The true power of regular expressions

Modern regex engines like PCRE are far more powerful than the formal language theory definition of 'regular' suggests. Using recursive subpattern references and DEFINE-based named patterns, PCRE can match any context-free language — including well-formed HTML and most programming languages. It can also match at least some context-sensitive languages using lookahead/lookbehind assertions. Furthermore, adding backreferences makes regex matching NP-complete, demonstrated by encoding a 3-CNF SAT problem as a regex. The practical takeaway: use grammar-based regex with DEFINE blocks and named subpatterns for complex matching tasks, but prefer DOM parsers for general HTML processing.

Nguồn: https://www.npopov.com/2012/06/15/The-true-power-of-regular-expressions.html. 8sync News chỉ tóm tắt và dẫn link; bản quyền nội dung thuộc tác giả và nguồn gốc.