anchor.diff:    {ok, "1234"} = runcmd(E, "p"),
     {ok, ["asdf", "1234"]} = runcmd(E, ",p"),
   
  +  {ok, "asdf"} = runcmd(E, "-"),
  +  {ok, "1234"} = runcmd(E, "+"),
  +
     {ok, "asdf"} = runcmd(E, "1"),
  +  {ok, ""} = runcmd(E, "d"),
  +
  +  {ok, "1234"} = runcmd(E, "p"),
  +  {ok, ["1234"]} = runcmd(E, ",p"),
  +
  +  {ok, ""} = runcmd(E, "d"),
   
     ok.
   
  
positive.code:     {From, {setLineNumber, Num}} ->
        From ! {self(), ok},
        fileed(Lines, Num);
      terminate -> ok
    end.
  
  
negative.code:     ",p" -> {ok, sendRecv(E, list)};
      "p" -> {ok, sendRecv(E, print)};
      "d" -> sendRecv(E, delete), {ok, ""};
      "+" -> N = sendRecv(E, getLineNumber),
             sendRecv(E, setLineNumber, N + 1),
             {ok, sendRecv(E, print)};
      "-" -> N = sendRecv(E, getLineNumber),
             sendRecv(E, setLineNumber, N - 1),
             {ok, sendRecv(E, print)};
      _ -> Num = getnum(L),
           NumValid = numValid(E, Num),
           if NumValid -> sendRecv(E, setLineNumber, Num),
                          {ok, sendRecv(E, print)};
              true -> {error, unknown()}
           end
    end.
  