ComputerCraft Turtle Rectangle

local tArgs = { ... }
if #tArgs ~= 1 then
  error( "Usage: rectangle <length> <width>" )
  return
end

length = tArgs[1]
width = tArgs[2]
slot = 1
turtle.select(slot)

turtle.forward()

for i=1,width do
    for j=1,length do
        turtle.placeDown()
        turtle.forward()
        if turtle.getItemCount(slot) == 0 then
            slot = slot + 1
            turtle.select(slot)
        end
    end
    for k=1,length do
        turtle.back()
    end
    turtle.turnRight()
    turtle.forward()
    turtle.turnLeft()
end