Learn Lean
Lean is a functional programming language and theorem prover built for formalizing math and for formal verification, but is flexible enough for general coding. If you’re a beginner, we recommend the Natural Number Game. If you feel ready to dive deeper, there are great textbooks, tutorials and interactive games to be found on this page.
Core documentation
Functional Programming in Lean (FPIL) is the main resource for programmers who want to learn Lean. It assumes a background in programming, but no prior knowledge of functional programming is needed.
Theorem Proving in Lean (TPIL) is designed to teach you to develop and verify proofs in Lean and covers dependent type theory, automated proof methods, and Lean-specific features for interactive theorem proving.
Mathematics in Lean (MIL) is the main resource for mathematicians who want to learn mathematical formalization through interactive, tactic-based theorem proving using Lean's Mathlib library.
The Lean Language Reference is a comprehensive, precise description of Lean: a reference work in which all aspects of Lean are clearly specified, and demonstrated through succinct examples.
Lean FAQ Answers to commonly asked questions about Lean
Further reading
Mathlib API Reference Includes reference information for Lean core, the Lean standard library, Mathlib, and other critical Lean packages.
The Hitchhiker's Guide to Logical Verification Originally designed as a companion text for a graduate-level course on interactive theorem proving at Vrije Universiteit Amsterdam.
Logic and Proof A textbook teaching the basics of classical logic, such as propositional logic, first order logic, natural deduction and axiomatic reasoning, using Lean.
The Mechanics of Proof Originally written as a companion text to the course Math2001 at Fordham University, it teaches the basics of mathematical reasoning to students of mathematics using Lean.
Founder's Blog Essays about Lean development, proof assistants and AI, written by Chief Architect Leo de Moura.
Interactive Games and Tutorials
The Natural Number Game A gamified introduction to mathematical proof that introduces Lean 4 concepts through a purpose-built Lean 4 dialect.
The Lean Game Server A collection of games similar to the Natural Number Game.
Tools for working with Lean
Lean 4 VS Code Extension Manual Describes how to interact with Lean 4 using the VS Code extension.
Semantic Highlighting Configuring Lean's semantic highlighing (enabled in VSCode by selecting "Editor > Semantic Highlighting"
LaTeX Best practices for highlighting Lean code in LaTeX documents
Resources
Loogle! A Lean and Mathlib search tool for finding definitions and lemmas, available on the web, via CLI or through IDE extensions.
Verso A platform for writing documents, books, course materials, and websites with Lean.
LeanExplore A natural language search engine for Lean declarations, indexing commonly used Lean libraries.
LeanSearch A Mathlib search engine for finding tactics and theorems via natural language queries.
LeanDojo A tool for data extraction and interacting with Lean programmatically.
REPL An interactive Read-Eval-Print Loop (REPL) for Lean intended for machine-to-machine interaction and AI applications.
Pantograph A machine-to-machine interaction system that provides interfaces to execute proofs, construct expressions, and examine the symbol list of a Lean project for machine learning.
Lean4Web A web-based version of Lean that allows you to run Lean code directly in your browser.
How to cite Lean
Lean 4
To cite Lean 4 please reference The Lean 4 Theorem Prover and Programming Language published in CADE-28 - The 28th International Conference on Automated Deduction. PDF
Bibtex
@inproceedings{10.1007/978-3-030-79876-5_37,
title = {The Lean 4 Theorem Prover and Programming Language},
author = {de Moura, Leonardo and Ullrich, Sebastian},
year = {2021},
isbn = {978-3-030-79875-8},
publisher = {Springer-Verlag},
address = {Berlin, Heidelberg},
url = {https://doi.org/10.1007/978-3-030-79876-5_37},
doi = {10.1007/978-3-030-79876-5_37},
abstract = {Lean 4 is a reimplementation of the Lean interactive theorem prover (ITP) in Lean itself. It addresses many shortcomings of the previous versions and contains many new features. Lean 4 is fully extensible: users can modify and extend the parser, elaborator, tactics, decision procedures, pretty printer, and code generator. The new system has a hygienic macro system custom-built for ITPs. It contains a new typeclass resolution procedure based on tabled resolution, addressing significant performance problems reported by the growing user base. Lean 4 is also an efficient functional programming language based on a novel programming paradigm called functional but in-place. Efficient code generation is crucial for Lean users because many write custom proof automation procedures in Lean itself.},
booktitle = {Automated Deduction – CADE 28: 28th International Conference on Automated Deduction, Virtual Event, July 12–15, 2021, Proceedings},
pages = {625–635},
numpages = {11}
}
Lean 3
To cite Lean 3 please reference The Lean Theorem Prover (System Description) published in Lecture Notes in Computer Science. PDF.
Bibtex
@inproceedings{inproceedings,
author = {de Moura, Leonardo and Kong, Soonho and van Doorn, Floris and von Raumer, Jakob},
year = {2015},
month = {08},
pages = {378-388},
title = {The Lean Theorem Prover (System Description)},
volume = {9195},
isbn = {978-3-319-21400-9},
doi = {10.1007/978-3-319-21401-6_26}
}