You cannot divide arrays by 2

I understand what you meant, but to be really pedantic ... I think you can divide them by two, but you can't assign it back... $x = @a/2 fine, @x = 2 not so much... and that's what @a /= 2 is doing, but it's doing it to a protected value, which is the size of the array.

UPDATE: I understand that it's not what he wants and that your answer is essentially correct. I was correcting the very small pedantic point that you can divide an array by 2, you just can't set its size to 2 with @a/=2. I definitely wasn't clear on what I meant either though. @x=2 is fine, but it's really @x=(2). You can't actually express what @a/=2 is assigning, which is @a.size = @a/2. Looks like ruby or something -- you could express it with splice, but you'd have to (at least implicitly) mention the start and end of your size reduction.