[Haskell-beginners] Tying the knot with binary trees

[Michael Schober]

Hi Markus,

> They say that for this or similar reasons you have to use a zipper,
> but I know nothing more about them than this :-)

Thanks for the hint. I hadn't heard of zippers before and after some 
reading, they indeed seem to do the trick, although I have yet to 
implement it in my solution.

Anyways, here are the resources which worked best for my understanding:

[1] http://en.wikibooks.org/wiki/Haskell/Zippers
[2] http://learnyouahaskell.com/zippers

Best,
Michael