正则表达式 [a-Z] 是否有效，如果是，那么它是否与 [a-zA-Z] 相同? [英] Is the regular expression [a-Z] valid and if yes then is it the same as [a-zA-Z]?

问题描述

正则表达式 [a-Z] 是否有效，如果是，那么它是否与 [a-zA-Z] 相同?请注意，在 [a-Z] 中，a 是小写字母，而 Z 是大写字母.

Is the regular expression [a-Z] valid and if yes then is it the same as [a-zA-Z]? Please note that in [a-Z] the a is lowercase and the Z is uppercase.

我收到了一些答案，指出虽然 [a-Z] 无效，但 [A-z] 有效(但不会与 [a-zA-Z] 相同)，这正是我想要的.因为我想知道是否可以用更紧凑的版本替换 [a-zA-Z].

I received some answers specifiying that while [a-Z] is not valid then [A-z] is valid (but won't be the same as [a-zA-Z]) and this is really what I was looking for. Since I wanted to know in general if it's possible to replace [a-zA-Z] with a more compact version.

感谢所有为答案做出贡献的人.

Thanks for all who contributed to the answer.

推荐答案

否，a (97) 高于 Z (90).[a-Z] 不是有效的字符类.然而 [A-z] 也不是等价的，但出于不同的原因.它会覆盖所有字母，但也会包括大写和小写字母之间的字符:[\]^_`.

No, a (97) is higher than Z (90). [a-Z] isn't a valid character class. However [A-z] wouldn't be equivalent either, but for a different reason. It would cover all the letters but would also include the characters between the uppercase and lowercase letters: [\]^_`.

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