Question about which tools to use, bugs, the best way to implement a function, etc should go here. Don't forget to see if your question is answered in the wiki first! When in doubt post here.
LOW_LEVEL_H isn't defined, so the header never gets included. You'll also note the mistake in the second line of your header.
This explains your initial problem, but fixing it then throws up a further one. I think it's a useful exercise for you to try to solve that one yourself.