v2

numitems = 9
squaresize = 16

function isWoodAbove()
 for i=1,numitems do
  turtle.select(i)
  if turtle.compareUp() then
   return true
  end
 end
 return false
end

function isWoodInFront()
  for i=1,numitems do
  turtle.select(i)
  if turtle.compare() then
   return true
  end
 end
 return false
end

function killTree()
 print("killtree starting")
 up = 0
 turtle.dig()
 turtle.forward()
 for i=1,math.huge() do
  if turtle.detectUp() and isWoodAbove() then
   turtle.digUp()
   turtle.up()
   up=up+1
  else
   for i=1,up do
    turtle.down()
   end
   up=0
   break
  end
 end
 print("killtree ending")
end

function moveForward()

 while not turtle.detectDown() do
  turtle.down()
	for i=1,numitems do
	 turtle.select(i)
	 if turtle.compareDown() then
	  turtle.digDown()
   end
	end
 end

 if turtle.detect() then
  if isWoodInFront() then
	 killTree()
  else
	 while turtle.detect() do
	  turtle.up()
		if isWoodAbove() then
		 turtle.digUp()
		end
   end
	end
 end
 turtle.forward()
end

--starts here
print("starting")
turnR = true
turtle.dig()
turtle.forward()


for i=1,squaresize do
 for i=1,squaresize do
	moveForward()
 end

 if turnR then
  turtle.turnRight()
  moveForward()
  turtle.turnRight()
 else
  turtle.turnLeft()
  moveForward()
  turtle.turnLeft()
 end
 turnR = not turnR
end