Andrew Helwer
ahelwer.ca · Personal blog · on HN since 2019
Andrew Helwer writes about formal methods like TLA+ and Z3, C++ bugs, security tokens, and quantum computing.
What HN saysHN commenters link his posts comparing Python and TLA+ pseudocode and explaining quantum computing, and one lists his feed among blogs worth following.
16HN people shared it
4linked it in comments
33stories submitted
582story points
6 months agolast shared
2019people per year2026
Most-shared posts
- 1Checking Firewall Equivalence with Z33 people · 5 points · first shared 2021 · discussion on HN
- 2Can sanitizers find the two bugs I wrote in C++?2 people · 12 points · first shared 2023 · 3 comments on HN
- 3Laptops all have built-in security tokens these days2 people · 6 points · first shared 2026 · discussion on HN
- 4Two pictures of quantum computation (2020)2 people · 3 points · first shared 2020 · discussion on HN
- 5Writing a TLA⁺ tree-sitter grammar: my foray into free software2 people · 2 points · first shared 2023 · discussion on HN
- 6Two C++ bugs I found2 people · 2 points · first shared 2023 · discussion on HN
- 7Simulating physical reality with a quantum computer2 people · 2 points · first shared 2019 · discussion on HN
- 8Pseudocode Showdown: Python vs. PlusCal and TLA+2 people · 1 points · first shared 2023 · discussion on HN
- 9The current state of TLA⁺ development1 people · 142 points · first shared 2025 · 42 comments on HN
- 10Doing a math assignment with the Lean theorem prover1 people · 141 points · first shared 2020 · 29 comments on HN
- 11How do you reason about a probabilistic distributed system?1 people · 112 points · first shared 2020 · 15 comments on HN
- 12Let go of StackOverflow; communities must take ownership1 people · 69 points · first shared 2025 · 86 comments on HN
- 13Taking my home work setup seriously: ergonomics and setting in for the long haul1 people · 22 points · first shared 2020 · 2 comments on HN
- 14Google Groups has been left to die1 people · 18 points · first shared 2023 · 9 comments on HN
- 15A supposedly worthwhile contract I'll never do again1 people · 11 points · first shared 2025 · discussion on HN
What HN people wrote when they linked it
jayaprabhakar · 2024-04-15
When publishing algorithms for others' consumption either for a paper or blog, please post the source code.
This post is a follow up of https://ahelwer.ca/post/2023-03-30-pseudocode/
Where Andrew pointed compared executable Python code vs executable model checker PlusCal.
In this blog, I'm showing how to model check Python code with minor changes.
For the curious, model checking is the formal methods technique that explores every possible path to ensure the invariants are met in every case.
ahelwer · 2021-06-10
I made a lecture aimed at such people (I was such a person!), which has proven popular: https://youtu.be/F_Riqjdh2oM
With a follow-up blog post focusing on entanglement: https://ahelwer.ca/post/2018-12-07-chsh/
dotnet00 · 2024-04-06
This seems like a decent explanation of what I had in mind: https://oxsci.org/quantum-computing-for-quantum-chemistry/ and this one a slightly more math based explanation: https://ahelwer.ca/post/2019-12-21-quantum-chemistry/
I'm trying to recall another far less outlandish result (than wormholes) that was also verified via quantum computer, but no dice at the moment.
Edit: I might've been thinking of the simulation of a discrete time crystal on Google's quantum computer: https://physics.aps.org/articles/v14/131
'The researchers stress that this DTC behavior can also, in principle, be simulated on a classical computer. But in that case, “the bits in the computer evolve in a way that looks nothing like the physics we're interested in but nevertheless output numbers that replicate the outcomes of a hypothetical experiment,” Ippoliti says. In contrast, on a quantum computer, the qubits themselves exhibit the DTC behavior.'