From one of my students:

>> Do you like exercises like this, or should we just stick to the stuff in
>> the books?
> Both. But I like exercises like these more because stuff that's in the
> book, I can do on my own when I have the time. Stuff like this is
> different, and interesting.

I should keep that in mind. =) Stuff that’s in the book I can suggest
for practice, but in class, let’s do something unusual and useful.