How Can I Use Regular Expressions to Match Only Balanced Parentheses in a String?

Regular Expression Tips: Perfect Matching of Balanced Parentheses

In the world of programming, balanced parentheses are crucial to ensuring code integrity. Regular expressions (RegEx) provide a powerful mechanism for identifying and validating balanced bracket pairs. However, creating a regular expression that accurately matches balanced brackets can be a complex task.

Consider the following regular expression:

<code>func([a-zA-Z_][a-zA-Z0-9_]*)\(.*\)</code>

This expression is designed to match the string "funcPow((3),2) * (9 1)". Ideally, it should only select "funcPow((3),2)"; however, it currently captures everything up to the last closing bracket, causing the match to not be as expected.

Solution for balanced matching:

Solving this problem requires a more advanced implementation that takes advantage of the power of regular expressions - capturing deletions. The following modified expression demonstrates how to achieve balanced bracket matching:

<code>var r = new Regex(@"
    func([a-zA-Z_][a-zA-Z0-9_]*) # 函数名

    \(                      # 开括号
        (?:                 
        [^()]               # 匹配所有非括号字符
        |
        (?<open> \( )       # 匹配'(', 并捕获到名为'open'的组中
        |
        (?<-open> \) )      # 匹配')', 并删除'open'组中的相应捕获
        )+
        (?(open)(?!))       # 如果'open'堆栈不为空，则匹配失败

    \)                      # 闭括号
", RegexOptions.IgnorePatternWhitespace);</code>

Explanation of balanced matching subgroups:

The key to balanced brackets lies in the following subgroups:

• (? ( ): Capture the opening bracket into a named capturing group called "open".
• (?<-open> ) ): Matches the closing bracket and removes the corresponding "open" capture.

No capturing clause: (?(open)(?!))

This conditional expression is used as a safety mechanism in case the "open" capture is not empty. If the "open" capture is still present, which means there are unmatched open brackets, expression matching fails.

By combining these techniques, you can create a regular expression that accurately matches balanced brackets and returns the desired match:

<code>"funcPow((3),2)"</code>

Master these advanced features of regular expressions and you can solve complex string processing challenges like balanced brackets elegantly and efficiently.

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