rec {
  #############################################################################
  # Helpers

  # Source: https://github.com/NixOS/nixpkgs/blob/d61bc96d16ca288c69b798b8e31eca64050098e3/lib/lists.nix
  foldr = op: nul: list:
    let
      len = builtins.length list;
      fold' = n:
        if n == len
        then nul
        else op (builtins.elemAt list n) (fold' (n + 1));
    in
    fold' 0;

  concatMap = op: list:
    let
      concat = (a: b: op a + b);
    in
    foldr concat "" list;

  extractAttrs = attr: list:
    let
      getAttr' = builtins.getAttr attr;
      hasAttr' = builtins.hasAttr attr;
      filteredList = builtins.filter hasAttr' list;
    in
    builtins.map getAttr' filteredList;

  #############################################################################
  # Lua

  mkLuaHeredoc = content: ''
    lua << EOF
    ${content}
    EOF
  '';

  mkLuaRc = contents: concatMap mkLuaHeredoc contents;
}