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

没有列表:Erlang R16B03中的droplast/1.你需要Erlang 17.0

你可以做:

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).

还有一种方法.您可以从Erlang源代码中实现它非常简单