正则表达式很懒，应该贪心 [英] Regex is behaving lazy, should be greedy

问题描述

我认为默认情况下，我的 Regex 会表现出我想要的贪婪行为，但是它不在以下代码中:

I thought that by default my Regex would exhibit the greedy behavior that I want, but it is not in the following code:

 Regex keywords = new Regex(@"in|int|into|internal|interface");
 var targets = keywords.ToString().Split('|');
 foreach (string t in targets)
    {
    Match match = keywords.Match(t);
    Console.WriteLine("Matched {0,-9} with {1}", t, match.Value);
    }

输出:

Matched in        with in
Matched int       with in
Matched into      with in
Matched internal  with in
Matched interface with in

现在我意识到，只要我按长度降序对关键字进行排序，就可以使它适用于这个小示例，但是

Now I realize that I could get it to work for this small example if I simply sorted the keywords by length descending, but

• 我想了解为什么 不能按预期工作，并且
• 我正在从事的实际项目 正则表达式中还有更多的单词， 重要的是要把它们留在里面 字母顺序.

• I want to understand why this isn't working as expected, and
• the actual project I am working on has many more words in the Regex and it is important to keep them in alphabetical order.

所以我的问题是:为什么这很懒?我该如何解决?

So my question is: Why is this being lazy and how do I fix it?

推荐答案

懒惰和贪婪仅适用于量词(?，*，+，{min,max}).交替总是按顺序匹配，然后尝试第一个可能的匹配.

Laziness and greediness applies to quantifiers only (?, *, +, {min,max}). Alternations always match in order and try the first possible match.

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