[Erlang_Question22]如何按规则位数输出数字

%%使用Io:fromat来输出~F.P.PadModC.
%% ~F. ---> ~4. 宽度为F
%% P.  ---> . 无精度要求
%% Pad ---> 0 用Pad填充
%% Mod --->   没有控制序列修饰符指定
%% C   ---> B 控制为10进制输出
%%
format_integer_8_digit(Num) ->
   lists:flatten(io_lib:format("~8..0B", [Num])).

%%使用string:right来构造
format_integer_8_digit2(Num)when is_integer(Num) ->
  string:right(integer_to_list(Num),8,0);
format_integer_8_digit2(NumList) ->
  string:right(NumList,8,0).

format_integer_8_digit3(Number, Padding) when Number < 0 ->
  [$- | format_integer_8_digit3(-Number, Padding - 1)];
format_integer_8_digit3(Number, Padding) ->
  NumberList = integer_to_list(Number),
  ZeroesNeeded = max(Padding - length(NumberList), 0),
  lists:flatten([lists:duplicate(ZeroesNeeded, $0), NumberList]).