algorithm - 数字解释为大写字符

Question

我正在 exercism.io 上关注一个练习

我是 Elixir 社区和语言的新手，我正在按照 Elixir 路径进行训练。无论如何，我正在碰壁，我不明白为什么。

练习如下:

Bob is a lackadaisical teenager. In conversation, his responses are very limited.

Bob answers 'Sure.' if you ask him a question.

He answers 'Whoa, chill out!' if you yell at him.

He answers 'Calm down, I know what I'm doing!' if you yell a question at him.

He says 'Fine. Be that way!' if you address him without actually saying anything.

He answers 'Whatever.' to anything else.

Bob's conversational partner is a purist when it comes to written communication and always follows normal rules regarding sentence punctuation in English.

所以我的代码是这样的:

defmodule Bob do
   def hey(input) do
     input = String.trim(input)
     is_empty? = &(String.length(&1) == 0)
     is_upcase? = &(&1 == String.upcase(&1))
     is_question? = &(String.ends_with?(&1, "?"))
     cond do
       is_question?.(input) && is_upcase?.(input) ->
         "Calm down, I know what I'm doing!"
       is_question?.(input) ->
         "Sure."
       is_empty?.(input) ->
         "Fine. Be that way!"
       is_upcase?.(input) == true ->
         "Whoa, chill out!"
       true ->
         "Whatever."
     end
   end
end

为了验证练习是否正确，我们有一个非常好的测试套件。两个测试没有通过:

  1) test only numbers (BobTest)
     bob_test.exs:71
     Assertion with == failed
     code:  assert Bob.hey("1, 2, 3") == "Whatever."
     left:  "Whoa, chill out!"
     right: "Whatever."
     stacktrace:
       bob_test.exs:72: (test)

......

  2) test question with numbers (BobTest)
     bob_test.exs:76
     Assertion with == failed
     code:  assert Bob.hey("4?") == "Sure."
     left:  "Calm down, I know what I'm doing!"
     right: "Sure."
     stacktrace:
       bob_test.exs:77: (test)

.......

Finished in 0.09 seconds (0.08s on load, 0.01s on tests)
15 tests, 2 failures

Randomized with seed 683339

所以我的问题如下:为什么即使我通过 String.downcase("foo") 将数字解释为大写字母？

Answer 1

String.upcase/2返回将字母转换为大写的字符串。数字没有大小写的概念。

您的代码 &1 == String.upcase(&1) 正在将字符串与自身的大写版本进行比较。对于不包含字母的字符串，它们是相同的。例如 "1"== String.upcase("1")。

错误在于您的 is_upcase? 函数实际上并未检查字符串是否包含大写字符。如评论和 this answer 中所述您可以添加正则表达式来检查字符串是否确实包含大写字符。

顺便说一句，使用以 ? 结尾的函数时，惯例是不要在它们前面加上 is_ 前缀。所以你的函数最好命名为 upcase?。

upcase? = &(&1 == String.upcase(&1) && String.match?(&1, ~r/\p{Lu}/u))

最好明确检查大写字符，因为有超过 100,000 个 unicode“字母”，但只有不到 2,000 个被认为是大写字母(测试的大小写不可知示例:"闻いテる? ").