lean4-htt/doc/quickstart.md

Quickstart

These instructions will walk you through setting up Lean using the "basic" setup and VS Code as the editor. See Setup for other ways and more details on setting up Lean.

1. Install the latest Lean 4 nightly through elan: in any bash-compatible shell, run

   $ curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh -s -- --default-toolchain leanprover/lean4:nightly
   

   Alternatively, on Windows, download the latest release and run the contained elan-init.exe.
   See the elan link above for other installation options and details.
2. Install VS Code.
3. Open VS Code and install the lean4 extension.
   
4. Create a new file with the extension .lean and add the following code:

   import Leanpkg
   
   #eval Leanpkg.leanVersionString
   

   You should get a syntax-highlighted file with a "Lean Infoview" on the right that tells you the installed Lean version when placing your cursor on the last line.
   
5. You are set up! Try opening a Lean package with a leanpkg.toml. You can create your own packages using leanpkg init on the command line. Packages have to be opened using "File > Open Folder..." for imports to work. Saved changes are visibly in other files after running "Lean 4: Refresh File Dependencies" (Ctrl+Shift+X) in them.