View difference between Paste ID: nVX9j9QG and nkeWwirf

 --[[
  Expected slot assignment/content
 
  Slot 1: 64 Torches
  Slot 2: 1 Cobble (reserved for cobble compare)
  Slot 3: Enderchest
 --]]
 
 --Variables
 
 local torchSlot = 1						-- Inventory slot of torches
 local cobbleSlot = 2	                -- Inventory slot of atleast one cobble
 local enderChestSlot = 3			    -- Inventory slot of enderchest to be used for offloading
 local frequencyOfCobbleRemoval = 30     -- Remove cobble every n blocks mined
 local doProcessContent = false
 local depth = 0
 local collected = 0
 
 -- Parameters
 
 local tArgs = { ... }
 if #tArgs < 2 then
 	print( "Usage: Area <length> <width> [Process]" )
 	print( "======================================" )
 	print( "Process If true, content -> Enderchest")
 	print( "")
 	print( "Expected content in inventory of turtle:" )
 	print( "Slot 1: Torches" )
 	print( "Slot 2: Cobble (at least 1)")
 	print( "Slot 3: Enderchest (only if Process=true)")
 	return
 end
 
 local length = tonumber( tArgs[1] )
 if length < 1 then
 	print( "Area length must be 1+" )
 	return
 end
 
 local width = 1
 
 if #tArgs > 1 then
     width = tonumber( tArgs[2] )
     if width < 1 then
 		print( "Area width must be 1+" )
 		return
 	end
 	if #tArgs > 2 then
 		doProcessContent = tArgs[3]:lower()=="true"
 	end
 end
 
 local function checkSlot(slotNr,description)
    if turtle.getItemCount(slotNr)==0 then
       print("Expected item '"..description.."' in slot "..slotNr..".")
 	  return false
    end
    return true
 end
 
 -- Check slots
 
 if not checkSlot(torchSlot,"torches") then return end
 if not checkSlot(cobbleSlot,"cobbleStone (atleast 1)") then return end
 if doProcessContent then
    if not checkSlot(enderChestSlot,"enderChest") then return end
 end
 
 -- Code
 
 local function collect()
 
 	collected = collected + 1
 	if math.fmod(collected, 25) == 0 then
 		print( "Mined "..collected.." items." )
 	end
 end
 local function refuel()
 	local fuelLevel = turtle.getFuelLevel()
 	if fuelLevel == "unlimited" or fuelLevel > 0 then
 		return
 	end
 
 	local function tryRefuel()
 		for n=1,16 do
 			if turtle.getItemCount(n) > 0 then
 				turtle.select(n)
 				if turtle.refuel(1) then
 					turtle.select(1)
 					return true
 				end
 			end
 		end
 		turtle.select(1)
 		return false
 	end
 
 	if not tryRefuel() then
 		print( "Add more fuel to continue." )
 		while not tryRefuel() do
 			sleep(1)
 		end
 		print( "Resuming Tunnel." )
 	end
 end
 local function tryDig()
 	while turtle.detect() do
 		if turtle.dig() then
 			collect()
 			sleep(0.5)
 		else
 			return false
 		end
 	end
 	return true
 end
 local function tryDigUp()
 	while turtle.detectUp() do
 		if turtle.digUp() then
 			collect()
 			sleep(0.5)
 		else
 			return false
 		end
 	end
 	return true
 end
 local function tryDigDown()
  while turtle.detectDown() do
   if turtle.digDown() then
     collect()
     sleep(0.5)
  else
    return false
   end
  end
  return true
 end
 local function tryUp()
 	refuel()
 	while not turtle.up() do
 		if turtle.detectUp() then
 			if not tryDigUp() then
 				return false
 			end
 		elseif turtle.attackUp() then
 			collect()
 		else
 			sleep( 0.5 )
 		end
 	end
 	return true
 end
 local function tryDown()
 	refuel()
 	while not turtle.down() do
 		if turtle.detectDown() then
 			if not tryDigDown() then
 				return false
 			end
 		elseif turtle.attackDown() then
 			collect()
 		else
 			sleep( 0.5 )
 		end
 	end
 	return true
 end
 local function tryForward()
 
 	refuel()
 	while not turtle.forward() do
 		if turtle.detect() then
 			if not tryDig() then
 				return false
 			end
 		elseif turtle.attack() then
 			collect()
 		else
 			sleep( 0.5 )
 		end
 	end
 	return true
 end
 
 local function dropCobbleWhenNecessary(x)
 	if math.fmod(collected,frequencyOfCobbleRemoval)==0 then
 		for n=3,16 do
 			turtle.select(n)
 			if turtle.compareTo(cobbleSlot) then
 				turtle.drop()
 			end
 		end
 	end
 end
 local function placeTorchWhenNecessary(x,y)
 	if math.fmod(x,8)==1 and math.fmod(y,8)==1 then
 		turtle.select(1)
 		if (turtle.getItemCount(torchSlot)==0) then
 			print("Out of torches, please resupply!")
 			return false
 		else
 			turtle.placeDown()
 		end
 	end
 	return true
 end
 local function processContent()
     if not doProcessContent then
 	   return
 	end
 
 	if (turtle.getItemCount(torchSlot)==0) then
 		print("No enderchest found Out of torches, please resupply!")
 		return false
 	end
 
     -- place chest
 	turtle.select(enderChestSlot)
 	turtle.placeDown()
 	--
 	print("1")
 	for slot=3,16 do
 	print("2:"..slot)
-	   	turtle.select(n)
+	   	turtle.select(slot)
 		print("3")
 		if turtle.compareTo(cobbleSlot) then
 		print("4a")
 			turtle.drop()
 		else
 		print("4b")
 			turtle.dropDown()
 		end
 		print("5")
 	end
 	print("6")
 	--retrieve chest
 	turtle.select(enderChestSlot)
 	print("7")
 	turtle.digDown()
 	print("8")
 end
 
 local function mine()
 	print( "Tunneling..." )
 	local rotation=0
 	for m=1,width do
 		for n=1,length-1 do
 			tryDigUp()
 			tryDigDown()
 			dropCobbleWhenNecessary(n)
 			placeTorchWhenNecessary(n,m)
 			tryDig()
 			if not tryForward() then
 				return false
 			end
 		end
 		tryDigUp()
 		tryDigDown()
 		if m < width then
 			if rotation==0 then
 				turtle.turnRight()
 			else
 				turtle.turnLeft()
 			end
 			tryDig()
 			if not tryForward() then
 				return false
 			end
 			if rotation==0 then
 				turtle.turnRight()
 			else
 				turtle.turnLeft()
 			end
 			rotation = 1 - rotation
 		end
 	end
 	processContent()
 end
 
 if mine() then
 	print( "Tunnel complete." )
 else
 	print( "Tunnel aborted prematurely.")
 end
 print( "Mined "..collected.." blocks total." )