static int is_primitive_root(UV n, UV r)
{
UV fac[MPU_MAX_FACTORS+1];
int i, nfacs;
/* if ( (r&1) & powmod(n, (r-1)>>1, r) == 1 ) return 0; */
nfacs = factor_exp(r-1, fac, 0);
for (i = 0; i < nfacs; i++) {
UV m = powmod(n, (r-1)/fac[i], r);
if (m == 1) return 0;
}
return (gcd_ui(n,r) == 1);
}
unsigned long binomial(unsigned long n, unsigned long k) {
unsigned long d, g, r = 1;
if (k == 0) return 1;
if (k == 1) return n;
if (k >= n) return (k == n);
if (k > n/2) k = n-k;
for (d = 1; d <= k; d++) {
if (r >= ULONG_MAX/n) { /* Possible overflow */
unsigned long nr, dr; /* reduced numerator / denominator */
g = gcd_ui(n, d); nr = n/g; dr = d/g;
g = gcd_ui(r, dr); r = r/g; dr = dr/g;
if (r >= ULONG_MAX/nr) return 0; /* Unavoidable overflow */
r *= nr;
r /= dr;
n--;
} else {
r *= n--;
r /= d;
}
}
return r;
}
