删除列表Erlang中的最后一个元素

Question

我需要删除列表中的最后一个元素。我在shell中运行此代码。

  

Erlang R16B03（erts-5.10.4）[source] [64-bit] [smp：4：4] [async-threads：10] [kernel-poll：false]

erl + pc unicode

ColumnListWithCommas = [<<"username">>,<<",">>,<<"password">>,<<",">>,
<<"created_at">>,<<",">>,<<"id">>,<<",">>,<<"email_hash">>,
<<",">>,<<"status">>,<<",">>,<<"mess_count">>,<<",">>].

lists:droplast(ColumnListWithCommas).
** exception error: undefined function lists:droplast/1

Answer 1

在Erlang R16B03中没有列表：droplast / 1。 你需要Erlang 17.0

你可以这样做：

1> A = [1, 2, 3, 4].
2> lists:reverse(tl(lists:reverse(A))).
[1,2,3]

Or

3> {L, _} = lists:split(length(A) - 1, A).

又一个方法。您可以从Erlang来源获取realization非常简单