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perl中有没有类似vim的\zs和\ze的功能? [复制链接]

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双子座
日期:2015-01-04 14:25:06
发表于 2013-10-15 12:37 |显示全部楼层
这样替换方便点

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发表于 2013-10-15 12:43 |显示全部楼层
查下 vim 的文档在Perl 里面叫环视吧
Look-Around Assertions

Look-around assertions are zero-width patterns which match a specific pattern without including it in $& . Positive assertions match when their subpattern matches, negative assertions match when their subpattern fails. Look-behind matches text up to the current match position, look-ahead matches text following the current match position.

    (?=pattern)

    A zero-width positive look-ahead assertion. For example, /\w+(?=\t)/ matches a word followed by a tab, without including the tab in $& .
    (?!pattern)

    A zero-width negative look-ahead assertion. For example /foo(?!bar)/ matches any occurrence of "foo" that isn't followed by "bar". Note however that look-ahead and look-behind are NOT the same thing. You cannot use this for look-behind.

    If you are looking for a "bar" that isn't preceded by a "foo", /(?!foo)bar/ will not do what you want. That's because the (?!foo) is just saying that the next thing cannot be "foo"--and it's not, it's a "bar", so "foobar" will match. Use look-behind instead (see below).
    (?<=pattern) \K

    A zero-width positive look-behind assertion. For example, /(?<=\t)\w+/ matches a word that follows a tab, without including the tab in $& . Works only for fixed-width look-behind.

    There is a special form of this construct, called \K , which causes the regex engine to "keep" everything it had matched prior to the \K and not include it in $& . This effectively provides variable-length look-behind. The use of \K inside of another look-around assertion is allowed, but the behaviour is currently not well defined.

    For various reasons \K may be significantly more efficient than the equivalent (?<=...) construct, and it is especially useful in situations where you want to efficiently remove something following something else in a string. For instance

        s/(foo)bar/$1/g;

    can be rewritten as the much more efficient

        s/foo\Kbar//g;

    (?<!pattern)

    A zero-width negative look-behind assertion. For example /(?<!bar)foo/ matches any occurrence of "foo" that does not follow "bar". Works only for fixed-width look-behind.

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日期:2015-01-04 14:25:06
发表于 2013-10-15 15:03 |显示全部楼层
zhlong8 发表于 2013-10-15 12:43
查下 vim 的文档在Perl 里面叫环视吧

多谢,搞定。
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