ruby 中的/\p{Alpha}/i 和/\p{L}/i 有什么区别? [英] What's the difference between /\p{Alpha}/i and /\p{L}/i in ruby?
问题描述
我正在尝试在 ruby 中构建一个正则表达式来匹配 UTF-8 中的字母字符，例如 ñíóúü 等.我知道 /\p{Alpha}/i工作和 /\p{L}/i 也工作，但有什么区别?
I'm trying to build a regexp in ruby to match alpha characters in UTF-8 like ñíóúü, etc. I know /\p{Alpha}/i works and /\p{L}/i works too but what's the difference?
推荐答案
它们似乎是等效的.(有时，请参阅此答案的结尾)
They seem to be equivalent. ( sometimes, see the end of this answer)
似乎 Ruby 从 1.9 版开始就支持 \p{Alpha}.在 POSIX 中 \p{Alpha} 等于 \p{L&}(对于支持 Unicode 的正则表达式；见这里).这匹配所有具有大写和小写变体的字符(参见此处).不匹配大写字母(而它们将通过 \p{L} 匹配.
It seems like Ruby supports \p{Alpha} since version 1.9. In POSIX \p{Alpha} is equal to \p{L&} (for regular expressions with Unicode support; see here). This matches all characters that have an upper and lower case variant (see here). Unicase letters would not be matched (while they would be match by \p{L}.
这似乎不适用于 Ruby(我随机选择了一个阿拉伯语字符，因为阿拉伯语有一个unicase 字母表):
This does not seem to be true for Ruby (I picked a random Arabic character, since Arabic has a unicase alphabet):
\p{L}(any letter) matches.- Case-sensitive classes
\p{Lu},\p{Ll},\p{Lt}don't match. As expected. p{L&}doesn't match. As expected.\p{Alpha}matches.
这似乎很好地表明 \p{Alpha} 只是 Ruby 中 \p{L} 的别名.在 Rubular 上，您还可以看到 \p{Alpha} 在 Ruby 1.8.7 中不可用.
Which seems to be a very good indication that \p{Alpha} is just an alias for \p{L} in Ruby. On Rubular you can also see that \p{Alpha} was not available in Ruby 1.8.7.
注意 i 修饰符在任何情况下都无关紧要，因为 \p{Alpha} 和 \p{L} 都匹配大写和小写字符.
Note that the i modifier is irrelevant in any case, because both \p{Alpha} and \p{L} match both upper- and lower-case characters anyway.
啊哈，有区别！我刚刚找到了 这个 PDF 关于 Ruby 的新正则表达式引擎(从 Ruby 1.9 开始使用)如上所述).\p{Alpha} 无论编码如何都可用(如果不支持 Unicode，则可能只匹配 [A-Za-z])，而 \p{L} 特别是一个 Unicode 属性.这意味着，\p{Alpha} 的行为与 POSIX 正则表达式完全相同，不同之处在于这里对应于 \p{L}，但在 POSIX 中它对应于 <代码>\p{L&}.
A ha, there is a difference! I just found this PDF about Ruby's new regex engine (in use as of Ruby 1.9 as stated above). \p{Alpha} is available regardless of encoding (and will probably just match [A-Za-z] if there is no Unicode support), while \p{L} is specifically a Unicode property. That means, \p{Alpha} behaves exactly as in POSIX regexes, with the difference that here is corresponds to \p{L}, but in POSIX it corresponds to \p{L&}.
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