在Elixir中将字符串与列表中的随机值进行比较时出现问题

Question

defmodule Takes do
  def rnd do
    lst = ["rock", "paper", "scissors"]
    tke = Enum.take_random(lst, 1)
    IO.puts "#{tke}"
    IO.puts "#{List.first(lst)}"
    IO.puts "#{tke == List.first(lst)}"
  end
end

Takes.rnd

输出始终为false。为什么？

Answer 1

您使用的是Enum.take_random，它返回一个列表。当然，它永远不会与字符串匹配。

对您的代码进行了一些改进：

defmodule Takes do
  def rnd do
    lst = ["rock", "paper", "scissors"]
    tke = Enum.random(lst) # this will return a single item, not a list
    IO.inspect(tke) # no need for string interpolation, also if you used inspect before
                    # you would see that `tke` was indeed a list
    IO.puts hd(lst) # hd and tl are both very useful functions, check them out
    tke == hd(lst)  # the last statement in a function is the return value (and when
                    # using `iex` will be printed)
  end
end

Takes.rnd