Just curious -- and be honest -- the snippet at the end they ask you to decipher (and they say "Most programmers find it hard to understand unless they have a functional programming background, so don't feel bad if you don't get it immediately") did you have trouble with it?

For me, I thought I had the answer after maybe 30 seconds of reading it, but decided to "check my work" by walking through it again, and only then, a moment later, did I realize what it was actually doing with that recursive call.

I'm just curious about their "most programmers without a functional background" remark. So: did ya get it?