Variable isn't doubling [easy]

My code just prints 1 over and over as the variable, when it should be doing 1 then 2, then 4, then 8,16,32,64,128, then back to 1,2,4,8,16 and so forth, over and over, but my "debug" style thing that prints the variable is just saying 1 and 1 and 1 when it should be 1,2,4,8,16,32,64,128 :/ It should be easy, thanks!
Here's my code;

local side = "back"
local num = 1

function s()
sleep(.2)
end

function glow()
if num < 128 then
local num = num + num
end

if num == 128 then
local num = 1
end

rs.setBundledOutput( side, num)
end

while true do
print(num)
s()
glow()
end

just take out the local when you double it or that change only reflects in the function in which you double it

Ohhh! I didn't realise that.
Thank you so much! I was so used to using local in defining variables, thank you so much.

You can do the doubling up to 128 simply by replacing:

if num < 128 then
  num = num + num
end
if num == 128 then
  num = 1
end

with:

num=(num*2)%256

EDIT: just noticed that you wan't it to start at zero, so this might need some modification :(/>/>
EDIT: just thought of this trick:

num = math.max(1, (num*2)%256)

And then you step back and realize that you've just made the whole thing harder to read for no actual gain, and made it less efficient too.

Fatal_Exception, on 05 October 2012 - 11:48 PM said:

And then you step back and realize that you've just made the whole thing harder to read for no actual gain, and made it less efficient too.

I like short code, but if you want efficiency, use shift operators. >.< without the math.max, it's definitely more efficient. It's just unfortunate he doesn't want zero.
And if you go further on efficiency, 'num=num+num' requires more operations than 'num=num*2'. And that requires more operations than 'bit.blshift(num,2)'.
I was just trying to help there. If bloodless wants a hint that's more on the same road; you can use 'if … else … end' to make it more efficient/coherent.