Lean Focused Research Organization
Supporting the Formal Mathematics revolution
- From The Geometry of Machine Learning at Harvard CMSA in Sept: Jared Duker Lichtman's talk explores Math, Inc. Gauss's contributions to number theory and how these results are being formalized in #LeanLang. Watch here: www.youtube.com/watch?v=Ko-P...
- Looking for a lemma in #LeanLang / #Mathlib but don't know its name? Use Loogle! to search: By pattern: _ * (_ ^ _) finds expressions matching the pattern By conclusion: |- tsum _ = _ * tsum _ finds specific conclusion shapes Combine searches with commas for precision! loogle.lean-lang.org
- 𝐋𝐞𝐚𝐧 𝟒.𝟐𝟒.𝟎 𝐢𝐬 𝐥𝐢𝐯𝐞! This release improves the module system, strengthens the 𝚐𝚛𝚒𝚗𝚍 tactic, and advances the standard library. Key improvements: 3.5x faster auto-completion, streamlined "try this" suggestions, new 𝚐𝚛𝚒𝚗𝚍 AC solver, enhanced 𝚖𝚟𝚌𝚐𝚎𝚗 syntax. Read more: lean-lang.org/doc/referenc...
- Tactic tip: Lean's 𝚜𝚒𝚖𝚙? is an optimization tool that shows the minimal 𝚜𝚒𝚖𝚙 𝚘𝚗𝚕𝚢 call needed to close a goal. Use the 𝚜𝚒𝚖𝚙? "Try this" suggestion to insert the precise 𝚜𝚒𝚖𝚙 𝚘𝚗𝚕𝚢 call into your proof. Learn more: lean-lang.org/theorem_prov... #LeanLang #LeanProver #ProofAssistant
- "Theorem Proving in Lean 4" is the essential guide for anyone using Lean for mathematical proofs. Kept up-to-date with each new Lean release, it covers everything from basic tactics to advanced proof strategies. Read the book here: lean-lang.org/theorem_prov... #LeanLang #LeanProver #Mathematics
- Reservoir is #LeanLang's package registry, inspired by crates.io (thanks @rustfoundation.org!) Browse community-created packages and discover new tools: reservoir.lean-lang.org Sharing is easy! GitHub repos meeting the inclusion criteria are auto-indexed: reservoir.lean-lang.org/inclusion-cr...
- Speed up your #LeanLang workflow in #VSCode with shortcuts: ℹ️Ctrl/Cmd+Shift+Enter: Open the InfoView 🔡Ctrl/Cmd+Shift+O: List current file declarations, namespaces and sections 🔄Ctrl/Cmd+Shift+X: Restart the current file See more in the Lean VS Code extension manual: github.com/leanprover/v...
- #LeanLang office hours are tomorrow (Wednesday the 15th) at 23:00 UTC. Bring your questions, share your projects, or just come to learn from others in the community. ➡ Find calendar and meeting links on our website: lean-lang.org/community/#e...
- New use case on our website: AWS's Cedar authorization policy language verified with Lean, using "verification-guided development", and integrated into Cedar's development workflow. ➡️Read more: lean-lang.org/use-cases/ce... #LeanLang #LeanProver #CedarPolicy #FormalVerification #AWS
- 💡Did you know you can run #LeanLang in your browser without installing anything? The Lean Playground provides a full environment for experimentation, learning, and for sharing code snippets with others. Try it out! live.lean-lang.org
- [Not loaded yet]
- Yes! You are absolutely correct - oversimplification on my part! 😅 No near-term plans for WASM, but it's always a possibility for much further down the road. Check out our most recent roadmap to see what we're focusing on presently: lean-lang.org/fro/roadmap/...
- The next bi-monthly #Mathlib community meeting is tomorrow (Friday Oct 10) at 2pm UTC. Join to hear about ongoing #LeanLang formalization projects and connect with contributors. See all community events on our website: lean-lang.org/community/?u...
- Did you know the Info View in #LeanLang's #VSCode extension updates in real-time as you write proofs? Click on any part of your code to see the current proof state, goals, and hypotheses at that exact point. Learn more about the Lean VS Code extension: github.com/leanprover/v...
