Wall (Blockly Lua)

-- Blockly source: http://blockly-lua.appspot.com/static/apps/code/index.html#w5yeux

function create_wall(instructions)
  for _, row in ipairs(instructions) do
    for _, slot_number in ipairs(row) do
      if not turtle.select(slot_number) then
        return 'Unable to select slot #' .. slot_number
      end
      if not turtle.place() then
        return 'Unable to place item from slot #' .. slot_number
      end
      turtle.turnRight()
      if not turtle.forward() then
        return 'Unable to move forward.'
      end
      turtle.turnLeft()
    end
    turtle.turnRight()
    for count = 1, math.floor(#row) do
      if not turtle.back() then
        return 'Unable to move backward.'
      end
    end
    turtle.turnLeft()
    if not turtle.up() then
      return 'Unable to move up.'
    end
  end
  for count2 = 1, math.floor(#instructions) do
    if not turtle.down() then
      return 'Unable to move backward.'
    end
  end
  return 'Done.'
end


print(create_wall(({({1, 2, 1, 2, 1}), ({2, 1, 2, 1, 2})})))