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Start all of your commands with a comma

https://rhodesmill.org/brandon/2009/commands-with-comma/
55•theblazehen•2d ago•10 comments

OpenCiv3: Open-source, cross-platform reimagining of Civilization III

https://openciv3.org/
637•klaussilveira•13h ago•188 comments

The Waymo World Model

https://waymo.com/blog/2026/02/the-waymo-world-model-a-new-frontier-for-autonomous-driving-simula...
935•xnx•18h ago•549 comments

What Is Ruliology?

https://writings.stephenwolfram.com/2026/01/what-is-ruliology/
35•helloplanets•4d ago•30 comments

How we made geo joins 400× faster with H3 indexes

https://floedb.ai/blog/how-we-made-geo-joins-400-faster-with-h3-indexes
113•matheusalmeida•1d ago•28 comments

Jeffrey Snover: "Welcome to the Room"

https://www.jsnover.com/blog/2026/02/01/welcome-to-the-room/
13•kaonwarb•3d ago•11 comments

Unseen Footage of Atari Battlezone Arcade Cabinet Production

https://arcadeblogger.com/2026/02/02/unseen-footage-of-atari-battlezone-cabinet-production/
45•videotopia•4d ago•1 comments

Show HN: Look Ma, No Linux: Shell, App Installer, Vi, Cc on ESP32-S3 / BreezyBox

https://github.com/valdanylchuk/breezydemo
222•isitcontent•13h ago•25 comments

Monty: A minimal, secure Python interpreter written in Rust for use by AI

https://github.com/pydantic/monty
214•dmpetrov•13h ago•106 comments

Show HN: I spent 4 years building a UI design tool with only the features I use

https://vecti.com
324•vecti•15h ago•142 comments

Sheldon Brown's Bicycle Technical Info

https://www.sheldonbrown.com/
373•ostacke•19h ago•94 comments

Hackers (1995) Animated Experience

https://hackers-1995.vercel.app/
478•todsacerdoti•21h ago•237 comments

Microsoft open-sources LiteBox, a security-focused library OS

https://github.com/microsoft/litebox
359•aktau•19h ago•181 comments

Show HN: If you lose your memory, how to regain access to your computer?

https://eljojo.github.io/rememory/
278•eljojo•16h ago•165 comments

An Update on Heroku

https://www.heroku.com/blog/an-update-on-heroku/
407•lstoll•19h ago•273 comments

Dark Alley Mathematics

https://blog.szczepan.org/blog/three-points/
85•quibono•4d ago•21 comments

PC Floppy Copy Protection: Vault Prolok

https://martypc.blogspot.com/2024/09/pc-floppy-copy-protection-vault-prolok.html
57•kmm•5d ago•4 comments

Delimited Continuations vs. Lwt for Threads

https://mirageos.org/blog/delimcc-vs-lwt
26•romes•4d ago•3 comments

Vocal Guide – belt sing without killing yourself

https://jesperordrup.github.io/vocal-guide/
16•jesperordrup•3h ago•10 comments

How to effectively write quality code with AI

https://heidenstedt.org/posts/2026/how-to-effectively-write-quality-code-with-ai/
245•i5heu•16h ago•193 comments

Was Benoit Mandelbrot a hedgehog or a fox?

https://arxiv.org/abs/2602.01122
14•bikenaga•3d ago•2 comments

Introducing the Developer Knowledge API and MCP Server

https://developers.googleblog.com/introducing-the-developer-knowledge-api-and-mcp-server/
54•gfortaine•11h ago•22 comments

I spent 5 years in DevOps – Solutions engineering gave me what I was missing

https://infisical.com/blog/devops-to-solutions-engineering
143•vmatsiiako•18h ago•64 comments

Understanding Neural Network, Visually

https://visualrambling.space/neural-network/
284•surprisetalk•3d ago•38 comments

I now assume that all ads on Apple news are scams

https://kirkville.com/i-now-assume-that-all-ads-on-apple-news-are-scams/
1061•cdrnsf•22h ago•438 comments

Learning from context is harder than we thought

https://hy.tencent.com/research/100025?langVersion=en
179•limoce•3d ago•96 comments

Why I Joined OpenAI

https://www.brendangregg.com/blog/2026-02-07/why-i-joined-openai.html
137•SerCe•9h ago•124 comments

