regex - 正则表达式 [^\d\s] 和 [\D\S] 有什么区别

Question

有人可以解释 [^\d\s] 之间的区别吗？和 [\D\S] ?

来自 http://www.regular-expressions.info/shorthand.html 的描述不是很清楚:

Be careful when using the negated shorthands inside square brackets. [\D\S] is not the same as [^\d\s]. The latter matches any character that is neither a digit nor whitespace. It matches x, but not 8. The former, however, matches any character that is either not a digit, or is not whitespace. Because all digits are not whitespace, and all whitespace characters are not digits, [\D\S] matches any character; digit, whitespace, or otherwise.

他们对我来说似乎是一样的。或者我错过了什么？

Answer 1

[^\d\s]

将匹配不是数字或空格的单个字符。

[\D\S]

将匹配一个非数字或非空格的单个字符。

由于每个字符都不是数字或不是空格，因此第二个正则表达式将匹配任何字符。

相当于:

if (!(isdigit(c) || isspace(c))) ...

和

if (!isdigit(c) || !isspace(c)) ...

请注意，以下等价于第一个(根据德摩根定律):

if (!isdigit(c) && !isspace(c)) ...