anchor.diff:              get_input_pos(open, Params);
           "u" ->
               get_input_pos(unflag, Params);
  +        "p" ->
  +            print;
           "q" ->
               quit;
           _ ->
  
positive.code: %% Tested manually.
  -spec get_input() -> {flag | open | unflag, ms_server:pos()} | quit.
  get_input() ->
      {ok, Command, Params} = io_lib:fread(
                                "~s",
                                io:get_line("[u]nflag / [f]lag / [o]pen r c or [q]uit: ")),
      case hd(Command) of
          "f" ->
              get_input_pos(flag, Params);
  
negative.code:     io:format("  f 2 3   flags cell at row 2 column 3 as a mine~n"),
      io:format("  u 2 3   clears flag from cell at row 2 column 3~n"),
      io:format("  o 2 3   opens cell at row 2 column 3~n"),
      io:format("  p       display the board again~n"),
      io:format("  q       quits the game~n").
  
  
  