Andrew Helwer

Google Groups has been left to die

Where should the formal methods community move?

Book review: Is parallel programming hard, and, if so, what can you do about it?

Here are my thoughts on the free online textbook Is Parallel Programming Hard, And, If So, What Can You Do About It? by Paul E. McKenney, author of the Linux kernel’s RCU synchronization mechanism. I read a lot of this textbook, got my fill, and probably won’t read more of it in the near future so wanted to write this…

The current state of TLA⁺ development

The 2025 TLA⁺ Community Event was held last week on May 4th at McMaster University in Hamilton, Ontario, Canada. It was a satellite event to ETAPS 2025, which I also attended, and plan to write about in the near future. I gave a talk somewhat-hucksterishly titled It’s never been easier to write TLA⁺ tooling! which I…

Doing a math assignment with the Lean theorem prover

Note: this post was written for Lean 3; the latest version, Lean 4, is a very different language. Turn back the clock to 2009: a confused physics major newly infatuated with math and computer science, I enrolled in MATH 273: Numbers and Proofs at the University of Calgary. This wasn’t my first encounter with…

Can sanitizers find the two bugs I wrote in C++?

A few days ago I published a short post about two bugs I wrote while developing the C++ external scanner for my TLA⁺ tree-sitter grammar. Reactions were mixed! Many people were supportive, but there were of course the usual drive-by claims by developers that the bugs were trivial, they would’ve found & fixed them…

Writing a TLA⁺ tree-sitter grammar: my foray into free software

My foray into free software

How do you reason about a probabilistic distributed system?