ACL2 vs Lean
ACL2
acl2.org
Lean
lean-lang.orgSide by side
| Figure | ACL2 | Lean |
|---|---|---|
| Price from | — | Free |
| Free plan | — | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | — | Yes |
| Windows | Yes | Yes |
| macOS | Yes | Yes |
| Linux | Yes | Yes |
| Self-hosted | Yes | — |
| Plans published | 0 | 1 |
| Spec score · Formal Verification Tools | 7.8 (#14) | 8.6 (#2) |
| Support | ACL2 users can get help through the acl2-help mailing list, which the site recommends to new users. | The Lean Community Zulip is described as the central hub for questions and collaboration, and Lean FRO hosts weekly technical office hours. |
Plans
In their own words
Lean
Lean is an open-source programming language and proof assistant for formalizing mathematics, verifying software, and writing general code. Its minimal trusted kernel checks proofs, and the project describes it as supporting correctness in mathematical, software, and hardware verification. Lean includes the Grind tool for automating some pattern matching, case analysis, and systems of linear inequalities; metaprogramming lets users add notation and proof automation. Projects are managed with Lake, the package manager bundled with Lean. Mathlib is a community-driven library with over a million lines spanning areas including algebra, analysis, topology, probability, and computer science. The recommended setup uses VS Code with the Lean 4 extension for syntax highlighting and code completion, while Neovim with lean.nvim is also well-supported. Lean runs on Linux, macOS, and Windows, and Lean4Web lets users run code in a browser. The software is free under the Apache 2.0 license. Learning resources include textbooks, tutorials, interactive games, documentation, and an API reference.