{
  description = "A very basic flake";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-21.05";
  };

  outputs =
    { self
    , nixpkgs
    }:
    let
      allPrograms = [ 1 2 ];
      supportedSystems = [ "x86_64-linux" ];
      forAllSystems = f: nixpkgs.lib.genAttrs supportedSystems (system: f system);
      nixpkgsFor = forAllSystems (system:
        import nixpkgs { inherit system; }
      );
    in
    {
      devShell = forAllSystems
        (system:
          let
            pkgs = nixpkgsFor."${system}";
          in
          with pkgs;
          mkShell {
            nativeBuildInputs = [ gcc ];
          });

      apps = forAllSystems
        (system:
          let
            pkgs = nixpkgsFor."${system}";
            execs = with builtins; map toString allPrograms;
            mkApp = name: with pkgs; stdenv.mkDerivation {
              name = "${name}";
              src = ./src;
              buildInputs = [ gcc ];
              unpackPhase = ''
                true
              '';
              buildPhase = ''
                gcc -o main $src/${name}/main.c -fopenmp
              '';
              installPhase = ''
                install -Dm755 main $out/bin/main
              '';
            };
          in
          with pkgs;
          lib.genAttrs execs (p: {
            type = "app";
            program = "${mkApp p}/bin/main";
          }));
    };
}