如何在VBA正则表达式中模拟后向行为? [英] How to simulate lookbehind in VBA regex?

问题描述

我正在尝试构建一个正则表达式模式，如果字符串以某些字符开头或包含非单词字符，则该模式将返回False，但是由于VBA的RegExp对象不支持向后看，所以我发现这很困难.唯一应该失败的单词字符前缀是B_，B-，b_，b-.

I'm trying to build a regex pattern that will return False if a string starts with certain characters or contains non-word characters, but because VBA's RegExp object doesn't support lookbehind, I am finding this difficult. The only word character prefixes that should fail are B_, B-, b_, b-.

这是我的测试代码:

Sub testregex()

Dim re As New RegExp

re.pattern = "^[^Bb][^_-]\w+$"

Debug.Print re.Test("a24")
Debug.Print re.Test("a")
Debug.Print re.Test("B_")
Debug.Print re.Test(" a1")


End Sub

我希望它返回:

True
True
False
False

但它返回

True
False
False
True

问题是模式会查找不在[Bb]中的字符，然后是不在[-_]中的字符，然后是一系列字字符，但是我想要的只是一个或多个字字符，这样，如果有2个或更多字符，则前两个不是[Bb][-_].

The problem is that the pattern looks for a character that's not in [Bb], followed by a character that's not in [-_], followed by a sequence of word characters, but what I want is just one or more word characters, such that if there are 2 or more characters then the first two are not [Bb][-_].

推荐答案

尝试匹配此表达式:

^([Bb][\-_]\w*)|(\w*[^\w]+\w*)$

...将与"B _"，"b _"，"B-"和"b-"或任何非文字字符匹配的内容.将成功匹配视为失败"，并且仅允许不匹配有效.

...which will match "B_", "b_", "B-" and "b-" or anything that's not a word character. Consider a successful match a "failure" and only allow non-matches to be valid.

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