VBScript 的正则表达式负回溯替代方案 [英] Regular Expression Negative Lookbehind Alternative for VBScript

问题描述

由于 VBScript 不支持后视，我正在寻找替代解决方案.

Since VBScript doesn't support lookbehinds, I'm looking for an alternative solution.

我有字符串 '\E\F\'.

I have the string '\E\F\'.

我想用'~'替换\F\，但前提是它前面没有\E.

I want to replace \F\ with '~', but ONLY if it is not preceded by a \E.

替换后，我希望 '\E\F\' 为 '\E\F\'.

After the substitution, I want '\E\F\' to be '\E\F\'.

如果字符串是'randomText\F\'，我希望它在替换后看起来像'randomText~'.

If the string was 'randomText\F\', I would want it to look like 'randomText~' after the substitution.

解决方案:

我只是决定对它进行 StrReverse 并做一个负面的前瞻.这不是最优雅的解决方案，但在这种情况下似乎有效.

I just decided to StrReverse it and do a negative forward lookahead. It's not the most elegant solution, but it seems to work in this case.

Dim regEx, str1
str1 = StrReverse("The quick \F\ brown \E\F\ dog.")
Set regEx = New RegExp
regEx.IgnoreCase = True
regEx.Pattern = "\\F\\(?!E\\)"
regEx.Global = True
ReplaceTest = regEx.Replace(str1, "%")

推荐答案

VBScript 不支持外观-在断言背后.但是试试这个:

(^.?|[^\\].|\\[^E])\\F\\

或者这个:

(^.?|(?!\\E)..)\\F\\

将匹配替换为 $1~(第一个子匹配和 ~).

Replace the match with $1~ (first submatch and ~).

这里解释一下:一般有两种情况:如果\F\(^.?)前没有或只有一个字符，则一切正常.但是如果\F\之前至少有两个字符，我们需要确保这些字符不是\E.所以我们说，前面的两个字符要么是

Here’s an explanation: In general there are two situations: If there is no or just one character before \F\ (^.?), everything is ok. But if there are at least two characters before \F\, we need to make sure, that these characters are not \E. So we say, that the two preceeding characters are either

• 除\ 外的任何字符后跟任意字符([^\\].)，或
• \ 后跟除 E 之外的任何字符(\\[^E]).

• any character except \ followed by any arbitrary character ([^\\].), or
• \ followed by any character other then E (\\[^E]).

该构造确保允许除 \E 之外的所有其他组合.

That construct ensures that every other combincation except \E is allowed.

同样适用于第二个表达式.但是这里我们使用否定的前瞻断言来确保\F\之前的两个字符不是\E.

The same applies to the second expression. But here we use the negative look-ahead assertion to ensure that the two characters before \F\ is not \E.

这篇关于VBScript 的正则表达式负回溯替代方案的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！