Top 5 Lean lean4 Projects

lean4

13 3,687 9.9 Lean

Lean 4 programming language and theorem prover

Project mention: The Mechanics of Proof | news.ycombinator.com | 2024-03-20
mathlib4

10 703 10.0 Lean

The math library of Lean 4

Project mention: A Linear Algebra Trick for Computing Fibonacci Numbers Fast | news.ycombinator.com | 2023-11-06

We essentially implemented this matrix version in Lean/mathlib to both compute the fibonacci number and generate an efficient proof for the calculation.
https://github.com/leanprover-community/mathlib4/blob/master...
In practice this isn't very useful (the definition of Nat.fib unfolds quick enough and concrete large fibonacci numbers don't often appear in proofs) but still it shaves a bit of time off the calculation and the proof verification.
InfluxDB

www.influxdata.com
sponsored

Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
lean4-metaprogramming-book

1 191 7.8 Lean

Project mention: Macro-ts: TypeScript compiler with typesafe syntactic macros (2022) | news.ycombinator.com | 2023-05-30

Lean4 manages to pull off changing the parser on the fly at compile time. You can add new productions, add new syntax node types, and add new tokens. Then define macros or code to process the additional syntax. Here is a sample I found that adds a simple JSX-like syntax starting around line 93 and then uses it at line 169:
https://github.com/leanprover/lean4/blob/master/tests/playgr...
I believe most of the language is defined this way, although it is pre-compiled.
For more details see the lean4 metaprogramming book: https://github.com/arthurpaulino/lean4-metaprogramming-book
std4

1 189 9.7 Lean

Standard Library for Lean 4

Project mention: The Mechanics of Proof | news.ycombinator.com | 2024-03-20
lean4-raytracer

1 113 3.5 Lean

A simple raytracer written in Lean 4

Project mention: Functional Programming in Lean – a book on using Lean 4 to write programs | news.ycombinator.com | 2023-05-29

Lean is currently moving to the 4th iteration which is the first intended to be a general-purpose programming language. It "is currently being released as milestone releases towards a first stable release". For now the main goal is to port mathlib to the new version, and then they will concentrate on the compiler. So it is not production ready. But that doesn't mean it is not suitable for building any programs now. There is a simple raytracer written in Lean [1]. I have built a chip8 interpreter with it and the only problem was the lack of an ecosystem, meaning I had to build the necessary libraries myself.
Now it has a RC GC and boxes everything >= 64 bits, and as the compiler isn't polished it is probably significantly slower. In the referenced raytracer repo you can find rendering time compared to the C implementation (Lean is 25x slower, but that was a year ago).
[1] https://github.com/kmill/lean4-raytracer
WorkOS

workos.com
sponsored

The modern identity platform for B2B SaaS. The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2024-03-20.