Turtle Program only goes to the second slot when out of blocks, doesn't switch to third and so on

I made a turtle program to make a platform levels for my "factory" in Feed-The-Beast. Every time it runs out of blocks in a slot, I wanted it to switch to the next slot, but it only switches from the first slot to the second slot. How can I fix this?

--[[ VARIABLES ]]--

--[[ FUNCTIONS ]]--

function woodSlot()
a = 1
local b = turtle.getItemCount(a)
if b == 0 then
  a = a+1
  turtle.select(a)
end
end

--[[ MAIN CODE ]]--
while true do
if turtle.back() == true then
  turtle.place()
elseif turtle.back() == false then
  turtle.turnRight()
end
woodSlot()
end

every time you run the woodSlut function you reset the value to 1, define a = 1 in the "–[[ VARIABLES ]]–" !

move a = 1 out of the woodSlot() function, it keeps resetting to 1 and then if the amount in slot a is 0 it increases it but then resets back to 1

--[[ VARIABLES ]]--

--[[ FUNCTIONS ]]--
a = 1
function woodSlot()

local b = turtle.getItemCount(a)
if b == 0 then
  a = a+1
  turtle.select(a)
end
end

--[[ MAIN CODE ]]--
while true do
if turtle.back() == true then
  turtle.place()
elseif turtle.back() == false then
  turtle.turnRight()
end
woodSlot()
end

remiX, on 05 January 2013 - 07:54 AM said:

move a = 1 out of the woodSlot() function, it keeps resetting to 1 and then if the amount in slot a is 0 it increases it but then resets back to 1

--[[ VARIABLES ]]--

--[[ FUNCTIONS ]]--
a = 1
function woodSlot()

local b = turtle.getItemCount(a)
if b == 0 then
  a = a+1
  turtle.select(a)
end
end

--[[ MAIN CODE ]]--
while true do
if turtle.back() == true then
  turtle.place()
elseif turtle.back() == false then
  turtle.turnRight()
end
woodSlot()
end

Well that was stupid of me! Thanks!