如何使用正则表达式匹配嵌套括号? [英] How can I match nested brackets using regex?

问题描述

正如标题所述，这是示例输入:

As the title says, here is an example input:

 (outer
   (center
     (inner)
     (inner)
   center)
 ouer)
 (outer
   (inner)
 ouer)
 (outer
 ouer)

当然，匹配的字符串将通过递归处理.

Of course, the matched strings will be processed by recursion.

我希望第一个递归匹配:

I want the first recursion to match:

 [
 (outer
   (center
     (inner)
     (inner)
   center)
 ouer),
 (outer
   (inner)
 ouer),
 (outer
 ouer)]

无需赘言……

推荐答案

许多正则表达式实现都不允许您匹配任意数量的嵌套.但是，Perl，PHP和.NET支持递归模式.

Many regex implementations will not allow you to match an arbitrary amount of nesting. However, Perl, PHP and .NET support recursive patterns.

Perl中的演示:

#!/usr/bin/perl -w

my $text = '(outer
   (center
     (inner)
     (inner)
   center)
 ouer)
 (outer
   (inner)
 ouer)
 (outer
 ouer)';

while($text =~ /(\(([^()]|(?R))*\))/g) {
  print("----------\n$1\n");
}

将打印:

----------
(outer
   (center
     (inner)
     (inner)
   center)
 ouer)
----------
(outer
   (inner)
 ouer)
----------
(outer
 ouer)

或者，相当于PHP:

$text = '(outer
   (center
     (inner)
     (inner)
   center)
 ouer)
 (outer
   (inner)
 ouer)
 (outer
 ouer)';

preg_match_all('/(\(([^()]|(?R))*\))/', $text, $matches);

print_r($matches);

产生:

Array
(
    [0] => Array
        (
            [0] => (outer
   (center
     (inner)
     (inner)
   center)
 ouer)
            [1] => (outer
   (inner)
 ouer)
            [2] => (outer
 ouer)
        )

...

说明:

(          # start group 1
  \(       #   match a literal '('
  (        #   group 2
    [^()]  #     any char other than '(' and ')'
    |      #     OR
    (?R)   #     recursively match the entir pattern
  )*       #   end group 2 and repeat zero or more times
  \)       #   match a literal ')'
)          # end group 1

编辑

注意@Goozak的评论:

EDIT

Note @Goozak's comment:

更好的模式可能是\(((?>[^()]+)|(?R))*\)(来自 PHP:递归模式).对于我的数据，当Bart遇到无嵌套的(长字符串)时，其模式使PHP崩溃.这个模式遍历了我所有的数据，没有问题.

A better pattern might be \(((?>[^()]+)|(?R))*\) (from PHP:Recursive patterns). For my data, Bart's pattern was crashing PHP when it encountered a (long string) without nesting. This pattern went through all my data without problem.

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