Eigenmumbles

A commonplace book is a sort of journal for keeping track of quotes, references, ideas, and other odds and ends. These books were once more common than they are now, I think, though there are still those who keep something similar (I’m a big fan of Cosma Shalizi’s notebooks, for example).

I keep notes on a variety of topics, but some are scattered throughout my filesystem and others spill onto a zillion scraps of paper. And every so often, I find myself explaining some trick or idea – yesterday it was the representation of complex numbers as two-by-two matrices, today it was the idea that doubling the available storage when expanding an array can ensure bounded amortized copy overhead per element. And I think, “if I kept better notes about when I learn tricks like this, I would probably be able to tell them where I learned this.” But at the time, it seemed more interesting to learn these tricks and start using them than to write down where I first saw them. Ah, well.