Elixir从两个列表中删除常见元素

问题描述：

我想从列表a中删除列表b中的元素。
执行此代码后，列表a正在打印[1,2,3,4]。

I want to remove the elements found in list b from list a. The list a is printing [1,2,3,4] after execution of this code.

defmodule Test do
def listing do
    a = [1,2,3,4]
    b = [3,4,5,6]

    Enum.each b, fn elemB ->
        a = Enum.filter(a, fn(x) -> x != elemB == true end)
        #IO.inspect a
    end 
    IO.inspect a
end
end

Test.listing()

答

您不需要外部的 Enum.each ，可以通过枚举 a 并检查每个元素是否是 b 的成员：

You don't need that outer Enum.each, you can do it with a single filter by enumerating over a and checking each element to see if it is a member of b:

Enum.filter(a, fn el -> !Enum.member?(b, el) end)

输出：

[1, 2]

您当前的解决方案似乎试图修改 a ，但是这不起作用，因为Elixir具有功能且该功能不会产生副作用；每个 中的 a 与 a 不同>这是原始列表。

It looks like with your current solution you are trying to modify a but that won't work because Elixir is functional and the function can't have side effects; the a inside your each is not the same as the a that is the original list.

Elixir从两个列表中删除常见元素

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