只有匹配時，如果兩者都是負向前瞻和Lookbehind失敗

Question

我試圖創建一個正則表達式來檢查句子中是否存在單詞，如果它沒有用單引號括起來。

我已經嘗試了不同的正則表達式，如：

(?<!')(?i:THEN)|(?i:THEN)(?! ') 

比賽 '那麼' | '那麼'，這不應該匹配。

(?<!')(?i:THEN)(?! ') or (?<!('))(?i:THEN)|(?i:THEN)(?!(')) 

匹配「然後」，這不應該匹配

我真的很堅持，因爲我不知道哪個正則表達式的作品。我也試過其他正則表達式，但它不匹配：

' then I jumped. 
He said then 'Wow'. 

一些輸入將不勝感激！

謝謝！

Answer 1

說明

此正則表達式匹配未用引號括起來的字then。

\bTHEN\b(?<!'\s*THEN(?=\s*')) 

一些語言不允許交替如\s?或\s*內lookbehinds。所以，如果你使用其中的一種語言，那麼你需要獲得關於測試空間的信息。

\bTHEN\b(?<!'\sTHEN(?=\s'))(?<!'THEN(?=')) 

例

現場演示

https://regex101.com/r/gS4zU8/1

then    matched 
'then   matched 
then'   matched 
'then' 
' then   matched 
then '   matched 
' then ' 
' then I jumped.  matched 
He said then 'Wow'. matched 
SthenS 

說明

NODE      EXPLANATION 
---------------------------------------------------------------------- 
    \b      the boundary between a word char (\w) and 
          something that is not a word char 
---------------------------------------------------------------------- 
    THEN      'THEN' 
---------------------------------------------------------------------- 
    \b      the boundary between a word char (\w) and 
          something that is not a word char 
---------------------------------------------------------------------- 
    (?<!      look behind to see if there is not: 
---------------------------------------------------------------------- 
    '      '\'' 
---------------------------------------------------------------------- 
    \s      whitespace (\n, \r, \t, \f, and " ") 
---------------------------------------------------------------------- 
    THEN      'THEN' 
---------------------------------------------------------------------- 
    (?=      look ahead to see if there is: 
---------------------------------------------------------------------- 
     \s      whitespace (\n, \r, \t, \f, and " ") 
---------------------------------------------------------------------- 
     '      '\'' 
---------------------------------------------------------------------- 
    )      end of look-ahead 
---------------------------------------------------------------------- 
)      end of look-behind 
---------------------------------------------------------------------- 
    (?<!      look behind to see if there is not: 
---------------------------------------------------------------------- 
    'THEN     '\'THEN' 
---------------------------------------------------------------------- 
    (?=      look ahead to see if there is: 
---------------------------------------------------------------------- 
     '      '\'' 
---------------------------------------------------------------------- 
    )      end of look-ahead 
---------------------------------------------------------------------- 
)      end of look-behind 
----------------------------------------------------------------------