url = github:lopsided98/nix-ros-overlay; }; outputs = { self, nixpkgs, rospkgs }: let distro = "humble"; system = "x86_64-linux"; pkgs = nixpkgs.legacyPackages.${system}; ros = rospkgs.legacyPackages.${system}.${distro}; in { devShells.${system}.default = pkgs.mkShell { ...