Neo's revised tunnel

tArgs = { ... }
todo = tonumber(tArgs[1])
--

turtle.select(1)

function refill()
  if turtle.getItemCount(1) == 0 then
  turtle.select(2)
  turtle.turnRight()
  turtle.turnRight()
  turtle.place()
  turtle.select(1)
  turtle.suck()
  turtle.dig()
  turtle.turnRight()
  turtle.turnRight()
  end
end

function checkwallLU()
refill()
turtle.turnLeft()
turtle.place()
turtle.down()
turtle.place()
turtle.up()
turtle.turnRight()
os.sleep(0.1)
end

function checkwallU()
refill()
turtle.turnRight()
turtle.place()
turtle.placeUp()
end

function checkwallD()
refill()
turtle.place()
turtle.placeDown()
turtle.turnLeft()
end

for i = 1, todo do
turtle.select(1)
refill()
turtle.dig()
turtle.forward()
checkwallU()
turtle.digDown()
turtle.down()
checkwallD()
turtle.up()
checkwallLU()
end