this post was submitted on 07 Oct 2023
93 points (97.9% liked)
Programming
17398 readers
106 users here now
Welcome to the main community in programming.dev! Feel free to post anything relating to programming here!
Cross posting is strongly encouraged in the instance. If you feel your post or another person's post makes sense in another community cross post into it.
Hope you enjoy the instance!
Rules
Rules
- Follow the programming.dev instance rules
- Keep content related to programming in some way
- If you're posting long videos try to add in some form of tldr for those who don't want to watch videos
Wormhole
Follow the wormhole through a path of communities !webdev@programming.dev
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Regular expressions are great and can always be matched in linear time with respect to the input string length.
The problem is that JS standard library RegExps aren't actually regular expressions, but rather a much broader language, which is impossible to implement efficiently. If RegExp switched to proper regular expressions, they would match much faster but supporting backreferences like /(.*)x\1/ would be impossible.
If you insist on the definition as it is in formal language theory.
In practice regex is widely used to mean the pattern matching thing that also supports back references.
Wikipedia suggests using the term "regular expressions" for the language theory thing and "regex" for the programming language (PCRE) thing. I agree and would even go further and say that any time one wants to refer to the concept as it is used in formal language theory they should explicitly specify that they are talking about the theoretical concept, not the regex implementation as it is found in most programming languages.