buildwall.lua

local slot_switch
slot_switch = function()
  if turtle.getSelectedSlot() == 16 then
    return turtle.select(1)
  else
    return turtle.select(turtle.getSelectedSlot() + 1)
  end
end
local slot_check
slot_check = function()
  if turtle.getItemCount() == 0 then
    print("Slot empty, switching...")
  end
  while turtle.getItemCount() == 0 do
    slot_switch()
  end
end
local lay_blocks
lay_blocks = function()
  if turtle.detect() then
    slot_check()
    turtle.placeDown()
    turtle.up()
    turtle.turnLeft()
    return turtle.turnLeft()
  else
    slot_check()
    turtle.placeDown()
    return turtle.forward()
  end
end
local running = true
print("Running...")
if turtle.detect() then
  print("Wrong direction, turning around...")
  turtle.turnLeft()
  turtle.turnLeft()
end
print("Building wall now!")
while running do
  if turtle.detectUp() then
    slot_check()
    turtle.placeDown()
    local last_row = true
    while last_row do
      lay_blocks()
      if turtle.detectUp() then
        turtle.placeDown()
        last_row = false
        running = false
      end
    end
  else
    lay_blocks()
  end
end
return print("All done!")