int equalPotential(const Potential* p1, const Potential* p2)
{
    return equalSpherical(&p1->sphere[0], &p2->sphere[0])
        && equalDisk(&p1->disk, &p2->disk)
        && equalHalo(&p1->halo, &p2->halo);
}
static int eqSpherical(lua_State* luaSt)
{
    lua_pushboolean(luaSt, equalSpherical(checkSpherical(luaSt, 1), checkSpherical(luaSt, 2)));
    return 1;
}