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What is the procedure for conducting a negative look-ahead when the number of closing brackets is uncertain?

asked 2021-07-29 11:00:00 +0000

plato gravatar image

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answered 2021-10-22 05:00:00 +0000

woof gravatar image

When conducting a negative look-ahead with uncertain closing brackets, you can use a recursive pattern to match the opening bracket and any characters inside the brackets, then use the negative look-ahead to assert that the closing brackets do not immediately follow. Here's an example of the procedure:

  1. Start with the opening bracket, e.g., (
  2. Match any characters inside the brackets using a recursive pattern, e.g., (?:[^()]|(?R))*
    • [^()] matches any character that is not an opening or closing bracket
    • (?R) is a recursive reference that matches the entire pattern again
    • * allows for any number of characters inside the brackets, including zero
  3. Use a negative look-ahead to assert that the closing brackets do not immediately follow, e.g., (?!])
    • ] can be replaced with any closing bracket that you are trying to avoid
  4. Close the opening bracket, e.g., )

Putting it all together, the regex pattern for a negative look-ahead with uncertain closing brackets would look like this: (\((?:[^()]|(?R))*)(?!])\)

This pattern will match any opening bracket followed by any characters inside the brackets, as long as the closing brackets do not immediately follow. Note that this may not work for all cases, as it assumes that the opening and closing brackets are paired correctly. If there are unpaired brackets or other irregularities, a more advanced regex pattern may be required.

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Asked: 2021-07-29 11:00:00 +0000

Seen: 8 times

Last updated: Oct 22 '21