anchor.diff: -{ stdenv, fetchurl, zlib, bzip2, pkgconfig, curl, lzma, gettext
  +{ stdenv, fetchurl, zlib, bzip2, pkgconfig, curl, lzma, gettext, libiconv
   , sdlClient ? true, SDL, SDL_mixer, SDL_image, SDL_ttf, SDL_gfx, freetype, fluidsynth
   , gtkClient ? false, gtk2
   , server ? true, readline
  
positive.code: 
    nativeBuildInputs = [ pkgconfig ];
  
    buildInputs = [ zlib bzip2 curl lzma gettext ]
      ++ optionals sdlClient [ SDL SDL_mixer SDL_image SDL_ttf SDL_gfx freetype fluidsynth ]
      ++ optionals gtkClient [ gtk2 ]
      ++ optional server readline
  
negative.code:     license = licenses.gpl2;
  
      maintainers = with maintainers; [ pierron ];
      platforms = platforms.unix;
    };
  }
  