{
  description = "Nominal Sets in Lean4";
  inputs = {
    nixpkgs = {
      url = "github:nixos/nixpkgs/nixpkgs-unstable";
    };
    flake-utils = {
      url = "github:numtide/flake-utils";
    };
  };
  outputs = { self, nixpkgs, flake-utils }: flake-utils.lib.eachDefaultSystem (system:
    let
      pkgs = import nixpkgs { inherit system; };
      lean-shell = pkgs.mkShell {
        name = "Lean";
        packages = [ pkgs.lean4 ];
      };
    in {
    devShells = {
      default = lean-shell;
      lean = lean-shell;
    };
  });
}