Tree cutter

function movetotree()
   for i=1,7 do
      turtle.forward()
   end
end

function drop()
   for d=1,15 do
      turtle.select(i)
      turtle.dropDown()
   end
end

function cut()
   turtle.dig()
   turtle.forward()
   while true do
      if turtle.digUp() then
      turtle.up()
      else if not turtle.down() then
      turtle.back()
      break
      end
   end
end

function movetodrop()
   for g=1,7 do
      turtle.back()
   end
end

function refuel()
   if (turtle.getFuelLevel()=="Unlimited") then
      return true
      end
   turtle.select(16)
   turtle.turnRight()
   turtle.turnRight()
   turtle.suck()
   turtle.refuel(64)
   turtle.select(1)
   turtle.turnLeft()
   turtle.turnLeft()
end

function plant()
   turtle.select(15)
   turtle.place()
   turtle.select(1)
end

function saplings()
   turtle.select(15)
   turtle.turnRight()
   turtle.suck()
   turtle.select(1)
   turtle.turnLeft()
end

while true do
   refuel()
   saplings()
   movetotree()
   for z=1,64 do
      plant()
      sleep(180)
      cut()
   end
   movetodrop()
   drop()
end