anchor.diff:    genByte = s: n: toString (hexByteToInt (
       substring n 2 (mkMAC s)
     ));
  -
  -  netPrefix = "10.${genByte cfg.name 0}.";
   
     instanceOpts = { name, config, lib, ... }: {
       imports = [
  
positive.code:     options = {
        ip = mkOption {
          type = types.str;
          default = "${netPrefix}${genByte name 0}.${genByte name 3}";
        };
  
        mac = mkOption {
  
negative.code:         gid="$(id -g)"
          pwd="$(pwd)"
          starttime="$(now)"
          subnet="$(($RANDOM % 255))"
  
          function log() {
            printf "%05d %s\n" $(($(now) - $starttime)) "$1"
  