问题描述
我有以下文字
tooooooooooooon
根据我正在阅读的这本书，当?出现在任何量词之后时，它就变得不贪婪.
According to this book I'm reading, when the ? follows after any quantifier, it becomes non greedy.
我的正则表达式to*?n仍返回tooooooooooooon.
My regex to*?n is still returning tooooooooooooon.
它应该返回ton不是吗?
知道为什么吗?
推荐答案
正则表达式只能匹配实际存在的文本片段.
A regular expression can only match a fragment of text that actually exists.
因为子字符串"ton"在字符串中不存在，所以不能是匹配的结果.匹配项只会返回原始字符串的子字符串
Because the substring 'ton' doesn't exist anywhere in your string, it can't be the result of a match. A match will only return a substring of the original string
要清楚，如果您使用下面的字符串，请加上一个额外的'n'
To be clear, if you were using the string below, with an extra 'n'
toooooooonoooooon
此正则表达式(不指定'o')
this regular expression (which doesn't specify 'o's)
t.*n
将匹配以下内容(在"n"之前尽可能多的字符)
would match the following (as many characters as possible before an 'n')
toooooooonoooooon
但是正则表达式
t.*?n
仅匹配以下内容(在"n"之前尽可能少的字符)
would only match the following (as few characters as possible before an 'n')
toooooooon
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