How Can Regular Expressions Accurately Match Balanced Parentheses Within a Specific Function Call?

Regular Expressions for Precise Balanced Parenthesis Matching

This article addresses the challenge of accurately matching balanced parentheses using regular expressions, specifically within the context of a function call (e.g., funcPow). Standard regex approaches often fail to confine matching to the desired function call's scope.

The solution lies in a more advanced regex technique. The following expression uses named capture groups and balancing group constructs to achieve precise matching:

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

    \(                          # Opening parenthesis
        (?:                     
        [^()]                   # Match any character except parentheses
        |
        (?<open> \( )           # Match opening parenthesis, add to 'open' stack
        |
        (?<-open> \) )          # Match closing parenthesis, remove from 'open' stack
        )+
        (?(open)(?!))           # Assertion: 'open' stack must be empty
    \)                          # Closing parenthesis
", RegexOptions.IgnorePatternWhitespace);</code>

This regex uses a balancing group mechanism. (?<open> ( ) adds an opening parenthesis to a named capture group "open," acting like a stack. (?<-open> ) ) removes a parenthesis from the "open" stack for each closing parenthesis encountered. The conditional (?(open)(?!)) ensures that the match fails if the stack ("open") isn't empty at the end, guaranteeing balanced parentheses within the function call. This approach effectively restricts the match to the intended function call.

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