static void fp_neg(element_ptr n, element_ptr a) {
if (fp_is0(a)) {
fp_set0(n);
} else {
fp_field_data_ptr p = a->field->data;
mpn_sub_n(n->data, p->primelimbs, a->data, p->limbs);
}
}
static int fp_sgn_even(element_ptr a) {
fp_field_data_ptr p = a->field->data;
if (fp_is0(a)) return 0;
mp_limb_t *sum = _alloca(p->limbs * sizeof(mp_limb_t));
int carry = mpn_add_n(sum, a->data, a->data, p->limbs);
if (carry) return 1;
return mpn_cmp(sum, p->primelimbs, p->limbs);
}
static int fp_is_sqr(element_ptr a) {
int res;
mpz_t z;
mpz_init(z);
//0 is a square
if (fp_is0(a)) return 1;
fp_to_mpz(z, a);
res = mpz_legendre(z, a->field->order) == 1;
mpz_clear(z);
return res;
}
static int fp_sgn_odd(element_ptr a) {
if (fp_is0(a)) return 0;
mp_limb_t *lp = a->data;
return lp[0] & 1 ? 1 : -1;
}