- We really loved this series of tutorials on #metaprogramming in #LeanLang by Heather Macbeth. It's a great intro to a complex topic for novice users of #LeanProver! Pt 1: youtube.com/watch?v=cKvg... Pt 2: youtube.com/watch?v=5er4... Pt 3: youtube.com/watch?v=TJ8T...
- FYI: The tutorials were recorded at @simonsfoundation.org Lean Workshop for Mathematics and Physical Sciences. Read more here: leanprover-community.github.io/blog/posts/s...
- Two great talks at #HLF25 last week: Sanjeev Arora on superhuman AI mathematicians using #LeanLang, and David Silver on AI learning through experience with #LeanProver verification. www.youtube.com/watch?v=q9MJ... #AI #FormalMath #ReinforcementLearning
- ICYMI: A great summary on the #LeanLang Community Blog of the @simonsfoundation.org 2025 MPS (Math and Phys Sciences) Workshop on #LeanProver. The post includes links to lecture slides, videos, and a list of proposed projects and participants! leanprover-community.github.io/blog/posts/s...
- Fun to see snippets of #LeanLang interspersed into this fantastic @3blue1brown.com guest video by @bensyversen.bsky.social about Euclid's Elements!
- 🎉 Lean 4.23.0 is here! Includes many usability improvements, including: 🎯 Enhanced 'Go to Definition' supporting type class instances 🔧 Interactive error hints for faster debugging Release notes: lean-lang.org/doc/referenc... #LeanLang #LeanProver #OpenSource #Mathematics #FormalVerification
- Recently came across @filiplajszczak.bsky.social's series formalizing a 1967 math textbook in #LeanLang. Designed for those "with no prior experience with formalization" - nice bridge for newcomers to #LeanProver! Read the intro post here: filip.lajszczak.dev/lean-4-with-...
- If you're you curious about #LeanLang and want to understand the connection between #programming and #proofs, check out this great new video by Ank Yog. The analogy between Chess and true propositions is particularly compelling! www.youtube.com/watch?v=QXQN...
- 🎉 Lean 4.22.0 is here! It represents the culmination of our Year 2 roadmap! Including: 🧠 New grind tactic (SMT-style automated reasoning) 🏗️ New compiler (major performance foundation) Read the release notes: lean-lang.org/doc/reference/latest/releases/v4.22.0/ #LeanLang #LeanProver
- Just saw this post on LinkedIn about a new #DiscreteMath game on the #LeanLang Game Server. The author, Shrey Vivek, won a "Best Poster" award at the SPMS Odyssey Research Symposium. 🎉 The Discrete Math game: adam.math.hhu.de#/g/shreyvive... The LinkedIn post: www.linkedin.com/posts/shrey-...
- Thorsten Altenkirch explains Gödel's Incompleteness Theorem on @computerphile.bsky.social, and shows some definitions in #LeanLang! 🎯 Watch here: www.youtube.com/watch?v=IuX8...
- We're excited to share the Lean FRO Year 3 Roadmap today! It builds on work completed in the first two years of Lean FRO operations and will guide all #LeanLang development through July 2026. ➡️ Read the roadmap at lean-lang.org/fro/ #LeanProver #FormalMathematics #FormalVerification
- The first volume of the new Open Access journal "Annals of Formalized Mathematics" was released today! ➡️ afm.episciences.org/volume/view/... #FormalMath #Mathematics #OpenAccess
- From the journal "Aims and Scope": "We expect papers to be accompanied by formal proof artifacts...[and] reviewers and interested readers to look at code artifacts alongside papers." 🎉
- Markus Himmel has written a blog post about how to write a simple imperative program in Lean and then how to verify that the program is bug-free. markushimmel.de/blog/my-firs...
- Yes! Great post by Markus! And it provides a bit of a preview of some upcoming #LeanLang version 4.22 features. 😏
- In the continuing saga of surprising things users do: This post over on LinkedIn features a custom made #LeanLang environment intended to replace a Jupyter Notebook, because, you know - why not? 👀 www.linkedin.com/posts/philip... (With apologies to @jupyter.org ❤️)
- This is an... unexpected use of the #LeanLang InfoView: unnamed.website/posts/bad-ap... But we love the creativity! #LeanProver #DevTools #Metaprogramming
- [Not loaded yet]
- Right? But incredibly endearing.
