internal static bool DivisibleBySomeLowPrime(Digits digits, int n)
{
if (n == 0 || (digits[0] & 1) == 0)
{
Debug.Assert(false, "untested code");
return(true);
}
for (int l = 0; l != LowPrimesProduct.Length; l++)
{
Digit product = LowPrimesProduct[l]
, productInverse = Digit.TwoAdicInverse(product)
, r = 0;
for (int i = 0; i != n; i++)
{
Digit mulby;
unchecked {
r += digits[i];
if (r < digits[i])
{
r -= product;
}
mulby = productInverse * r;
Debug.Assert(mulby * product == r, "internal error");
}
r = product - Digit2.Hi((UInt64)mulby * product);
}
if (Digit.OddGcd(r, product) != 1)
{
return(true);
}
}
return(false);
}
