anchor.diff:  
       mkdir -p "$out/bin" "$out/share/gap/"
   
  -    mkdir -p "$out/share/gap"
       echo "Copying files to target directory"
       cp -ar . "$out/share/gap/build-dir"
   
  
positive.code: , makeWrapper
  , readline
  , gmp
  # one of
  # - "minimal" (~400M):
  #     Install the bare minimum of packages required by gap to start.
  
negative.code: stdenv.mkDerivation rec {
    pname = "gap";
    # https://www.gap-system.org/Releases/
    version = "4.11.0";
  
    src = fetchurl {
      url = "https://files.gap-system.org/gap-${lib.versions.major version}.${lib.versions.minor version}/tar.bz2/gap-${version}.tar.bz2";
      sha256 = "sha256-vwcKENwqxgWT/mXfD4c9ctTWdQHobrJipva9SPyGhgI=";
    };
  
    # remove all non-essential packages (which take up a lot of space)
  