It's taken four months, but the next release of Logic for Programmers is now available! v0.13 is over 50,000 words, making it both 20% larger than v0.12 and officially the longest thing I have ever written.¹ Full release notes are here, but I'll talk a bit about the biggest changes.

For one, every chapter has been rewritten. Every single one. They span from relatively minor changes to complete chapter rewrites. After some rough git diffing, I think I deleted about 11,000 words?² The biggest change is probably to the Alloy chapter. After many sleepless nights, I realized the right approach wasn't to teach Alloy as a data modeling tool but to teach it as a domain modeling tool. Which technically means the book no longer covers data modeling.

There's also a lot more connections between the chapters. The introductory math chapter, for example, foreshadows how each bit of math will be used in the future techniques. I also put more emphasis on the general "themes" like the expressiveness-guarantees tradeoff (working title). One theme I'm really excited about is compatibility (extremely working title). It turns out that the Liskov substitution principle/subtyping in general, database migrations, backwards-compatible API changes, and specification refinement all follow basically the same general principles. I'm calling this "compatibility" for now but prolly need a better name.

Finally, there's just a lot more new topics in the various chapters. Testing properly covers structural and metamorphic properties. Proofs covers proof by induction and proving recursive functions (in an exercise). Logic Programming now finally has a section on answer set programming. You get the picture.

Next Steps

There's a lot I still want to add to the book: proper data modeling, data structures, type theory, model-based testing, etc. But I've added new material for two year, and if I keep going it will never get done. So with this release, all the content is in!

Just like all the content was in two Novembers ago and two Januaries ago and last July. To make it absolutely 100% for sure that I won't be tempted to add anything else, I passed the whole manuscript over to a copy editor. So if I write more, it won't get edits. That's a pretty good incentive to stop.

I also need to find a technical reviewer and proofreader. Once all three phases are done then it's "just" a matter of fixing the layout and finding a good printer. I don't know what the timeline looks like but I really want to have something I can hold in my hands before the summer.

(I also need to get notable-people testimonials. Hampered a little in this because I'm trying real hard not to quid-pro-quo, so I'd like to avoid anybody who helped me or is mentioned in the book. And given I tapped most of my network to help me... I've got some ideas though!)

There's still a lot of work ahead. Even so, for the first time in two years I don't have research to do or sections to write and it feels so crazy. Maybe I'll update my blog again! Maybe I'll run a workshop! Maybe I'll go outside if Chicago ever gets above 6°F!

Conference Season

After a pretty slow 2025, the 2026 conference season is looking to be pretty busy! Here's where I'm speaking so far:

• QCon London, March 16-19
• Craft Conference, Budapest, June 4-5
• Software Should Work, Missouri, July 16-17
• Houston Functional Programmers, Virtual, December 3

For the first three I'm giving variations of my talk "How to find bugs in systems that don't exist", which I gave last year at Systems Distributed. Last one will ideally be a talk based on LfP.