functional-programming - Erlang 列出 :filter returns "\n\f"

Question

我正在函数式编程类(class)中开展一个学校项目。该项目旨在确定一组多米诺骨牌(表示为 1-6 中两个数字的元组列表)是否可以首尾相连。我对这个问题没问题，但我遇到了一个问题，其中 lists:filter 返回字符串 "\n\f" 而不是类似的列表在 documentation 中说.

我在网上找不到任何东西，想知道你们是否有任何想法。

谢谢!

这是我的代码。问题出在 check_dominos() 函数中。

-module(challenge).
-export([test/0, check_dominos/1]).


% If there is an even number of each number, true
% else, false

extract_numbers([]) -> [];
extract_numbers([{First, Second} | T]) -> [First] ++ [Second] ++ extract_numbers(T). 

add_matching_numbers(_Previous, []) -> [];
add_matching_numbers(Previous, [First | T]) when Previous =:= First-> [Previous + First | add_matching_numbers(First, T)];
add_matching_numbers(_Previous, [First | T]) -> add_matching_numbers(First, T).


check_dominos(Dominos) -> 
    All_Numbers = extract_numbers(Dominos),
    Sorted_Numbers = lists:sort(All_Numbers),
    Accumulated_Numbers = add_matching_numbers(0, Sorted_Numbers) ,

    Filter_Lambda = fun(Num) -> Num rem 2 == 0 end,
    Result = lists:filter(Filter_Lambda, Accumulated_Numbers),

    Result.

    % Still working on the logic of this part
    %case length(Accumulated_Numbers) =:= length(Result) of 
    %    true -> true;
    %    _ -> false
    %end.

test() ->
    Test_1 = [{1, 3}, {3, 2}, {2, 1}], % Already in order
    Test_2 = [{5, 2}, {5, 6}, {6, 3}, {1, 4}], % Shouldn't work
    Test_3 = [{2, 6}, {3, 5}, {1, 4}, {3, 4}, {6, 1}, {2, 5}], % Should work

    true = check_dominos(Test_1),
    false = check_dominos(Test_2),
    true = check_dominos(Test_3).

Answer 1

Erlang 字符串是字符代码列表，默认情况下 Erlang shell 会尝试将整数列表显示为字符串。要更改此行为，请在运行程序之前调用 shell:strings(false).。