Monday, April 12, 2004

OK, show and tell time. Over the weekend I did quite a bit of exercise, got sick (still am), saw Anne's cousins, went out for 2 breakfasts, played a lot with Luc, and watched the first few lectures in a series from the 80's by Gerald Jay Sussman (GJS) from MIT.

Luc is making progress by the day. I know every kid in the world does, but it's still amazing to watch. He's very happy too, so all those smiles makes playing with him a lot of fun.

The GJS lectures were recommended by DM and AM, and I'm enjoying them. They were taught way back when computing was just starting to become mainstream. The language used is LISP, and it's certainly different. It's the first language I've ever seen which doesn't seem to have any looping constructs, instead doing everything with recursion. That makes me uncomfortable as recursion normally chews up stack space, but I'm starting to suspect that LISP doesn't suffer from that problem. I suppose I'll learn more about this as I go.
(Note: AM explained that LISP uses tail-recursion, which means this isn't an issue for iterative algorithms).

In the meantime I'm going to convert one program in the lecture into C, just so I can see how one part of it works. It's a Newton-Rhapson method for finding square roots, and I want to have a closer look at the differential function. I can follow it reasonably well, but there was a comment about it not being executed on every iteration which didn't seem to be right. There have been some minor errors in the lectures, so I suspect that this might be a slight mis-statement of what was happening. I thought that by translating the code for myself I might get a clearer idea of the exact mechanism.

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