在列表中查找字符串 - Erlang

Question

我正在尝试查找某些字符串是否真的在列表中。有我的代码：

comparing() ->
    FileName = "msg-0001",
    {ok,[NumLine],_} = io_lib:fread("msg-~d",FileName),
    io:format("Numline:~p~n", [NumLine]),
    {ok, Pars} = file:read_file("parsing.txt"),
    {ok, Dump} = file:read_file("msg-0001"),
    StringNumline = lists:flatten(io_lib:format("~p", [NumLine])),
    io:format("StringNumline:~p~n", [StringNumline]),
    StringDump = lists:flatten(io_lib:format("~p", [Dump])),
    io:format("StringDump:~p~n", [StringDump]),
    SubStringDump = string:substr(StringDump, 4),
    io:format("SubStringDump:~p~n", [SubStringDump]),
    Ndump = concat(StringNumline, SubStringDump),
    io:format("Ndump:~p~n", [Ndump]),
    FineDump = Ndump--"\">>",
    io:format("FineDump:~p~n", [FineDump]),
    L1 = binary:split(Pars, <<"\r\n">>, [global]),
    io:format("L1=~p~n", [L1]),
    Check = lists:member(FineDump, L1),
    io:format("Check=~p~n", [Check]),

    if
        Check ->
            file:write_file("check.txt", "true\n", [append]);

        true ->
            file:write_file("check.txt", "false\n", [append])
    end.

这是代码的输出：

10> c(compare).         
{ok,compare}
11> compare:comparing().
Numline:1
StringNumline:"1"
StringDump:"<<\"hello\">>"
SubStringDump:"hello\">>"
Ndump:"1hello\">>"
FineDump:"1hello"
L1=[<<"0hello">>,<<"something">>,<<"anyword">>,<<"1hello">>,<<"2exercise">>,
    <<"2solution">>,<<"3test">>,<<"new">>,<<"4check">>,<<"4grade">>]
Check=false
ok

我在Check = lists:member(FineDump, L1) 行有问题。尽管 1hello 是列表的成员，但它总是错误的。我不知道哪里错了。它是函数列表：这个操作的成员吗？或者是否存在其他方法来查找字符串是否是列表的成员？我是 Erlang 的新手。

Answer 1

L1 是二进制文件列表，而FineDump 是字符串（Erlang 中的整数列表）。您需要将FineDump 转换为二进制文件才能使lists:member/2 调用正常工作。

这应该可行：

Check = lists:member(list_to_binary(FineDump), L1),

您似乎也以一种不必要的方式来做这件事。如果我理解逻辑很好，你就不需要所有的代码。您可以使用以下方法将 NumLine 和 Dump 连接成一个二进制文件：

X = <<(integer_to_binary(NumLine))/binary, Dump/binary>>

然后直接在lists:member中使用：

lists:member(X, L1)

1> NumLine = 1.
1
2> Dump = <<"hello">>.
<<"hello">>
3> <<(integer_to_binary(NumLine))/binary, Dump/binary>>.
<<"1hello">>