Certainty by Construction Progress Report 5

The following is a progress report for Certainty by Construction, a new book I’m writing on learning and effectively wielding Agda. Writing a book is a tedious and demoralizing process, so if this is the sort of thing you’re excited about, please do let me know!

Reporting in a little early this week, since I’m going to be traveling for two weeks without my laptop starting tomorrow. That means the book isn’t going to get much work done on it until early July.

Nevertheless, I’ve been busy this week. I looked at a “real” book the other day, and was floored by how beautifully it was typeset. It inspired me to up my game and put a lot more energy into presentation. The results, in my opinion, are stunning. I redid the chapter headings. I changed the page headers. Painfully, I changed the margins too, which left the book 100 pages shorter than it used to be. Ouch! But what I’m most proud of is the new color scheme.

Let’s face it. The out-of-the-box color scheme for Agda is hard to love. It’s got ten seemingly-randomly-chosen colors, all smashed together. At first I tried a black and white color scheme, which looked great, but made the code hard to parse. So instead, I’ve settled on a trichomatic scheme based on the colors from Byrne’s Euclid. It took a lot of tweaking to make everything work, but I’m really happy with how it’s turned out.

But presentation isn’t everything I did this week. No, I also rewrote everything I had on setoids, and have now motivated them by way of a section on monoids and their homomorphisms. This material is also a rewrite of the old janky monoid stuff, and it’s really come together. I’ve been trying to tie in a little more “and, as a programmer, why you should care” about some of these ideas.

Furthermore, there’s some rudimentary new material on finite numbers, characteristic functions and isomorphisms, with the eventual programming tie-in being automatic memoization of functions. This is a topic I thought I understood, but working through the formalization makes me realize I had fooled myself.

Anyway. I’m going to be gone for a few weeks, but I’ll pick right back up when I hit ground again. See you soon.

That’s all for today. If you’ve already bought the book, you can get the updates for free on Leanpub. If you haven’t, might I suggest doing so? Your early support and feedback helps inspire me and ensure the book is as good as it can possibly be.