[英]How does this regex pattern work
I am learning regex and I am currently looking at this page http://regexone.com/example/0 I am following everything ok so far but I dont understand how this one works 我正在学习正则表达式,目前正在查看此页面http://regexone.com/example/0到目前为止,我一直在进行一切正常的操作,但我不了解此工作原理
^-?\d+(,\d+)*(\.\d+(e\d+)?)?$
It matches the following text: 它与以下文本匹配:
And skips this one: 并跳过这一步:
The solution explains it like this 解决方案这样解释
For the above example, the expression '^-?\\d+(,\\d+)*(.\\d+(e\\d+)?)?$' will match a string that starts with an optional negative sign, one or more digits, optionally followed by a comma and more digits, followed by an optional fractional component which consists of a period, one or more digits, and another optional component, the exponent followed by more digits.
对于上面的示例,表达式'^-?\\ d +(,\\ d +)*(。\\ d +(e \\ d +)?)?$'将匹配以可选负号,一个或多个数字开头的字符串, (可选)后跟一个逗号和多个数字,然后是一个可选的小数部分,该部分由一个句点,一个或多个数字以及另一个可选的部分组成,指数后面是更多的数字。
The * is where I get confused. *是让我感到困惑的地方。 I read it like this:
我这样阅读:
^ Start
-? Optional Negative
\d+ One or more digits
(,\d+)* Group-comma and one or more digits - the * confuses me here
(\.\d+(e\d+)?)? Optional group of full stop, one or more digits, another optional group of e and 1 or more digits
As I said the * confuses me. 正如我所说的,*使我感到困惑。 I think it is something to do with Variable content but I dont understand how it works.
我认为这与“可变内容”有关,但我不了解它的工作原理。
The *
is simply a quantifier that states: 'match 0 or more of the previous match', in this case (,\\d+)
. *
只是表示以下内容的量词:“匹配上一个匹配项0个或多个”,在这种情况下(,\\d+)
。
In this case, it would match something like: 在这种情况下,它将匹配以下内容:
,123,123,123,63,345,345,346,3245235,234 (of any length but similar pattern)
that means that zero
or more
times a group like this ,34
is allowed. 这意味着
zero
或more
次这样的组,34
是允许的。
group like ,34
or ,666
is represented as (,\\d+)*
,34
或,666
类的组表示为(,\\d+)*
so that it allows text 122,222,12 or 323,212,22 因此它允许文本122,222,12或323,212,22
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