nested-reference – Tarik Billa

How does this regex find triangular numbers?

June 9, 2023 by Tarik

Explanation Here’s a schematic breakdown of the pattern: from beginning… | …to end | | ^(\1.|^.)+$ \______/|___match group 1 one-or-more times The (…) brackets define capturing group 1, and this group is matched repeatedly with +. This subpattern is anchored with ^ and $ to see if it can match the entire string. Group 1 … Read more

How can we match a^n b^n?

December 31, 2022 by Tarik

The answer is, needless to say, YES! You can most certainly write a Java regex pattern to match anbn. It uses a positive lookahead for assertion, and one nested reference for “counting”. Rather than immediately giving out the pattern, this answer will guide readers through the process of deriving it. Various hints are given as … Read more