This is the repository for Lean 4, which is currently being released as milestone releases towards a first stable release. Lean 3 is still the latest stable release.

About

Quickstart
Walkthrough installation video
Quick tour video
Homepage
Theorem Proving Tutorial
Functional Programming in Lean first chapter is available!
Manual
Release notes starting at v4.0.0-m3
Examples
FAQ

Installation

See Setting Up Lean.

Contributing

Please read our Contribution Guidelines first.

Building from Source

See Building Lean.

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Lean 4 programming language and theorem prover

Apache License 2.0

Languages

Language:Lean 80.8%Language:C++ 17.2%Language:CMake 0.5%Language:Nix 0.3%Language:Python 0.2%Language:Shell 0.2%Language:Swift 0.2%Language:Haskell 0.1%Language:Standard ML 0.1%Language:OCaml 0.1%Language:Makefile 0.1%Language:C 0.0%