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https://github.com/leanprover/elan

The Lean version manager
https://github.com/leanprover/elan

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The Lean version manager

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# elan: Lean version manager



*elan* is a small tool for managing your installations of the [Lean theorem prover](https://leanprover.github.io). It places `lean` and `lake` binaries in your `PATH` that automatically select and, if necessary, download the Lean version described in your project's `lean-toolchain` file.

You can also install, select, run, and uninstall Lean versions manually using the commands of the `elan` executable.



```shell

~/my/package $ cat lean-toolchain

nightly-2023-06-27



~/my/package $ lake --version

info: downloading component 'lean'

Total: 181.0 MiB Speed:  17.7 MiB/s

info: installing component 'lean'

Lake version 4.1.0-pre (Lean version 4.0.0-nightly-2023-06-27)



~/my/package $ elan show

installed toolchains

--------------------



nightly (default)

nightly-2022-06-27



active toolchain

----------------



nightly-2023-06-27 (overridden by '/home/me/my/package/lean-toolchain')

Lean (version 4.0.0-nightly-2023-06-27, commit bb8cc08de85f, Release)

```



# Installation



## Manual Installation



**Linux/macOS/Cygwin/MSYS2/git bash/...**: run the following command in a terminal:



```bash

curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh

```



**Windows**: run the following commands in a terminal (Command Prompt or PowerShell ≥ version 7.4.1):

```bash

curl -O --location https://raw.githubusercontent.com/leanprover/elan/master/elan-init.ps1

powershell -ExecutionPolicy Bypass -f elan-init.ps1

del elan-init.ps1

```



Alternatively, on **any supported platform**: Grab the [latest release](https://github.com/leanprover/elan/releases/latest) for your platform, unpack it, and run the contained installation program.



The installation will tell you where it will install elan to (`~/.elan` by default), and also ask you about editing your shell config to extend `PATH`. elan can be uninstalled via `elan self uninstall`, which should revert these changes.



## NixOS



The toolchains downloaded by elan require some patching on NixOS, which is done automatically by the version available in Nixpkgs.

```bash

$ nix-env -iA nixpkgs.elan

```



# Prerequisites



On some systems, `lake` will not work out of the box even if installed through elan:



* You'll need [git](https://git-scm.com/download) to download dependencies through `lake`.



# Implementation



*elan* is basically a fork of [rustup](https://github.com/rust-lang-nursery/rustup.rs). Apart from new features and adaptions to the Lean infrastructure, these are the basic changes to the original code:



* Replaced every mention of `rustup` with `elan`, `cargo` with `lake`, and `rust(c)` with `lean`

* Merged `CARGO_HOME` and `RUSTUP_HOME`

* Removed options to configure host triple



# Build



If you want to build elan from source, you will need to install [Rust](https://www.rust-lang.org/tools/install) and

Cargo and run the following:



```

cargo build

```



The `elan-init` installer will show up in `target/debug`. This is also the main `elan` executable, so can test that it works by running the following:



```

ln -s ./target/debug/elan-init ./elan

./elan --help

```



## Build on Windows



The windows build requires a 64-bit developer command prompt and a Windows version of `perl.exe` which you can download

from [https://strawberryperl.com/](https://strawberryperl.com/). Make sure this downloaded perl.exe is the first thing

in your PATH so that the build does not try and use `C:\Program Files\Git\usr\bin\perl.exe`. The git provided version of

perl doesn't work for some reason.



Then you can run `cargo build` as shown above.