Phil's new first rule of computer science lecturing : don't attempt to demonstrate an imperative quicksort by stepping through it on the whiteboard. Especially when you haven't tried it at home, first.

Firstly it's very long. Secondly it's easy to make a mistake.

A horrible lecture yesterday. I fell into one of those "mumbling into the whiteboard for 20 minutes with my back to the students" traps. Having started manually running through the quicksort, I found, after about 6 or 7 minutes that I'd made a mistake, coming out of the first "increase-the-lower-bound while loop" too early. I appologised and went back to correct it, but it became extremely clear that actually working through the algorithm until the list was sorted would take far longer than I wanted to spend, and the students were already ignoring me and chatting among themselves. Admitedly some were looking at the paper copy I'd given them and trying to work it out. Others were staring glassy eyed at me. So I asked if they preferred to work through it themselves or for me to continue. No one answered. Eventually one guy indicated that I should continue, but as I turned back I could tell perfectly well that even he wasn't really paying attention or following what I was saying. I panicked and took refuge in trying to work through it again for five minutes and then gave up. "It does work" I tried to assure them, lamely. "Let's look at the Haskell version."

But by then I really didn't have the presence to summon their attention back. And my vocabulary and any semblance of grammatical competence had completely disintegrated. Even the recursive version takes time to demonstrate, and the audience were restive. Was I going to expect them to do the exercises before they left? No, I relented. This time they could take them home. That was the basic cue for some to start to get up and leave. "If anyone has any problems understanding this, come up and see me now and I'll explain individually" I invited. No one took me up on the offer.

One student who had already taught quicksort on another course, took pity on me and came up and started to demonstrate that my program ''did'' really work. I let the others drift off without a word. A couple of the students stayed behind and finished their exercise. Their verdict : the Python was very complicated, but the Haskell was interesting and kind of self-explanatory. Guess I was wrong!

So, at the end of an amazing first week, I've given four classes : two in "Advanced Programming", two in "Programing Languages". All, more or less, in a language I can't actually speak. I started terrified. Gained confidence. Lost it all again in that last lecture. The only solution for next week is yet more preparation and I'm feeling totally snowed under as it is. But it is fun! At least for the moment.