anchor.diff:    kvm = qemu_kvm; # added 2018-04-25
     latinmodern-math = lmmath;
     letsencrypt = certbot; # added 2016-05-16
  -  leksah = throw "To use leksah, refer to the instructions in https://github.com/leksah/leksah."; # added 2019-04-28
     libaudit = audit; # added 2018-04-25
     libcanberra_gtk2 = libcanberra-gtk2; # added 2018-02-25
     libcanberra_gtk3 = libcanberra-gtk3; # added 2018-02-25
  
positive.code:   wicd = throw "wicd has been removed as it is abandoned."; # added 2021-09-11
    wineStaging = wine-staging; # added 2018-01-08
    winusb = woeusb; # added 2017-12-22
    winstone = throw "winstone is not supported anymore. Alternatives are Jetty or Tomcat."; # added 2019-05-14
    winswitch = throw "winswitch has been removed from nixpkgs."; # added 2019-12-10
    wireshark-gtk = throw "wireshark-gtk is not supported anymore. Use wireshark-qt or wireshark-cli instead."; # added 2019-11-18
    wireguard = wireguard-tools; # added 2018-05-19
  
negative.code:   terraform-provider-lxd = terraform-providers.lxd; # added 2020-03-16
    terraform-provider-nixos = terraform-providers.nixos; # added 2018-09-28
    tesseract_4 = tesseract4; # added 2018-12-19
    tex-gyre-bonum-math = tex-gyre-math.bonum; # added 2018-04-03
    tex-gyre-pagella-math = tex-gyre-math.pagella; # added 2018-04-03
    tex-gyre-schola-math = tex-gyre-math.schola; # added 2018-04-03
  