loogle

Loogle is a search tool for Lean/Mathlib, and can be used on the web, via a zulip bot, via APIs, from VSCode or nvim extensions as a Lean command or a command line tool.

Try it at https://loogle.lean-lang.org/!

$ loogle '(List.replicate (_ + _) _ = _)'
Found 5 declarations mentioning List.replicate, HAdd.hAdd and Eq.
Of these, 3 match your patterns.

List.replicate_add
List.replicate_succ
List.replicate_succ'

Running locally

The loogle binary searches any Lake project of the same Lean toolchain — your project does not need to depend on loogle. The setup is:

1. Clone this repository and cd into it.

2. Copy the target project's lean-toolchain into this checkout, so the loogle binary is built with the same toolchain as the oleans it will read:

   cp /path/to/project/lean-toolchain .
   

3. Run lake build. This produces the binary at .lake/build/bin/loogle.

4. From the target project, point loogle at the module you want to search:

   lake env /path/to/loogle/.lake/build/bin/loogle \
     --module MyModule "<query>"
   

   The first call builds the search index (slow); by default loogle caches it on disk next to the module's .olean so subsequent calls are fast, and quietly rebuilds it whenever the underlying .oleans change. If the default location is not writable, pass --index-file PATH to choose another, or --index-mode none to skip the cache entirely.

CLI Usage

USAGE:
  loogle [OPTIONS] [QUERY]

OPTIONS:
  --help
  --interactive, -i     read querys from stdin
  --json, -j            print result in JSON format
  --module mod          import this module (default: Mathlib)
  --path path           search for .olean files here (default: the build time path)
  --index-mode MODE     how to manage the on-disk search index. One of:
                          use   (default) load if present and up-to-date,
                                otherwise build and write
                          read  load existing index; refuse to start if it
                                is missing or out of date
                          write always (re)build the index and write it
                          none  build in memory and discard on exit
  --index-file PATH     override the default index path. The default lives
                        next to the root module's .olean (with .loogle-index
                        extension); pass this if that location is read-only.
  --max-results n       limit the number of returned hits (default: 200)

Web service

This tool is the backend of https://loogle.lean-lang.org/. This is currently running on a virtual host with a nixos system with a nginx reverse proxy (for SSL) in front of a small python HTTP server (see ./server.py) that uses loogle. It automatically tries to upgrade to the latest mathlib every 6 hours.

You can run this server locally as well. The wrapper has to run from the loogle checkout (it opens blurb.html, loogle.png, … from the current directory), and pass the directory of the project you want to search via --project-dir:

lake build
./server.py --project-dir /path/to/project -- --module RootModule

The wrapper accepts --host, --port, --loogle-bin, and --project-dir, and forwards any arguments after -- to the loogle binary.

At the path /json?q=… (instead of /?q=…), the result is returned in JSON format. No stability of the format is guaranteed at this point.

Zulip bot

The leanprover Zulip chat has a bot called loogle that will respond to messages with the first two hits from loogle. Just write @**loogle** query in a public stream.

It is implemented via an outgoing webhook to the above web service.

Editor integration

These are created by their respective maintainers; reach out to them if you have questions

• VS Code extension “Loogle Lean”
• lean.nvim has built-in support for loogle.

Declaration filtering

Auto-generated declarations (e.g. injEq, sizeOf_spec, casesOn) are hidden from search results. The filtering logic follows doc-gen4's isBlackListed (see Loogle/BlackListed.lean).

Contact

This tool was created by Joachim Breitner <mail@joachim-breitner.de>. Feel free to use this repository to report issues or (even better) submit PRs that resolves such issues.