Turtle Tree Chopper

bonemeal = true
boneslot = 16
sapslot = 15
startslot = 1
lastslot = 14
-----------------
pos = 0

while true do
    turtle.select(sapslot)
    turtle.place()
    if (bonemeal == true) then
        turtle.select(boneslot)
        turtle.place()
        while (turtle.up() == false) do
            turtle.digUp()
            turtle.attackUp()
        end
        pos = 1
    else
        while (turtle.up() == false) do
            turtle.digUp()
            turtle.attackUp()
        end
        pos = 1
        while (turtle.detect() == false) do
            sleep(1)
        end
    end
    turtle.select(startslot)
    while (turtle.detect() == true) do
        while (turtle.up() == false) do
            turtle.digUp()
            turtle.attackUp()
        end
        pos = pos + 1
    end
    while (turtle.forward() == false) do
        turtle.dig()
        turtle.attack()
    end
    for i=1, pos do
        while (turtle.down() == false) do
            turtle.digDown()
            turtle.attackDown()
        end
    end
    while (turtle.back() == false) do
        sleep(.5)
    end

    if (turtle.getItemCount(lastslot) > 0) then
        turtle.turnRight()
        turtle.turnRight()
        for i=startslot, lastslot do
            turtle.select(i)
            turtle.drop()
        end
        turtle.turnRight()
        turtle.turnRight()
    end
end