Problem with return true and if statement

Question

I'm making a
ship shooter
game and I have a problem with the collision detection for the
corners of the stage. When you hold down two of the arrows to move
the ship into the corners of the screen, the ship will go past it.
The function bellow is what I'm using to detect this collision. The
reason I'm using a function is because it's used for the ship and
for all the balls from the cannons (as shown in the last two lines
of the attached code). This is the reason I need the return true,
so the if statement can be evaluated to true and then unload the
movieclip of the cannon ball. When I remove the return true, the
collision works fine, but obviously my cannon balls all get stuck
on the edges.
Any ideas?

Answer 1

Well the function is called every frame, for the ship and for
every cannon ball that's on the screen. So it could be called about
4 times or so per frame. The problem is that ship goes through the
corners of the stage (btw, the green background is the stage area)
when you go in a diagonal direction.
Just curious...what's the unnecessary code you're talking
about?