Assertion of the regular expression with Zero Width and assertion of the Regular Expression

Assertion of the regular expression with Zero Width and assertion of the Regular Expression

When learning the Regular Expression of. NET, I am confused about the assertion with Zero Width. I took some time to study and take a note.

 

Assertion Overview	(? <= Pattern )(? <! Pattern)STRING(? = Pattern )(?! Pattern): the relative position of various assertions. ? <LookbehindSTRING<Lookahead: NegativeSTRINGForward =: Positive, Positive, indicating matching ! : Negative, no, indicating no match
(? = Pattern)	Zero-width positive lookahead. If it is not a get match, search for it from the right of the string. It must match pattern. For example (? = 95 | 98 | NT | 2000) "can match" Windows "in" Windows2000 ", but cannot match" Windows "in" Windows3.1 ". Pre-check does not consume characters, that is, after a match occurs, it will continue fromSTRINGThen start the next matching search, instead of starting from after pattern. Same below
(?! Pattern)	Zero-width negative lookahead (0-width negation). If it is not a get match, it is searched from the right side of the string and must not match pattern. For example, "Windows (?! 95 | 98 | NT | 2000) "can match" Windows "in" Windows3.1 ", but cannot match" Windows "in" Windows2000 ".
(? <= Pattern)	Zero-width positive lookbehind. If the string is not retrieved, the string must match pattern on the left .. For example, <= 95 | 98 | NT | 2000) Windows can match Windows in 2000Windows, but cannot match Windows in 3.1Windows ".
(? <! Pattern)	Zero-width negative lookbehind (Zero-width negative), non-get match, search from the left side of the string, must not match pattern. For example, "(? <! 95 | 98 | NT | 2000) Windows can match "Windows" in "3.1Windows", but cannot match "Windows" in "2000Windows ".