Those two functions are used to update the positions due to the effects of gravity, and "wrap" the star's position if it goes off screen. I was wondering though, when dereferencing the iterator, it returns by value right? So it actually would be faster if I modified the functions to accept iterators as parameters, rather than references to the object itself. Because the way I see it, even though I'm passing a reference to the function, by dereferencing the iterator I'm losing a whole lot of time since it has to return a copy of the value...no?