PointRef PointCreateInvert(PointRef p, CurveRef curve)
{
if (PointIsTeta(p))
return PointCreateTeta();
PointRef q = PointCopy(p);
// P = (xp, yp)
// -P = (xp, - yp - a1.xp - a3)
mpz_t mon;
// mon = a1.xp
mpz_init_set(mon, curve->a[1]);
mpz_mul(mon, mon, q->x);
mpz_mod(mon, mon, curve->mod);
// yp = -yp
mpz_neg(q->y, q->y);
mpz_mod(q->y, q->y, curve->mod);
// yp = -yp - a1.xp
mpz_sub(q->y, q->y, mon);
mpz_mod(q->y, q->y, curve->mod);
// yp = -yp - a1.xp - a3
mpz_sub(q->y, q->y, curve->a[3]);
mpz_mod(q->y, q->y, curve->mod);
mpz_clear(mon);
return q;
}
void test_point() {
int ndim = 5;
int i;
double diff;
int retval = 0;
printf("\nTesting points\n");
struct Point* p1 = PointAlloc(ndim);
struct Point* p2 = PointAlloc(ndim);
struct Point* p3;
for (i=0; i<p1->x->size; i++) {
p1->x->data[i] = (double) i;
p2->x->data[i] = (double) 2*i;
printf("p1->x->data[%d]: %lf\n", i, p1->x->data[i]);
printf("p2->x->data[%d]: %lf\n", i, p2->x->data[i]);
}
if (PointEqual(p1,p2)) {
printf("Points are equal\n");
} else {
printf("Points differ\n");
}
diff = PointDist(p1,p2);
if (diff < 0.0) {
retval = 1;
} else {
printf("diff: %lf\n", diff);
}
printf("copying Points\n");
PointCopy(p2,p1);
if (PointEqual(p1,p2)) {
printf("Points are equal\n");
} else {
printf("Points differ\n");
}
// this would fail
//PointEqual(p1,p3);
PointFree(p1);
PointFree(p2);
}