- 📣 We're excited to share the new lean-lang.org! Relaunching our website was a key deliverable in our Year 2 roadmap to provide "improved navigation and access to valuable content, resources, and tools." We hope you like it! #LeanLang #LeanProver
- Really enjoyed this talk by @harrisongoldste.in that demonstrates inventive uses of the #LeanLang InfoView enhanced by metaprogramming techniques to display real-time testing data. #LeanProver #Metaprogramming #VSCode #PropertyTesting
- 📣 #LeanLang v4.21 is released! This release brings 295 changes, including feature additions, bug fixes, refactors, documentation improvements and performance improvements, in support of our Y2 roadmap: lean-fro.org/about/roadma... ➡️ See the full changelog here: lean-lang.org/doc/reference/
- would you please check that your links work and are correct before posting. Here is the correct changelog link for v4.21 lean-lang.org/doc/referenc...
- Thanks for the fix!
- Core Memory #22 with @ashleevance.bsky.social features a conversation with @adammarblestone.bsky.social and @anastasiag.bsky.social on science funding and FROs with a segment on #LeanLang and its importance to formal verification and AI research. 🎥 www.youtube.com/watch?v=Gbu6...
- In this 10-minute UCLA Connect talk, Terence Tao provides an accessible and compelling argument for "citizen math" and broad collaboration in research #mathematics via #formalverification using proof assistants like #LeanLang. 🎥 www.youtube.com/watch?v=K376...
- Incredibly grateful to @sigplan.bsky.social and @sigplan-pldi.bsky.social for awarding #LeanLang the Programming Languages Software Award 2025 at #PLDI2025! #LeanProver #FormalMethods #ProgrammingLanguages #Mathematics #SoftwareVerification
- The citation states: "The Lean theorem prover is a remarkable software artifact... Lean has had and continues to have a broad impact on industrial practice and scientific research... formal methods based on Lean will play a central role in mathematics in the years to come".
- This belongs to our amazing community - mathematicians building Mathlib (1.8M+ lines!), engineers at AWS/Microsoft/beyond doing critical verification work, and researchers pushing formal methods forward. Thank you to everyone making formal mathematics and software verification more accessible! 🙏
- Lean won the SIGPLAN Programming Languages Software Award 2025 #LeanLang #LeanProver In a few days there will be a much better text at @lean-lang.org's site, but here is all I could gather today: dev.to/adolfont/lea...
- Thanks for sharing this great write up! We're thrilled that #LeanLang has been acknowledged by the SIGPLAN awards committee with this award. It's truly a testament to all the amazing work the community has accomplished in recent years!
- [Not loaded yet]
- Congrats! We're excited to see what projects come from expMath!
- Cryspen is excited to announce it has been awarded a grant from the Ethereum Foundation to extend our hax verification toolchain with support for the Lean prover. Watch this space for more on this soon! #FormalVerification #Lean #Rust
- Very exciting! Looking forward to learning more!
- 📣 This week, #LeanLang Chief Architect Leonardo de Moura will deliver a keynote in Seoul at #PLDI2025 titled "Lean: Machine-Checked Mathematics and Verified Programming, Past and Future." #pldi #formalmethods #programminglanguages #leanprover
- We're grateful to the PLDI organizers for this opportunity to share Lean's journey with such a vibrant community. For those attending or interested in formal verification, this promises to be an insightful discussion about where our field is headed!
- 🎉 #LeanLang 0.1 was released 11 years ago today! Lean had been in development since July 15, 2013, but Lean 0.1 was a major milestone. The screencap is a @waybackmachine.bsky.social 06/26/2014 snapshot from the @lean-lang.org GitHub, "Updated 10 days ago"! #LeanProver #ProgrammingHistory
- [Not loaded yet]
- Oh gosh. Thanks @haskell.org. 🤩
- We are going to have a talk about #LeanLang at Esquenta SE4FP se4fp.github.io/2025/
- Very exciting! Looking forward to seeing the full agenda!
- If you're interested in keeping up on #LeanLang / #LeanProver news check out the LeanLang feed by @adolfont.github.io! bsky.app/profile/did:...
