possible bug... dig error

I may sound like a complete noob when I ask this but here it goes.
I am trying to make a lumberjack script on a mining turtle. I finished the script and ran it and it seemed like it was working except for one thing. It wasn't digging the tree blocks. I then entered type in the following:
lua
turtle.dig()

and what I got was

false

it didn't dig it just printed false

what am I doing wrong?

Do you have a diamond pickaxe on the turtle? If not, it will never print true, because there is nothing to dig with. Otherwise, try it with another block type. And make sure the turtle is facing the right way.