The "batteries included" extended library for Lean 4. This is a collection of data structures and tactics intended for use by both computer-science applications and mathematics applications of Lean 4.

Using batteries

To use batteries in your project, add the following to your lakefile.lean:

require batteries from git "" @ "main"

Additionally, please make sure that you're using the version of Lean that the current version of batteries expects. The easiest way to do this is to copy the lean-toolchain file from this repository to your project. Once you've added the dependency declaration, the command lake update checks out the current version of batteries and writes it the Lake manifest file. Don't run this command again unless you're prepared to potentially also update your Lean compiler version, as it will retrieve the latest version of dependencies and add them to the manifest.

Build instructions

  • Get the newest version of elan. If you already have installed a version of Lean, you can run
    elan self update
    If the above command fails, or if you need to install elan, run
    curl -sSf | sh
    If this also fails, follow the instructions under Regular install here.
  • To build batteries run lake build. To build and run all tests, run make.
  • If you added a new file, run the command scripts/ to update the imports.


You can generate batteries' documentation with

# if you're generating documentation for the first time
> lake -R -Kdoc=on update
# actually generate the documentation
> lake -R -Kdoc=on build Batteries:docs
> ls build/doc/index.html

After generating the docs, run lake build -R to reset the configuration.

The top-level HTML file will be located at build/doc/Batteries.html, though to actually expose the documentation as a server you need to

> cd build/doc
> python3 -m http.server
Serving HTTP on :: port 8000 (http://[::]:8000/) ...

Note that documentation for the latest nightly of batteries is available as part of the Mathlib 4 documentation.


Every pull request should have exactly one of the status labels awaiting-review, awaiting-author or WIP (in progress). To change the status label of a pull request, add a comment containing one of these options and nothing else. This will remove the previous label and replace it by the requested status label.

One of the easiest ways to contribute is to find a missing proof and complete it. The proof_wanted declaration documents statements that have been identified as being useful, but that have not yet been proven.

In contrast to mathlib, batteries uses pull requests from forks of this repository. Hence, no special permissions on this repository are required for new contributors.

You can change the labels on PRs by commenting one of awaiting-review, awaiting-author, or WIP. This is helpful for triage.