(int candidate) 
{
	if ( candidate % 2 <= 0 ) 
	{
		return candidate == 2;
	}
	int power2 = 9;
	for ( int divisor = 3; power2 <= candidate; divisor += 2 ) 
	{
		if ( candidate % divisor == 0 )
		return false;
		power2 += divisor * 4 + 4;
	}
	return true;
}