Wow, I sure stirred up a hornet's nest with my safe navigation experiment. Some people posted some very useful information and good alternative approaches!
As for comments about "ugliness", being able to read this in 6 months, etc.; I'm not making a policy decision here, just experimenting. The fact that people are so put off by experimentation makes me wonder... Anyway, we'll see if it comes in handy or not. Things like this can easily be "compiled" by the mind as "programming idioms".
But as for unreadable, it's only a cascade of lambdas, after all. Personally, I've been very comfortable with functional style, since I first learned LISP, freshman year in college. It's amazing to me how emotional some programmers get when they see code using functional style. Does this mean "imperative -> good, functional -> bad?"
I guess there's always been a divide between functional and imperative approaches. I'm glad Church and Turing could see that their different approaches were accomplishing the same thing. I really think more universities should teach functional languages in their freshman level courses, before people have a chance to ingrain imperative as the one true way. My university (Purdue) did not; I just happened to learn it from a friend, because I was interested in what LISP was and how to use it. At the time, I was amazed (and a bit envious) to find out that some universities taught LISP or Scheme to freshmen.
I think LISP and Scheme are excellent first languages, because they abstract computation away from the machine; they don't encourage you to simulate a computer in your head when you write code. Simulating a stack machine can be a great barrier to actually understanding recursion and higher order functions. Freshman and sophomore year, I helped quite a few students learn recursion, but I had to "unteach" the technique of "stack simulation" first, so they actually had a chance of understanding something like A-B recursion or composite recursion.
It's interesting, because I just started teaching a guy to program last week, and I chose to start with Scheme (although eventually he probably needs to learn Java). I found good site with some basic tutorials and a free book on programming that actually teaches recursion the way I taught it freshman year, way back in 1984. It looks like I'm not the only one with those ideas about how to teach recursion.
For those interested, here's the PLaneT Scheme Site and here's the book (linked from their site as well).