Show HN: R3forth, a ColorForth-inspired language with a tiny VM

https://github.com/phreda4/r3
70•phreda4•12h ago•14 comments

Female Asian Elephant Calf Born at the Smithsonian National Zoo

https://www.si.edu/newsdesk/releases/female-asian-elephant-calf-born-smithsonians-national-zoo-an...
28•gmays•8h ago•11 comments

FORTH? Really!?

https://rescrv.net/w/2026/02/06/associative
63•rescrv•21h ago•23 comments
Open in hackernews

Z3 API in Python: From Sudoku to N-Queens in Under 20 Lines (2015)

https://ericpony.github.io/z3py-tutorial/guide-examples.htm
155•amit-bansil•2mo ago

Comments

skopje•2mo ago
Very good to see all this in one short page!
stevesimmons•2mo ago
It's worth noting these notes are 11 years old. The first give-away was the comment that in Python 3/2 is an integer, which is indeed true in Python 2 but not in Py3.

For modern users of Z3, you'd want to do `pip install z3-solver` rather than use `Z3Py` mentioned at the very bottom of this doc.

almostgotcaught•2mo ago
https://www.hakank.org/z3/
__alexander•2mo ago
Thank you for the link.
brap•2mo ago
That’s a very clean API.
cess11•2mo ago
It's very close to the SMTLIB API.

Page 19 in https://smt.st/SAT_SMT_by_example.pdf shows an example in both Python and SMTLIB. After looking at a guide like TFA this book is a good next step.

tombert•2mo ago
Solvers are something that still kind of feel like magic to me. I have done a fair amount of Isabelle, and the "sledgehammer" tool in there (which uses solvers to see if an existing proof can be made to work to solve your subgoal) is something that impresses me every single time I use it.
nextaccountic•2mo ago
On same level of abstraction I think it's useful to view those tools as some form of constraint solving. Think how you can solve sudoku with pen and paper by writing out each possibility, then fill squares either because it has only one possibility or by making guesses. After you fill a square, you can then update your possible states (propagate constraints), and repeat until you solve it or hit an impossible solve (in which case you need to backtrack on some earlier guess).

The algorithms differ mainly in how they keep track of all possibilities and how they update them

I think this answer is pretty good https://cstheory.stackexchange.com/a/29428 (take note at the end "sat is csp on boolean domains")

tyilo•2mo ago
I have created a Python library called "z4-solver" that adds some nice utility functions on top of z3: https://github.com/Tyilo/z4

I always use that instead of the z3-solver directly.

Recursing•2mo ago
Have you tried to compare Z3 with cvc5? https://cvc5.github.io/docs/cvc5-1.1.2/api/python/pythonic/p...

It offers basically the same API and could be faster in many cases

gignico•2mo ago
I was about to comment the same. Z3 always takes all the credit but cvc5 is just as great!
raphman•2mo ago
"SAT/SMT by Example" also contains many Z3 examples (and has a new URL): https://smt.st/
philzook•2mo ago
I'm a fan. I've been building a proof assistant directly on the z3py api. https://pypi.org/project/knuckledragger/0.1.3/
gbacon•2mo ago
We care about Z3 because it is a Satisfiability Modulo Theories (SMT) solver.

Satisfiability: In 1971, Stephen A. Cook established that Boolean satisfiability, given an arbitrary Boolean formula whether an assignment to its variables exists that evaluates true, is NP-complete.

https://dl.acm.org/doi/10.1145/800157.805047

Translating between NP-complete problems is at most a polynomial (“fast”) amount of work, so every improvement gained on satisfiability (whose worst case is exponential rather than polynomial time complexity) benefits all other NP-complete problems, and thus the rest of NP.

Modulo Theories: We can think of SMT as a high-level language that automates encoding of other problems into raw Boolean formulas. Applications built on Z3 outsource search by encoding problems via one or more theories and then decoding results back to the problem domain at hand.

The benefits of doing this are (1) using an existing robust, well-tested suite of algorithms where (2) lots of research effort is concentrated and (3) improvements to Z3 improve your problem’s results more-or-less for free. According to Microsoft, “Z3 is used in a wide range of software engineering applications, ranging from program verification, compiler validation, testing, fuzzing using dynamic symbolic execution, model-based software development, network verification, and optimization.”

https://www.microsoft.com/en-us/research/project/z3-3/

See also:

https://github.com/Z3Prover/z3