Test discussion, and propositional variables

I think the test went well? It's difficult to say. It was one of those tests where at no point was answering anything problematic in some way, and at no point did I run into something that looked like it could have been an error ... but at the same time I'd feel genuinely queasy claiming I aced it. Maybe I'm just being superstitious. At any rate I think I'll have to see what happens when it gets returned.

Not finding structural induction on the test made me a bit sad, which might be because I'd focussed much of my studying on structural induction because a part of it still kind of eludes me. I'd done a bit of studying on this because I feel like it's one of those things I "understand" but don't fully understand. Superficially, it's pretty simple to just say that structural induction is just a little more abstract a version of the other induction flavours we've seen. But I think that explanation is - in addition to being a little too vague - eliminating the question of what is a propositional variable anyway.